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1. Figure 2 2 Direct Connectivity In this solution case 1 in Figure 2 1 Architectures of Internet Connectivity and Figure 2 2 Direct Connectivity both communication end points are directly connected via a telephone line In most cases the microcontroller acts as web server and the host computer dials to the embedded device There are only rare cases where the embedded device dials to the remote server However client connections in the presented way are comfortable for debugging purpose but for runtime conditions such a client is nearly not to be seen Designer Reference Manual DRM049 Rev 0 22 Connecting Embedded Applications to the Internet MOTOROLA For More Information On This Product Go to www freescale com DRM049 Rev 0 Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Internet Connectivity In most cases of direct connectivity there is no advantage in using standardized internet protocols and most systems work with proprietary protocols with minimum overhead So in proper wording this is no internet connectivity Table 2 1 SWOT Analysis of Direct Connectivity Without Internet Protocols However the use of internet protocol case 2 in Figure 2 1 Architectures of Internet Connectivity brings standardization with it This allows the use of internet based development and application tools The simplest implementation of internet connectivity is based on serial li
2. Basics of Implementation Layered Protocol Models user dale ayer7 Host A definition of the services provided by the layer 7 Host B uger data communication partner for each individual Application p dt esses application Program ceca Application ayer 6 tl layer 6 tl definition of the structures for user data with Presentation g sessesee regard to formatting sess Presentation ayer 5 tl layer 5 fl creation and removal of logical channels in Session g dl sesso PUysical transport systems unn Session ayer 4 fl layer 4 fl control of data stream by providing error Transport free logical channels Transport layer 3 tl layer 3 fl Definition of a path from end to end routing Network addressing Network ensuring correct data stream from point to layer 2 fl point by definition of a data format for layer 2 fl channel coding medium access control Data Link gc eiisiccccecvisantavsavsaclacalcatesnuitsencdivenceste Data Link layer 1 tl definition of mechanical and electrical Physical properties of the transport medium J Physical ogical data flow physical data flow Figure 3 1 ISO OSI Communication Layer Protocol The OSI reference model is a conceptual model composed of seven layers each specifying particular network functions It is now considered the primary architectural mode
3. For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Socket Interface STA TCP FIN WAIT2 Segment received FIN Actions send acknowledgement for the FIN segment 6 6 5 3 Transmission of segments An application can transmit data to a connected peer with the function call soc_write only when the socket is in STA _TCP_ ESTABLISHED state and there is no data waiting to be acknowledged The application data is copied into the data array of the socket s out buffer st_buf index cData before building the TCP header The TCP segments are stored in the out buffer as shown in Figure 6 14 TCP Segment Stored in st_buf index cData net_but cData cTOretr iTOend iDataLen tcphdr cTCPd TCP data TCP header TCP data length retransmission trigger value numbers of remaining retransmissions Figure 6 14 TCP Segment Stored in st_buf index cData The variable iDataLen stores the actual length of the TCP data as the TCP header does not provide such a field The function calls are shown in Figure 6 15 Function Calls Caused by soc_write DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 93 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter soc_write tcp_write buf_write TCP_H buf_write DATA ip_b
4. ea Co XK active client host 2 lt F active IP address 193 196 182 233 CSG active _ HTTP client port 1043 eet XT aive _ Figure 3 6 Ports and Sockets for Concurrent Servers TCP manages the connection between the communication channel and the application program in the hosts of both sides via ports A port is defined as a 16 bit number representing a field in the TCP header In dependence of this destination port number the receiving host passes the received data to the relevant application program Designer Reference Manual DRM049 Rev 0 40 Basics of Implementation MOTOROLA For More Information On This Product Go to www freescale com DRM049 Rev 0 Freescale Semiconductor Inc Basics of Implementation Ports and Sockets In addition to the concept of ports the socket approach is of key importance for concurrent servers A socket is a TCP communication end point which is identified by the triple e IP address of the opposite communication end point e TCP port number of the opposite communication end point and e TCP port number of the own communication end point This triple allows the unique identification of separate end points in the same and in different client hosts In this concept of concurrent servers a generalized TCP server socket with dummy information of the opposite communication end point is always waiting for packets with a matching destination port number This socket is called
5. 2 1 3 Embedding and Unifying Internet Connectivity and Web Services Internet connectivity gives access to a ubiquitous network of highest availability and reasonable performance at lowest cost This especially holds true for target oriented microcontroller based embedded systems However connectivity infrastructure is only the starting point for inter operability and portability A unified approach at application level OSI level 7 is the next step Its broad acceptance in the office and infotainment world its flexible design and its efficient implementation makes Hypertext Transfer Protocol HTTP the main contender for automation and control 2 1 4 Breaking the Embedded Isolation Inter operability is even more questioned against the background of traditional dedication of embedded solutions when optimized software hardware co design and cost efficiency play a major role However embedded internet calls for open systems and comprehensive inter operability through all levels of communication models A unified data flow from enterprise resource planning ERP and management information systems MIS to production planning systems PPS and field control is envisaged 2 1 5 Leveraging Security If security is of high value for desktop computing this holds true for embedded computing where production facilities and other hardware equipment is at risk Therefore security has to be at its maximum Designer Reference Manual DRM049
6. Rev 0 20 Connecting Embedded Applications to the Internet MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet System Design 2 2 System Design A typical embedded internet device may it be a highly integrated microcontroller uC or a digital signal processor DSP must handle at least two tasks e It has to control the system it is embedded in This functionality often requires real time operation of the device e It has to provide the internet connectivity Therefore a TCP IP protocol suite has to run on the device This protocol usually requires a powerful processor a complete operating system and a large amount of memory to function Depending on the target hardware as well as the complexity of the problem the developer has to decide whether to use an operating system According to market analysis more than 75 of the Embedded Applications use operating system OS This OS may be proprietary free or commercial At the time being only few OS provide a TCP IP protocol suite However an 8 or 16 Bit Microcontroller may not have enough resources for the implementation of an operating system No OS applications can be found in less complex applications often using small microcontrollers with strict hardware and runtime restrictions The choice of writing standalone code is often made in order to optimize memory usage code
7. a reaction is prepared depending on the protocol stack s settings and the packet s data mostly combined with an answer generated If the header indicates a higher layer to be responsible for the data and if the current layer s link is established this layer is to be informed about the availability of new data In all other cases the data are discarded This behavior allows a big inter operability of different networking media because the packets may be re packed for transport on different media In Figure 3 3 HTTP Packets Via a Serial Link Takes 51 Bytes Plus a Variable HTTP Header a part of a web page is shown encapsulated in a HDLC frame 3 4 Client Server Model DRM049 Rev 0 The client server model is basic for internet applications A client forms a request which is processed and answered by the client Figure 3 5 Client Server Model Thus the client server model sets requirements for the servers because a server application cannot be started on demand but has to be available and accessible at any moment of time For this IP address and TCP port have to be known However work arounds for use in practical life are possible see Figure 2 6 Communication Initiation of the emBETTER Implementation request response Figure 3 5 Client Server Model This model sometimes called application server model 2 is one of the fundamental principles of the Internet It assumes that a server being reachable via I
8. miconductor Inc Freescale Se Freescale Semiconductor Inc eto oye schon eee sohocti digital dna intelligence everywhere Internet Connectivity with HCS12 16 bit Microcontroller using the ACP Reference Design Designer Reference Manual M68HC 12 Microcontrollers DRM049 Rev 0 09 2003 MOTOROLA COM SEMICONDUCTORS For More Information On This Product Go to www freescale com Freescale Semiconductor Inc For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Internet Connectivity with HCS12 16 bit Microcontroller using the ACP Reference Design Designer Reference Manual Rev 0 by Dr Gerald Kupris Motorola SPS Munich Germany Harald Kreidl Motorola SPS Munich Germany Dirk Lill Steinbeis Transfer Centre Embedded Design and Networking University of Cooperative Education Loerrach Germany Prof Dr Ing Axel Sikora Steinbeis Transfer Centre Embedded Design and Networking University of Cooperative Education Loerrach Germany DRM049 Rev 0 Designer Reference Manual MOTOROLA 3 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Rev 0 4 MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 DRM049 Rev 0 Section 1 Section
9. Dynamic generation of content possible Supports multiple incoming connections at a time defined by CLIENT MAX CNT in http h Possibility of storing files in a file system with directories http c holds the implementation of the HTTP server The contents such as HTML files or graphics are placed in html c Designer Reference Manual DRM049 Rev 0 96 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Hypertext Transfer Protocol The HTTP server must be called periodically out of the main application loop with the function http _entry The non blocking functionality is provided through state machines The first state machine controls the HTTP server function if it is not possible to open a socket and to listen on the default HTTP port 80 The second state machine handles the acceptance of incoming requests and the phases of data exchange between the remote hosts and the different local sockets These two state machines are realized in http _entry Further state machines implemented in different procedures called by http entry control the processing of incoming data and the choice of the right web pages to transmit 6 7 2 Setup of the HTTP Server In this section the settings are explained that have to be modified to enable the HTTP server to provide the right objects upon request As mentio
10. www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 6 1 Introduction Section 6 Layer Implementation of emBetter This chapter gives an overview of the implemented protocols The modules in which the different protocol layers are implemented are described with their functional structure Beginning with the functions on the lowest layer of the OSI reference model the implementation is depicted layer by layer The most challenging step at the integration of emBetter into an application is the adaptation of the lower layer functionality to the user s environment Adaptation in higher layers is mostly intended to raise the performance of the protocol stack 6 2 Modem Communication 6 2 1 Overview Modems are the predominant way to connect to the Internet in the private environment which is proved by a range of 79 of all Internet connections in Germany in 2001 9 But in the embedded environment they are rarely utilized because of the wide range of different modem types in contrast to quasi standard types of Ethernet controllers On the ACP reference design alarm control panel w5 there is implemented a socket modem SC336H1 from Multi Tech It is also possible to connect a serial GSM modem to the RS232 interface of the ACP to be independent from a phone line 6 2 2 Files Enabling the Modem Communication DRM049 Rev 0 In this implementation the physical communication is separate
11. 1 on port 1080 received PPP packets received 9 sent 9 PPP packets received 10 sent 9 IP Datagram receivedIP Datagram length 29 IP Datagram length 33 IP Prot ID 1 IP UDP packet received Application UDP packet with data length 1 on port 1080 received PPP packets received 11 sent IP Datagram receivedIP Datagram length 68 IP Datagram length 64 IP Prot ID 1 ICHP packet received ECHO IP ICMP IP ICMP 1 Verbunden 00 57 02 Autom Erkenn 192008N 1 AF GROSS NF Aulzeichnen Druckerecha a Figure 7 2 Information Provided on Debug Interface DRM049 Rev 0 Designer Reference Manual MOTOROLA Test environment 111 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment 7 3 Simulation environment 7 3 1 Overview The Full Chip Simulation FCS included in Metrowerks CodeWarrior 3 0 is a high performing tool for developing and testing software for the HCS12 CPU It allows simulation the microcontroller as a whole including for example the pin signals and CPU cycles The different components of the simulator debugger enable very detailed control which would not be possible using an external microcontroller connected via a target interface This chapter describes the setup of the system with the emBetter protocol suite for FCS Furthermore some of the components included in Metrowerks CodeWarrior are presented with their use for debug
12. 24 bytes of RAM for saving the socket s information and a variable space for the in and out buffers The structure of a socket presents as following Designer Reference Manual DRM049 Rev 0 84 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Socket Interface struct socket UINTS cType socket type UDP or TCP UINTS cState connection state of the socket struct sockaddr sk remote IP address local and remote port number UINTS cProtState state of the protocol e g TCP UINT32 1Seq the sequence number of the packet sent UINT32 lack the last acknowledged byte of data UINT16 iTick the number of ticks until a new retransmission UINTS cRetr number of retransmissions allowed UINTS cDatalIn refers to a buffer with incoming data UINTS cDataOut refers to a buffer with outgoing data DRM049 Rev 0 Figure 6 9 emBetter Socket Structure The variable cState has to be distinguished from cProtState Whereas cState keeps track of the overall status of the socket such as soc_bind whereas cProtState stores actual status in the TCP state machine emBetter sockets may run UDP or TCP In both cases they offer the following function call pattern e soc_socket e soc_bind e soc_listen only for TCP in case of TCP server
13. Cases The released version 1 1 of emBetter with ACPRD corresponds to case 5 in Figure 2 1 Architectures of Internet Connectivity However Designer Reference Manual DRM049 Rev 0 30 Connecting Embedded Applications to the Internet MOTOROLA For More Information On This Product Go to www freescale com DRM049 Rev 0 Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Internet Connectivity additional modules are available at STZEDN w2 to cover other used cases e The inclusion of Ethernet module leads to case 4 in Figure 2 1 Architectures of Internet Connectivity e A VPIl compliant portal server w10 corresponds to case 6 in Figure 2 1 Architectures of Internet Connectivity Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 31 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Designer Reference Manual DRM049 Rev 0 32 Connecting Embedded Applications to the Internet MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 3 1 Overview Section 3 Basics of Implementation Three overall paradigms influence the implementation of embedded internet connectivity e The distribution of information into separate packets whi
14. FRAME is cyclically checked by the ppp _ entry function Having received a new frame the appropriate function for the packet s layer information is called see Figure 5 7 Call Structure of Function ppp_entry A detailed description of PPP can be found at 1 For authentication two general approaches can be distinguished a two way handshake protocol such as Password Authentication Protocol PAP and a three way handshake protocol such as Challenge Authentication Protocol CHAP in its various implementations 6 3 2 PPP State Machine DRM049 Rev 0 The state machine envisaged for PPP in RFC1661 11 contains five states However for the upper layers such as IP it is only relevant to know whether a network connection is available or not Therefore the PPP state machine of emBetter contains only two states net work or no network see Figure 6 5 The Simplified PPP State Machine The internal states of no network are realized within ppp receive NO NETWORK CARRIER cAuthOK LOST PPP_Close TRUE oD NETWORK Figure 6 5 The Simplified PPP State Machine Designer Reference Manual MOTOROLA Layer Implementation of emBetter 73 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter 6 3 3 Negotiation of LCP Options The Link Control Protocol offers a big variety of
15. HTML Page 100 HTTP Functions for Dynamic Content 101 Function Template for Generating Dynamic Content 102 SMTP Communication Between Mail Client and Mail Server 104 Non blocking Implementation of SMTP 105 Proprietary UDP Client Software 00005 107 Test Environment for the emBetter Suite 110 Information Provided on Debug Interface 111 Settings for the Terminal scccrcecceereiaind nd ieee sues 114 Data in the Command Window 0000e0e 114 Metrowerks Inspector Component 0005 115 Proiler Window cci 8454 praris ee eR et aeai 116 Code Coverage Information n anaana aaan 117 DRM049 Rev 0 12 List of Figures MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 DRM049 Rev 0 Table 2 1 2 2 2 3 2 4 2 5 2 6 5 2 List of Tables Title Page SWOT Analysis of Direct Connectivity Without Internet FOCIS peepee dws bo ee ce E bk tia ase a dees 23 SWOT Analysis of Direct Connectivity Without Internet Pe sererai aR eee ee 24 SWOT Analysis of Gateway based Connectivity With Internal Use of Internet Protocol and Ethernet 26 SWOT Analysis of Gateway based Connectivity With Internal Use of Non internet Protocols 00002 eee 27 SWOT Analysis of I
16. In any other case the operations depend on the current state of the socket The state of the socket is registered in stSocket cProtState The states in emBetter defined in socket c see Figure 6 13 The Possible States for TCP Sockets are compliant to the states of the TCP state machine specified in 3 2 Packet Switching of RFC 793 11 Designer Reference Manual f STA_TCP_ESTABLISHED ITA _TCP_SYN_SENT TA _TCP_SYN_RECY TA _TCP_FIN_WAIT1 ITA _TCP_FIN_WAIT2 STA_TCP_TIME_WAIT STA_TCP_CLOSED STA_TCP_CLOSE_WAIT STA_TCP_LAST_ACK STA_TCP_LISTEN STA_TCP_CLOSING STA_TCP_ESTAB DATA Figure 6 13 The Possible States for TCP Sockets DRM049 Rev 0 90 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Socket Interface The state STA_TCP_ESTAB DATA is an additional state indicating that the socket is established and that incoming data is waiting to be examined by the application layer The following tables follow the different states of the TCP state machine The respective actions are briefly described The states appear in the same order as implemented in tcp handler STA TCP LISTEN Segment received Actions STA_TCP SYN RECV SYN retrieve ast_buf element stores information such as source address source port and sequence number in the st_buf element sets socket in STA _T
17. Motorola Application Note AN2304 D 7 2002 Sikora A Brugger P Virtual Private Infrastructure An Industry Initiative for Unified and Secure Web Control with Embedded Devices 9th IEEE International Conference on Emerging Technologies and Factory Automation ETFA 2003 Lisbon Portugal 16 19 September 2003 Sikora A Embedded Applikationen im Internet Teil 1 Ubersicht Uber Vor und Nachteile von vernetzten Anwendungen Elektronik 22 2000 S 90 102 Teil 2 Implementierungen Elektronik 23 2000 S 164 169 Stevens W R TCP IP Illustrated Volume 1 The Protocols Addison Wesley 1994 ISBN 0 201 63346 9 Stevens W R Wright G R TCP IP Illustrated Volume 2 The Implementation DRM049 Rev 0 120 Sources MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Sources Literature Addison Wesley 1995 ISBN 0 201 63354 X Stevens W R TCP IP Illustrated Volume 3 TCP for transactions HTTP NNTP 9 Tanenbaum A Computernetzwerke 3rd ed Pearson Studium 2000 ISBN 3 8273 7011 6 DRM049 Rev 0 Designer Reference Manual MOTOROLA Sources 121 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Rev 0 122 Sources MOTOROLA For More Information On This Product Go to www freescale com Freescale Semicon
18. Rev 0 The software was originally developed using a M68EVB912DP256 and an external Zyxel PC modem In order to use the M68EVB912DP256 in the demonstration and development setup some modifications have to be implemented in the original Evaluation Board The MC9S12DP256 provides two serial communication interfaces SCIO and SCI1 SCIO was used as modem interface Since SCIO delivers only the Tx data and Rx data signals PORT A was configured as general purpose O to receive the signal CD respectively DCD data carrier detect and to drive the signal DTR data terminal ready for full communication to the modem An additional RS232 level shifter circuit was mounted on the evaluation board to drive SCIO and provide a fully specified RS232 interface to the modem Designer Reference Manual MOTOROLA Test environment 109 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment The second serial communication interface SCI1 of the MC9S12DP256 is used in conjunction with the RS232 level shifter which is already mounted on the M68EVB912DP256 Evaluation Board On SCI1 some Debug Information is delivered to a standard terminal This additional Debug Information greatly simplifies the process of software development Figure 7 1 Test Environment for the emBetter Suite Furthermore some smaller changes have to be made to the used software e The DELAY function has to be adapt
19. SAP Data Link S__ y Data Link oz i y SDU Physical Physical Flow Physical Figure 3 4 The Information Flow in the Layered Model 9 3 3 2 2 Horizontal communication of Internet Protocols The communication with the same layer on the opposite machine is implemented via service primitives These primitives can be arranged in four classes as request indication response and confirmation If the protocol utilized is reliable all classes of service primitives are adopted non reliable protocols only use the request and indication classes The protocol layers below the concerned layer are transparent to the protocol In order to achieve this transparency an encapsulation technique is adopted that provides a header for every layer passed This header contains information about the destination protocol layer the communication partners and information for data consistence At the receiving side these fields are analyzed and removed If the header information is correct the data inside the packet are afterwards treated depending on link status and protocol information of the header If the header information shows that the data are meant for the current layer Designer Reference Manual DRM049 Rev 0 38 Basics of Implementation MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation Client Server Model
20. Segment Processing that are needed for further processing are stored in the following local variables Table 6 6 Header Fields Used for TCP Segment Processing Header field Variable name length bit Sequence number ISeq 32 Header length IAck 32 TOS stFlags 16 Other fields and options are ignored Designer Reference Manual MOTOROLA Layer Implementation of emBetter 89 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter There are two types of segments that are handled regardless of the state of the socket A segment with the reset flag set RST sets a socket back regardless of the state of the socket Releasing the buffers and setting cProtState to STA_TCP CLOSED do this Server sockets of which cState is set to STA_SOC_BIND showing that they are expecting incoming connections are reset to STA_TCP LISTEN After resetting the socket the handler returns If the acknowledge flag is set in an incoming TCP segment and there is a buffer with outgoing data associated to the buffer the buffer can be released since the data was acknowledged of the connected peer Since the out buffer size is relatively little it is assumed that the connected peer acknowledged all data Statistics show that most TCP advertise a window size of 8KB 16KB or 32KB 13 However in the embedded world the length of data does not reach these values
21. Socket interface a TCP UDP Transport Internet gt TCP IP stack IP ICMP Data link interface A lt o oN lt z 3 Datalink S EN Q lt L Physical S Network interface lm T j a OH Media 2 Su J o Wy Ww lt Figure 5 4 Main Software Interfaces Figure 5 4 Main Software Interfaces shows the level of the two interfaces in the TCP IP reference model Further descriptions of the interfaces can be found in chapters 6 3 7 and 6 6 5 2 4 Integration of emBetter in an Application emBetter is specified to work without operating system Therefore the emBetter software must be included in the main loop of an application and it must be ensured that the entry function of emBetter is called frequently emBetter is implemented in a non blocking way so that the CPU is occupied only for a short time slice The initialization routine of emBetter software has to be called before entering the main loop emBetter occupies the serial communication interface SCI interrupt service routine of the interface that the modem is connected to An example implementation of the emBetter software into a main loop is shown in Figure 5 5 Main Software Interfaces Designer Reference Manual DRM049 Rev 0 54 Overall Implementation of emBetter MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Exception Handling Metrowerks CodeWarrior
22. Terminal connects the simulated microcontroller with the external modem Having enabled the Show Protocol option the characters received and transmitted can be observed in the command window This can DRM049 Rev 0 Designer Reference Manual MOTOROLA Test environment 113 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment obviously not replace a tool for inspecting internet packets but as these tools commonly do not provide information about raw SCI data the Terminal can fill this gap as already the modem initialization strings can be checked for the modem s answers Figure 7 4 Data in the Command Window Communication Device Specification Eg IV Use Serial Port M Redirect Simulator SCIO to COM Communication Device comi 19200 Baud Rate Cancel Help Figure 7 3 Settings for the Terminal T Command of x E TERMINAL Open serial port on COML baudrate 19200 STARTED RUNNING TERMINAL Send character TERMINAL Send character TERMINAL Send character TERMINAL Send character TERMINAL Send character TERMINAL Send character TERMINAL Send character TERMINAL Send character TERMINAL Send character i TERMINAL Send character TERMINAL Send character STOPPING Figure 7 4 Data in the Command Window 7 3 3 2 Inspector The Inspector window see Figure 7 5 Metrowerks Inspector Component informs ab
23. a passive ademon ora server socket When a matching packet is detected a new socket is generated This new active socket is copy of the original passive socket with the information of the opposite communication end point This active end point processes the communication When the communication is finished the active socket is deleted When the passive socket detects a second packet with a matching destination port number but different information of the opposite communication end point it generates a second active socket Designer Reference Manual MOTOROLA Basics of Implementation 41 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation Designer Reference Manual DRM049 Rev 0 42 Basics of Implementation MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Section 4 Design Techniques for emBetter 4 1 Overview The implementation of the TCP IP based protocol on a microcontroller with limited resources call some dedicated design techniques This holds true for the memory management the function interfaces and the blocking functions 4 2 Zero copy Approach The layered protocol model implies two major disadvantages Each protocol layer adds its own control information in a header leading to additional data to be transmitted As the majority of th
24. address gt Receive 250 REDY Send MAIL From lt sender gt Receive 250 RCV_STAT_ RCPT Send RCPT To lt recipient gt Receive 250 Send DATA DTCM Receive 354 Send Mail subject Header finished STRING_STAT_ cStringS STRING_STAT_0O cStringS 4 g STRING_STAT_1 3 cStringS t STRING_STAT_2 cStringS A t STRING_STAT_3 t cStringS v m STRING_STAT_4 cStringS v m STRING_STAT_5 cStringS 4 g Send Mail content Receive 221 Send QUIT Close Socket STRING_STAT_6 cStringS AA STRING_STAT_7 1 cStringS STRING_STAT_8 Figure 6 22 Non blocking Implementation of SMTP 6 9 6 Number of Strings Sent DRM049 Rev 0 During standard data transmission packets are transmitted from the client to the server The last packet is finished with a single in a line emBetter SMTP client transmits these packets by directly calling al al al al al al al al al TRING_STAT_O TRING_STAT_1 TRING_STAT_2 TRING_STAT_3 TRING_STAT_4 TRING_STAT_5 TRING_STAT_6 TRING_STAT_7 TRING_STAT_8 699 soc_write During the establishment direct use of soc_write would cause a signifi
25. c 74KB C source file C INCLUDE a smtp c 33KB C source file 3 SOURCE a socket c 134KB C source file ETHER a timeout c 13KB C source file C Startup X mia e ama H Figure 5 1 Folder Structure of the emBetter Protocol Suite 5 2 2 Module Structure The implementations of the TCP IP software suite often referred to as TCP IP stack results in a complex code structure Abstraction helps to create different compilation units that represents the functionality of a of the TCP IP stack A compilation unit comprises a set of functions and option settings and is referred to as module C does not especially support modular principles but provides the possibility to create several compilation units within one software project Since the internet protocol suite is designed as layer model the modules in emBetter are designed relating to the specific layers As shown in Table 6 3 drv_modem c Functions some layers are consolidated in one module However the general idea of having one layer being dependent on the other is reflected in the modules Each module depends on services of another module and provides functionality to one or multiple module as discussed in 3 3 2 Communication Flow It follows a top down strategy which means that the services are defined in the lower layer s header file that is included by an upper layer The Designer Reference Manual DRM049 Rev 0 50 Overall Implementation of emBetter MOTOROLA For More informat
26. code with a start and an end tag temp value lt hc12 status a C start tag ra x end tag dynamic function function parameter Figure 6 18 Dynamic Content in an HTML Page Between the two tags any name for a function is allowed But for finding out quickly the required function the names should not be too long or similar Names are mapped to functions by two variables dyn_func_names holding zero terminated strings and pdyn_func consisting of function pointers of the type UINTS8 pDynFunc UINT8 cSock UINT8 pStartTag UINT16 pDynFuncSent The mapping of function names to functions is similar to the mapping of file names to file constants Function names are set in the string Designer Reference Manual DRM049 Rev 0 100 Layer Implementation of emBetter For More Information On This Product Go to www freescale com MOTOROLA Freescale Semiconductor Inc Layer Implementation of emBetter Handling of Web Pages dyn_func_names and must be at the same position as the corresponding function that has to be executed defined with a function pointer in pdyn_ func Example const UINTS dyn_func_names HTTP_DYNFUNC_NUM DYN_FUNCTION_POINTER pdyn_func HTTP_DYNFUNC_NUM UINTS8 status same spit UINTS PportA_hex rT attp_dy UINTS nai 7 positions pa f names not necessarily i function names differ very identical much Figure 6 19 HTTP Functions for Dynamic Content If the
27. defined version the emBetter protocol suite shows extremely small code and memory size at a reasonable performance 1 6 Market positioning DRM049 Rev 0 In order to push its availability in the market emBetter is distributed as an open source product However this applies only for the application in the alarm control panel reference design ACPRD For additional features and integration of customer s application support is performed by Steinbeis Transfer Centre for Embedded Design and Networking STZEDN w3 a Design Alliance Partner of Motorola Inc Designer Reference Manual MOTOROLA emBetter A Short Overview 17 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc emBetter A Short Overview Designer Reference Manual DRM049 Rev 0 18 emBetter A Short Overview MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Section 2 Connecting Embedded Applications to the Internet 2 1 Status and Trends Remote maintenance and control is already widely used in industrial automation and building automation and gains acceptance for many other applications for example smart home appliances consumer electronics networking devices Internet and web based connectivity is playing a major part in unifying network infrastructure and company information flow It i
28. h 2616 Mail alerter smtp c Implementation of a SMTP client according to RFC 821 and RFC 822 smtp h 5 Internet socket c Includes the implementation of the protocols needed for internet 2 Protocols socket h communications 5 e P according to RFC 791 e ICMP according to 792 g e UDP according to RFC 768 e TCP according to RFC 793 Designer Reference Manual DRM049 Rev 0 52 Overall Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Structure and Interfaces Table 5 1 List of Compilation Units DRM049 Rev 0 Module Files Description PPP ppp c Implementation of the Point to Point Protocol according to RFC 1661 a ppp h and RFC 1662 T ke Physical physical c Provides basic network interface functionality Includes modem physical h handling and serial communication g Modem drv_modem c Routines to open and close a modem connection Modem commands pa drv_modem h that are specific to a particular type are defined in set_modem h This set_modem h allows to adopt the modem driver easily to other modems Hardware sci_12 h Hardware abstraction layer Provides a function that initializes serial sci_12 c communication interfaces input and output ports a Timers timeout c Provides functions for timing purposes One hardware timer is being S timeout
29. h used to dynamically start and stop software timers 2 Debug debug c Provides functions for debug information output In this implementation interface debug h debug information are sent to a serial interface Out buffer buffer c Logical out buffer management utility functions gt buffer h ifndef _ DECL_PPP_H define DECL PPP H extern tendif tdefine _ DECI _PPP_H a include PPP h DECL_PPP_H__ UINT8 cPPP_readState Figure 5 3 Declaration of API Variables The function prototypes for local functions can be found at the beginning of the code module whereas function prototypes forming a software interface are defined in the associated header file Software interfaces are used in emBetter to implement the two important boundaries in the TCP IP model 2 High level protocol address boundary is called Data link interface and the operating system boundary is called Socket interface On the high level protocol address boundary datagrams and IP addresses are passed on the operating Designer Reference Manual MOTOROLA Overall Implementation of emBetter 53 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter system boundary an application program interacts with an interface of the TCP IP stack that is considered part of the operating system interface names protocols conceptual layer a A a S 2 Application I N L A A
30. hosts possible 2 3 3 Gateway based Connectivity Via Internet 2 3 3 1 Overview Internet connectivity using a gateway for the connection is very suitable for smaller devices because a part of the functionality can be extended to this more powerful computer Doing so allows the step by step implementation of the necessary protocols on the embedded device up to the final release There are two possibilities for internal networking either P conformant or other protocols 2 3 3 2 Internal use of internet protocols Designer Reference Manual The use of TCP IP protocols on the microcontroller side allows for highest flexibility and portability However additional protocol overhead in the microcontroller is required In most cases Ethernet is used as layer 2 protocol because its interworking with TCP IP is proven for example ARP and because frame sizes show a good match Nevertheless the use of other protocols such as CAN for industrial automation or LIN for home and facility automation is well possible DRM049 Rev 0 24 Connecting Embedded Applications to the Internet MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Internet Connectivity Configuring uC uC uC Gateway Internet Computer Bus CAN LIN PC y Ethemnet SS Lad z Figure 2 3 Gateway based Connectivity with
31. is established This preserves the application from implementing a further state machine to open or close the socket connection SMTP_Write is called periodically and gives a negative response as long as the e mail is not transmitted successfully In order not to block the microcontroller the communication is realized in a multistage state machine mapped in Figure 6 22 Non blocking Implementation of SMTP This finite automaton is separated into three state machines of which the first one SMTP_STAT_ shows the general DRM049 Rev 0 104 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Simple Mail Transfer Protocol communication state of the SMTP client The second one represents the receive states for the reply message from the server and the third one shows the particular position in the string to be transmitted This is done because the outgoing strings are not combined before sending but they are sent as separate messages over the communication channel SMTP_STAT_ _ Receive Open Communication stack Communication established WAIT Reset attempt counter Create socket socket successfully created Connect socket to SMTP server Socket connected Receive 5xx Axx Receive 220 CONN2 Send HELO lt host IP
32. is possible in multiple ways The two most important are the following Designer Reference Manual Predefined IP addresses are possible for debugging purpose and if the protocol stack is only to be contacted by a known directly connected host This case is shown on the left hand side of Figure 6 7 Negotiation of IP Addresses with LCPC If the microcontroller shall retrieve its IP address from an Internet Service Provider the right hand side of Figure 6 7 Negotiation of IP Addresses with LCPC has to be used Here the requesting host asks for a valid address with an empty REQ packet The ISP assigns an address from his IP address pool The client sends a further request with his new IP address that is acknowledged by a final ACK packet For the rest of this session the client is now addressable through the internet by the assigned address If remote hosts are allowed to connect to the microcontroller if ALLOW DIAL IN is enabled the negotiation of the addresses is prone to errors because in many cases the IP address settings of the dial in computer are special and the errors difficult to find The negotiation is processed depending on the settings of the remote host here a few cases If the remote host wants to retrieve an IP address the protocol stack assigns an address to it If the host asks to have its fix address negotiated the stack tries to retrieve an address from this host as if it was an ISP as maybe the host is con
33. of setting a project global error variable brings more flexibility to further enhancements than coding the error code in the return value of the function DRM049 Rev 0 Designer Reference Manual MOTOROLA Overall Implementation of emBetter 55 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Figure 5 6 Example for Exception Handling shows an example of the function soc_read and how an exception handling can be realized soc_read returns the length of data read and sets the project global variable net_errno according to its result UINT16 iNumBytes iNumBytes soc_read cSock amp Buffer NUM_BYTES socket read call returns the number of bytes read if iNumBytes gt 0 everything OK bytes were read else switch net_errno return value of 0 means an error occurred case ERR_SOC_BADF exception handling goes here break case ERR_SOC_NOTCONN break case ERR_SOC_CONNRESET break case ERR_SOC_AGAIN break Figure 5 6 Example for Exception Handling As further parallel sockets are available the global variable net_errno is not sufficient for handling all errors that may occur when writing to a socket Therefore the struct soc_errno is introduced It represents the current error state of the single sockets The error codes of this struct are the same as for the net_errno variable By this approach paral
34. sockets or e soc socket e soc _ connect in case of TCP client sockets The structure sockaddr presents as following Designer Reference Manual MOTOROLA Layer Implementation of emBetter 85 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter struct sockaddr UINT32 daddr IP address of the connected peer UINT16 dport destination port number UINT16 num local port number Figure 6 10 Design of a sockaddr Struct A socket can easily be accessed using its array index Since a socket represents for TCP level a connection and for UDP a communication end point the destination IP address and port number and the local port number uniquely define it as the client chooses for every new connection to a known port for example port 80 for www a random or succeeding port number A socket is considered unused when the variable cState is set to STA SOC _FREE 6 6 3 Incoming Data After IP evaluated the values of the header of the incoming datagram the function soc_handler processes both UDP and TCP datagrams In both cases it is only possible to call the specific protocol handler if there is an existing socket to which the data can be assigned To identify this socket source IP address source port and destination port are compared with the port numbers and destination address of all active sockets with
35. the IP address of the microcontroller As a result the round trip time can be analyzed on the administrating PC Modem activity can be checked with LEDs ICMP packets are directly processed and answered in the IP layer see Figure 1 1 emBetter Protocol Suite Therefore multiple echo requests are likely to block a system To avoid this two countermeasures are offered e ICMP requests with data length bigger than ICMP_MAX DATALEN from socket hare simply discarded This should be sufficient for most cases because attackers usually use large packets in order to block a system e However to achieve maximum security against a ICMP based denial of service attack the ICMP functionality in netGlobal h can be switched off completely by setting PROT_ICMP to FALSE 6 6 Socket Interface 6 6 1 Overview DRM049 Rev 0 The classical socket API calls were defined as operating system APIs for high capacity computers Thus the following restrictions had to be Designer Reference Manual MOTOROLA Layer Implementation of emBetter 83 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter applied in order to keep code and data size small and to be able to include it into a non OS application e Exclusively non blocking function calls e No queuing of connection requests e Data transmit size at each soc_write call is limited to the maximum transmit unit o
36. this occurrence e the IP address transmitter It offers a service that allows dealing with an IP address dynamically assigned by the ISP After connecting to the Internet due to an incoming call or another event like a certain Port level or timeout the emBetter stack sends an e mail containing a hyperlink to its current address Depending on the recipient s mailbox and cell phone this might be a short message as well These are two provisional functions that have to be adapted or exchanged for new applications However all basic ideas for using SMTP for embedded devices are covered 6 9 3 Basic Functionality of the Code As the SMTP protocol is string orientated the data stream is be parsed for the beginning of the expected answer string received from the server Having found this character the program reads the following characters until the end of the expected string After this the socket data buffer is released and the next string from the remote host can be stored at the starting address of this buffer This helps to make the conversation more efficient As there is only one positive response for every state of the implemented mail transmission only the first number of an incoming string is evaluated 6 9 4 Sending an e mail A standard conversation between the implemented mail client and a SMTP server is shown in Figure 6 21 SMTP Communication Between Mail Client and Mail Server DRM049 Rev 0 Designer Reference Ma
37. 1 emBetter Protocol Suite cee ee 16 2 1 Architectures of Internet Connectivity 22 2 2 Direct Connectivity ste cca cadierccee deer biwecadeerees 22 2 3 Gateway based Connectivity with Internal Use of Internet PONG cade send ntwtan dene cde du od teee nee 25 2 4 Gateway based Connectivity with Internal Use of Non internet Fe eh eh ee 27 2 5 Dialup to an Internet Service Provider 28 2 6 Communication Initiation of the enBETTER Implementation 28 2 7 ISP based Connectivity with a Portal Server 29 3 1 ISO OSI Communication Layer Protocol 35 3 2 ISO OSI Reference Model and TCP IP Reference Model and Pe hho eS ee 36 3 3 HTTP Packets Via a Serial Link Takes 51 Bytes Plus a Variable PUP EIE onto ob oh Crea eRe th OER E ORS 37 3 4 The Information Flow in the Layered Model 9 38 3 5 Client Server Model ois ciscccsasesevwiar ss vacdesarces 39 3 6 Ports and Sockets for Concurrent Servers 40 4 1 Management of Output Buffers 005 44 4 2 Processing of Received Data Link Layer Packet 47 5 1 Folder Structure of the emBetter Protocol Suite 50 5 2 The Project Structure of the emBetter Protocol Suite 51 5 3 Declaration of API Variables 00005 53 5 4 Main Software Interfaces 0 0 0 cee eee eee 54 5 5 Main Software Interfaces 0 0000 eee 55 5 6 Example for Except
38. 2 Internet Section 3 Section 4 Section 5 Section 6 Section 7 Section 8 List of Sections emBetter A Short Overview 15 Connecting Embedded Applications to the ee ee eee ee E ee ee Tere ern 19 Basics of Implementation 33 Design Techniques for emBetter 43 Overall Implementation of emBetter 49 Layer Implementation of emBetter 63 Test environment 2 00 cece eens 109 SOCOS 1404444eee eha 119 Designer Reference Manual MOTOROLA List of Sections 5 For More information On This Product Go to www freescale com Freescale Semiconductor Inc List of Sections Designer Reference Manual DRM049 Rev 0 6 List of Sections MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 DRM049 Rev 0 1 1 1 2 1 3 1 4 1 5 1 6 Table of Contents Section 1 emBetter A Short Overview Protocol SUNG cn chica doors nade dade DRAERS 15 Tatget PIS oak bs ra eee eee a a ales 16 FORADIHY cocep 0858 oa eaeeneeedniaeeetn dae egeceedaws 16 MOWA we heat iat urd ed eee eae ew ete 17 OIE ATAS EEEE EEA T E OEE ETT 17 Market positioning o ecca cccccrenererr arana eae d ninia 17 Section 2 Connecting Embedded Applications to the Al 22 2 3 3 1 3 2 3 3 3 4 3 5 4 1 Internet Status and Trends usune eanna aa 19 System Design rscs
39. 3 The Point to Point Protocol PPP scsiscs see ceevedee cas 72 The Internet Protocol IP cc cawiveseccde see e eeu ewes 80 The Internet Control Message Protocol ICMP 83 Socket Interface 26s iced eh ORR meee Se eee ORE EA 83 Hypertext Transfer Protocol 5 01642 c0dsaddarecrnevaccdes 96 Handling of Web Pages csc ee nee eden eakae en 100 Simple Mail Transfer Protocol 20000005 102 UDP Applications 66 660 oe 8 AHR RRE RAD Ee Sed ORR 106 Section 7 Test environment Alarm Control Panel Reference Design 109 Setup of the Demonstration and Development Environment 109 DRM049 Rev 0 8 Table of Contents MOTOROLA For More Information On This Product Go to www freescale com DRM049 Rev 0 Freescale Semiconductor Inc Table of Contents 7 3 Simulation environment 0 0200 ee eee 112 Section 8 Sources 8 1 Web Resources 2 takne EEEN ee eee 119 8 2 ECA n aGre de oA ie eee OE OL dR ee ees 120 Designer Reference Manual MOTOROLA Table of Contents 9 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Table of Contents Designer Reference Manual DRM049 Rev 0 10 Table of Contents MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 DRM049 Rev 0 List of Figures Figure Title Page 1
40. 3 3 2 Communication Flow 3 3 2 1 Vertical Communication in the Protocol stack A layer is implemented to provide a service to the next upper layer These services are located at Service Access Points SAP which are known by the protocols using this interface The data which are sent or received at an interface are sent as Interface Data Units IDU that contains Interface Control Information ICI as well as Service Data Units SDU The SDU builds the data unit for the concerned layer on the target system and data that were given by upper layer protocols The ICI control the interface concerning data unit length and fragmentation As shown in Figure 3 4 The Information Flow in the Layered Model 9 this information is removed after the evaluation in the current layer whilst the SDU is transferred in the protocol stack The figure is to present the logical flows that occur on sending an application data stream from System B to System A using an Internet connection DRM049 Rev 0 Designer Reference Manual MOTOROLA Basics of Implementation 37 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation System A System B z Logical FI a Application Bata Stream gt Application A y p Transport e Seements A Transport Lr a S50 Network ePm a Network A y
41. 7 3 Implementation The data link interface provides the following functions that form the interface e ppp init e ppp_open Designer Reference Manual DRM049 Rev 0 78 Layer Implementation of emBetter MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter The Point to Point Protocol PPP e ppp_close e ppp write e ppp read These functions are described in detail in 6 3 6 PPP Functions and Global Variables In presence of a modem the function ppp_open initiates the calling of an internet service provider It returns immediately and repeated calling of the function ppp_open returns TRUE once the internet connection is established ppp_write expects as argument an out buffer handle This handle gives access to the different memory locations where parts of the packet are stored see Figure 4 1 Management of Output Buffers ppp_write sends a complete datagram over the serial interface and builds around the PPP header and trailer Upon reception of a datagram the function that is being called is the function passed on as an argument when calling ppp_init This is the event for the higher layer to notify incoming data ppp_read reads data sequentially out of the out buffer see Figure 6 8 Reading the PPPbuffer The arguments passed are a pointer to a memory space to write data to and the number of bytes to be read Int
42. Bundesamt Budget and equipment of households Federal www destatis de basis e evs budgtab2 htm 9 26 2003 http www vpi initiative com RFCs of IETF available at many sites for example http www ietf org rfc Crystal CS8900 Designer Reference Manual MOTOROLA Sources 119 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc w13 TLC Networks Plotted graphs on advertised window sizes 2001 8 2 Literature 1 2 3 4 5 6 7 8 Designer Reference Manual http tstat tlc polito it tsol main php 26 09 2003 Carlson J PPP DESIGN IMPLEMENTATION and DEBUGGING Addison Wesley 2000 ISBN 0 201 70053 0 Comer D Internetworking with TCP IP Vol 1 Principles Protocols and Architecture 4 Auflage Prentice Hall 2000 ISBN 0 13 018380 6 Kreidl H Kupris G Thamm O Microcontroller Design Hardware und Software Entwicklung mit dem 68HC12 HCS12 Carl Hanser Verlag Munchen Wien 2003 ISBN 3 446 21775 4 Kupris G Kreidl H Lill D Sikora A Implementierung von Internetdiensten auf einem Mikrocontroller am Beispiel eines HCS12 in einer Hausuberwachungszentrale embedded world 2003 Conference 18 20 2 2003 Nurnberg S 805 813 Kupris G Kreidl H Gutknecht N Lill D Braun N Implementation of a UDP IP User Datagram Protocol Internet Protocol Stack on HCS12 Mikrocontrollers
43. CP_SYN_RECV state Segment received Actions STA_TCP SYN SENT ACK verifies the acknowledgment number releases the associated buffer that holds the SYN segment sets socket in STA_TCP ESTABLISHED state Segment received ACK and SIN Actions verifies the acknowledgment number sends an acknowledgement segment with incremented sequence number sets socket in STA_TCP ESTABLISHED state DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 91 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter STA TCP ESTABLISHED Segment received Actions Segment received Actions STA_TCP CLOSE WAIT no flags verified verify if the segment contains data retrieve a st_buf element store incoming data send an acknowledgement segment for the received data by incrementing the acknowledgement number by the number of bytes received FIN send an acknowledgement to notify that the FIN segment arrived set socket in STA_TCP_ CLOSE WAIT state Segment received Actions STA_TCP LAST ACK ACK and FIN send an acknowledgement fin segment Segment received Actions STA_TCP FIN WAIT1 ACK Reset the socket Segment received Actions Designer Reference Manual ACK set socket in STA_TCP FIN WAIT2 state DRM049 Rev 0 92 Layer Implementation of emBetter MOTOROLA
44. Figure 6 11 UDP Data Storage shows how data is received and stored socket number struct sockaddr UDP data S csoc ipatten M st_buf cInBuf Figure 6 11 UDP Data Storage DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 87 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter As a result the maximum receive size for incoming UDP segments is defined as UDP_RX_ LEN SOC_BUF_LEN sizeof struct sockaddr The macro UDP_RX_LEN is defined in socket h 6 6 4 3 Sending UDP segments UDP does not occupy an out buffer element to store the outgoing data Therefore any data length can be accepted that is not superior of the maximum data length of the network interface The network interface advertises its maximum transmit length with the macro PPP IP TX LEN An application can send UDP segments by calling the socket function soc_sento To send the UDP data the following function calls are issued soc_sento gt udp_write ip_buildHeader buf_write Ppp_write Figure 6 12 Function Calls To When Sending UDP Datagrams In udp write a header is built on the stack since after transmission of the UDP segment any data can be discarded udp_write calls also the function to build the IP header since parts of the IP header can be used for the calculation of the pseudo header The followin
45. HTTP server finds the function name the function is being called as long the function returns HTTP_DYNS PROGRESS As soon as the function returns HTTP_DYNS_OKor the function name was not found the HTTP server continues to transmit data after the end tag If the function returns HTTP _DYNS_ ERROR the HTTP server closes the connection and returns in the state to accept a new connection A function that provides dynamic content receives three function parameters e cSock the socket of the HTTP server that this function can use to send TCP segments e pStartTag a pointer to the start of the function name This permits the dynamic function to exploit the values following the function name as function parameters e pDynFuncSent a pointer to a static variable that permits the function to statically store data for example its state or the amount of data sent This is necessary when the function generates content that requires the sending of more than one TCP segment A template of a function generating dynamic content presents as follows DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 101 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter UINTS dyn_template UINT8 cSock UINTS pStartTag UINT16 pDynFuncSent i UINTS cData DATA_LEN lt 4 data buffer for dynamic content UINTS cReturn functional
46. Internal Use of Internet Protocols The gateway itself may be PC with routing software a fully fledged stand alone router or another embedded device implementing a routing engine However the internal use of internet protocols comes with two flavors e If the gateway is just doing the routing the IP addresses of the microcontrollers are visible from the public internet Thus embedded web servers may easily be run However the devices are prone to attacks from the internet e Inthe second case the gateway is a router who runs Network Address Translation NAT or IP masquerading In most implementations NAT works only for clients behind the gateway Then no servers may be accessible from the outside However this is not a matter of principle P masquerading may saves costly internet addresses and leverage security as it is only the gateway s IP address which is visible in the public internet DRM049 Rev 0 Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 25 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Table 2 3 SWOT Analysis of Gateway based Connectivity With Internal Use of Internet Protocol and Ethernet Strength Weakness e Known Technology CS 8900 e Ethernet uncommon in home e Fast data transfer compared to appliances modem e Dependence on gateway sin
47. SP based Connectivity With Dialup 29 SWOT Analysis of ISP based Connectivity With a POH ONS cis ciceawrenec cede diawaaeedsognandeawe 30 BSD Socket Function Implementation in emBetter 46 List of Compilation UNG sits tsk eed sade eae eee ea dank 52 Overview of Buffer Variables 200000005 57 Overview of Functions in buffer c 00055 59 Header and Data Location for the Different Protocols 60 S12 See FONCIONS 605 26 ce ce Selb woe ered eeeeeeeeehaes 69 CNVSIeLG FUNCIONS ct idewekee eaea Nat dew ee ee ees 70 drv_modem c FUNGHONG 0 ica cee ceasesas eee enedaeens 71 PPP FUMON 44 084656 Ua ceded ebioded eka en daeedtaawe 77 Constant Values in IP Header 000000000 82 Header Fields Used for TCP Segment Processing 89 Socket Values for TCP and IP Header 94 Designer Reference Manual MOTOROLA List of Tables 13 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc ERMEE Designer Reference Manual DRM049 Rev 0 14 List of Tables MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Section 1 emBetter A Short Overview 1 1 Protocol Suite The emBetter protocol suite contains the following modules see Figure 1 1 emBetter Protocol Suite Application layer e HTTP web server also for d
48. TOROLA Test environment For More Information On This Product Go to www freescale com 115 Freescale Semiconductor Inc Test environment E Profiler STRING C E rtshel2 c acprd_main c E acprd_encoder c acprd_freqout c acprd_keyb c acprd_song c acprd_timer c acprd_vectors c DISPLAY C TIMEDATE C 12_EETS C 12_S8cI c 12_SPI C 12_ATD C E Buffer c E drv_modem c physical c E PPP c E SMTP c socket c HTTP c HTML C START12 C Figure 7 6 Profiler Window 7 3 3 4 Coverage The Coverage component see Figure 7 7 Code Coverage Information informs about the lines in the source code that have been executed Additionally to the Marks in the Source window showing which lines are not compiled at all this gives hints about programmed branches that have not been taken or functions not called up toa moment Designer Reference Manual DRM049 Rev 0 116 Test environment MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment Simulation environment 1 E Coverage STRING C i E rtshel2 c acprd_ main c 4 E acprd_encoder c H E acprd_freqout c acprd_keyb c acprd_song c acprd_timer c d E acprd_vectors c DISPLAY C i TIMEDATE C E 12_EETS C B s12_scrq c 12_sPr c E 12_aTD c E Buffer c E drv_m
49. acprd_main c Iof Xx HB File Edit View Search Project Debug ProcessorExpert Window Help l x Pea ERa T EEE E a e Bei void main void Initialization of user applications ifdef DBG_GEN_INFO dbg_init Debug information tendif if PROT_SMTP cResult smtp_init 7 initialize SMTP and lower layers tendif if PROT_HTTP cResult http_init initialize HTTP and lower layers tendif Application loop for User applications soc_entry Provide new data at socket ge ee tot hard stveni Timer for TCP retransmissions if PROT_SMTP MailCheck SMTP applications AdminCall endif if PROT_HTTP http_entry Check for HTTP contents to process tendif 5 5 5 5 5 5 2 2 _ WOMAD l fl Line 903 Col64 gt ZA Figure 5 5 Main Software Interfaces 5 3 Exception Handling Most of the time an exception occurs it cannot be handled within the function itself but has to be passed on to the calling function There are two basic principles used in emBetter for exception handling firstly returning an error code as function return value or secondly setting the project global variable net_errno to a specific value The values are defined as preprocessor defines in the corresponding header file The second option was chosen for functions with a return value In this case the method
50. al Port 1081 Connect Figure 6 23 Proprietary UDP Client Software DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 107 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Designer Reference Manual DRM049 Rev 0 108 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Section 7 Test environment 7 1 Alarm Control Panel Reference Design Together with Motorola application engineers Elektronikladen has developed a new alarm control panel reference design ACPRD which is based on a Motorola HCS12 microcontroller The panel can read in a jog dial input 4 push buttons or 3 inputs for current controlled circuits Outputs are realized for a sound module for sirens or lights and for alarms Bidirectional communication can be handled via an RS232 Interface as well as with an interface for CAN or LIN Buses The presented protocol suite emBetter realizes the communication with the Internet Therefore a socket modem SC336H1 from Multi Tech is built in which makes the Internet connectivity as easy as plugging the phone jack The 240 x 64 pixel LC display eases controlling and debugging 7 2 Setup of the Demonstration and Development Environment DRM049
51. allback functions are functions which are called with their memory address from the lower layer protocols Below the IP callback function in the PPP module is described The initialization of the PPP Module SINT8 ppp_init void CallbackIP UINT8 UINT8 cIPAddr requires two parameters e CallbackIP isthe function pointer of the callback function of the higher layer which is the function that has to be called when a valid IP packed is being received e cIPAddr is the pointer where the IP address is to be stored Data packets of a random length build the communication via Internet An internet node does not know in advance when it will receive a new data packet and how long this packet will be Thus at first hand the interrupt based processing seems to be the appropriate method of handling incoming data However due to the high complexity of processing internet protocol conformant data the main application of the microcontroller might be blocked for a too long time In order to keep interrupt service routines as short as possible the emBetter realization chooses a combined solution Only the individual bytes of a received packet are read in with an Interrupt Service Routine After having Designer Reference Manual MOTOROLA Design Techniques for emBetter 47 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Design Techniques for emBetter received a complete frame which i
52. arrier Detect DCD for the Modem On Socket Modem SC336H1 DTR PM3 DCD PM2 define DTR_OUTPUTDDRM amp 0b11111011 DDRM 0b00001000 define DTR_ONPTM amp 0b11110111 Reset port pin for DTR define DTR_OFFPTM 0b00001000 Set port pin for DTR define CD PTM amp 4 Returns true if CD is set BRR I RK IR FE KE IR TR FE KE TR TR FE KE TOR TOR TOR E E e TOR TOR TOR TOR TOR TO IOI k k k k k k f 6 3 The Point to Point Protocol PPP 6 3 1 Overview Designer Reference Manual In emBetter PPP is the interface between the interrupt driven data flow from the SCI and a packet oriented data transfer of the Internet protocol stack When the physical connection is established see 6 2 Modem Communication the interrupt service routine ISR_sci0 is directed to ppp_receive ppp receive scans the incoming data for the START flag other characters are discarded After START is perceived data is written into the buffer for incoming data PPPbuf fer until an END flag is found The START and END flags are not written into the DRM049 Rev 0 72 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter The Point to Point Protocol PPP buffer because they do not belong to PPP but the underlying HDLC After the END flag is found the state variable cPPPStatus is set to IS FRAME IS
53. cant overhead as each string is composed of static Designer Reference Manual MOTOROLA Layer Implementation of emBetter For More Information On This Product Go to www freescale com 105 Freescale Semiconductor Inc Layer Implementation of emBetter 6 9 7 Error Handling and dynamic contents for example RCPT TO lt recipient gt EOL Therefore smtp _send is called in the application smtp send collects the various string fragments until EOL is detected or the minimum number of bytes SMTP_MIN_LEN is reached As a result the number of TCP segments for a complete mail is MailDataLen SubjectLen TCP_TX_LEN TCP segments 8 In an e mail application the error handling is likely to be implemented depending on the strings received from the SMTP server If a 4 is received as first value the client is asked to wait before trying again to transmit the string On reception of a 5 the client stops the transmission In emBetter a flag is set in order to send a standard memo to the recipient defined as SMTP_REP_ADDR in the SMTP header file If the SMTP server has accepted the memo once all further error reports generated on the way to the final recipient are directed to the sender address 6 10 UDP Applications Designer Reference Manual Low cost microcontrollers or devices that are dimensioned for their principal application do usually not provide the performance and memory to additional
54. ch travel independently from source to destination is called packet switching e The modularity of a layered protocol stack sets high requirements on the efficient realization of each layer and the interfaces in between e The client server model implies an asymmetric communication flow with the overall capability of being reached for servers 3 2 Packet Switching DRM049 Rev 0 An important side of the Internet communication is the fact that the information does not travel in a continuous stream but in the form of small data packets A packet is an information unit whose source and destination are network layer entities A packet is composed of the network layer header and possibly a trailer and upper layer data The header and trailer contain control information intended for the network layer entity in the destination system Data from upper layer entities is encapsulated in the network layer and trailer The advantage of this packet technology is that every packet travels independently from the others This makes the whole information transfer resistant against transmission failures Also the system bandwidth is used very effectively Designer Reference Manual MOTOROLA Basics of Implementation 33 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation A disadvantage of this technology is the fact that control information has to be added to each and
55. cting Embedded Applications to the Internet and controlled by an application server The remote host connects to the application server which presents a user interface The dynamic data for this interface are retrieved from the embedded devices The use of a portal server gives highest flexibility best performance and highest portability Additionally it might be the basis for a VPl conformant architecture w10 All services between host computer and portal server and between portal server and embedded device should be run over HTTP Table 2 6 SWOT Analysis of ISP based Connectivity With a Portal Server Strength Weakness e Web services from the ISP e Microcontroller only online after ISP has to call back the microcontroller e Host authentication performable by portal e High availability through redundancy dialup e User interface on portal possible Opportunity Threat e Alert may be interpreted by portal e ISP might change dialup e Independent from remote host s e Dependence on portal server hardware and ISP if not properly designed 2 3 5 Conclusion The SWOT analyses in this chapter demonstrates that there is no ideal general internet connectivity for embedded devices The best solution strongly depends on the actual circumstances This makes it an important challenge for a TCP IP protocol suite such as emBetter to provide a set of module which can be adapted to a maximum number of use
56. ction all sockets with a valid reference to a st_buf element containing sent data are checked for retransmission timeouts The retransmission timeout is reached when the retransmission trigger value iTOend in the st_buf element see Figure 6 14 TCP Segment Stored in st_buf index cData is smaller than the value of the free running counter iTCP_ tmr Designer Reference Manual MOTOROLA Layer Implementation of emBetter 95 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter If the free running counter passed the value in iTOend the segment is resent by the function tcp write To limit the number of retransmissions the variable cTOretr is decremented by one every time a retransmission occurred After this value has reached zero it is assumed that the connected peer is not responding anymore and as a result the socket is being reset 6 6 5 5 Summary This TCP implementation covers only the basic features of the TCP specification The restrictions applied to the full TCP implementation No options allowed One out and one in buffer per socket Checksum verification beginning with version 1 2 Basic transitions of the TCP state machine implemented Urgent mode is not supported 6 7 Hypertext Transfer Protocol 6 7 1 Overview The emBetter HTTP server covers the following features Non blocking implementation Supports the HTTP methods GET and POST
57. ction name Description buf init Initializes the module buffer c DRM049 Rev 0 Designer Reference Manual MOTOROLA Overall Implementation of emBetter 59 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Table 5 3 Overview of Functions in buffer c Function name Description buf _getHandle Returns a handle and grants the right to call buffer functions with this handle buf_write A protocol calls this function to register the address and the length of its data in the buffer structure buf_getProtCnt Returns the number of protocols already registered in the buffer structure buf_access Returns the address to a buffer element from a specific protocol buf_clear Sets all buffers to the initial value buf_getTotLen Returns the sum of all the lengths registered in the buffer structure In order to write data one of the top level protocols like HTTP or SMTP TCP or UDP prepares the data and the header to send and then calls first the function buf _GetHand1le to retrieve the buffer handle Next it registers its data and header in the out buffer by calling buf Write Afterwards it calls the write function of the lower layer protocol and passes only the buffer handle All protocols having written their information into the struct PPP accesses the different memory sections by calling buf_Access and sends the pack
58. d in Figure 5 7 Call Structure of Function ppp_entry indicate protocol multiplexing To provide a highly compatible software interface the access to the frame stored in PPPbuf fer is provided through the function ppp_read This function allows copying a number of bytes to a specified memory address The buffer is read out sequentially Data that has been read by ppp_read cannot be read a second time However the internal functions of the ppp c module have direct access to the memory These are e ppp _handleLcP e ppp handlePAP e ppp _handleIPCP e ppp _rejectProtocol The function call structure cannot be interrupted by other processes therefore it is not necessary to protect the function ppp _read Designer Reference Manual DRM049 Rev 0 58 Overall Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com 5 4 3 Outgoing Data Freescale Semiconductor Inc Overall Implementation of emBetter Buffer Handling and Data Flow All function calls in the structure must not be blocking otherwise no new frames can be received upon an error The timing constraints during the ppp negotiation are relatively strict regarding the low performance of low cost microcontrollers Furthermore the packets of a request and the answer to send are very similar which allows building the outgoing packet directly in the PPP buffer to save calculating speed For the same reasons the f
59. d into different files At the top the module physical c and its header file Designer Reference Manual MOTOROLA Layer Implementation of emBetter 63 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter physical h present an abstraction layer for the PPP module It contains the API functions to handle the communication on the physical layer Changes in this module are only necessary if the way to connect to the Internet changes for example when using a null modem cable or an IrDA link The most important changes during the adaptation to the user environment are the integration into the user s Serial Communication Interface control structure and the implementation of new modem specific drivers In emBetter the SCI communication is realized with an interrupt driven application in s12_sci c In case that the second SCI is already used in the user s application the procedures for SCI control of Internet connectivity are preferentially to be implemented in the user s module In case that only on SCI is used only the prescalers in s12_sci h are to be set to match the transfer rate of the modem and the oscillator frequency The modem driver is realized in the drv_modem c module which in most cases has not to be modified To simplify the transfer to different modems the modem driver has two different header files drv_modem h contains the API function prot
60. d not the way data is stored In emBetter each module consists of a set of functions as well as module global variables Part of the functions and variables are intended to be used within the module whereas the rest are intended to be provided to other modules as software interface Global variables that are to be accessed by other modules are located in the module s header file By having each module include its own header file the consistence of variables is raised The example shown in Figure 5 3 Declaration of API Variables extracted from the PPP source and header files show the declaration of API variables Before including the header the declaration prefix here DECL PPP H _ is defined When building the project the preprocessor removes the prefix for the ppp c object file in all other objects the prefix is replaced by extern so that the variable is only created once But care must be taken that the prefix is only defined once in the project Table 5 1 List of Compilation Units Module Files Description Application main c This module holds the code of the application a task sharing loop to main h enable the network stack to operate and the initialization of the hardware through functions that are provided HTML project html c Holds constant variables that represent HTML pages 8 html h 2 Web server http c Implementation of a web server supporting HTTP 1 0 according to RFC http
61. delay Interrupts a connection modem_init UINT8 void tot_init pCBackPhy Initialization of the pCallit void modem_hangUp cModStatus clndex modem stores the modem_inpComp InitAns callback routine sci_setCallback pInpCompstr tot_delay clnpCompState modem_write InitSeq modem_inpComp void volatile UINT8 clnpCompState Compares strings clndex sent by the modem clnpCompWrong with the expected pInpCompStr answers modem_open UINT8 void modem_inpComp cModStatus Opens a connection sci_setCallback cDialAnsw to the ISP tot_doNothing pInpCompstr negotiates the tot_setTimeout clnpCompState connection modem_dial cDialTimeOut parameters with the tot_getStatus clnpCompWrong ISP s modem tot_resetTimeout modem_hangUp modem_receive void volatile UINT8 sci_sendChar ISR for incoming calls modem_write void const UINT8 sci_sendChar Sends a character cData via the SCI modem_close void void modem_hangUp cModStatus Interrupts a modem connection 6 2 7 Modem Initialization DRM049 Rev 0 Modem operation is controlled by AT and S register commands issued by the DTE ACP and with the signals DTR Data Terminal Ready and DCD respectively CD Data Carrier Detect On the ACP Alarm Control Panel DTR signal is connected to port M pin 3 PM3 and DCD is connected to port M pin 2 PM2 on the MC9S12DP256 microcontroller The DTR TTL Active Low input is turned ON low by the DTE when the DTE is rea
62. ductor Inc For More Information On This Product Go to www freescale com Freescale Semiconductor Inc HOW TO REACH US USA EUROPE LOCATIONS NOT LISTED Motorola Literature Distribution P O Box 5405 Denver Colorado 80217 1 303 675 2140 or 1 800 441 2447 JAPAN Motorola Japan Ltd SPS Technical Information Center 3 20 1 Minami Azabu Minato ku Tokyo 106 8573 Japan 81 3 3440 3569 ASIA PACIFIC Motorola Semiconductors H K Ltd Silicon Harbour Centre 2 Dai King Street Tai Po Industrial Estate Tai Po N T Hong Kong 852 26668334 TECHNICAL INFORMATION CENTER 1 800 521 6274 HOME PAGE http motorola com semiconductors Information in this document is provided solely to enable system and software implementers to use Motorola products There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Motorola reserves the right to make changes without further notice to any products herein Motorola makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Motorola assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability including without limitation consequential or incidental damages Typical parameters which may be provided in Motorola data sheet
63. dy to transmit or receive data DTR ON prepares the modem to be connected to the telephone line and maintains the connection established by the DTE manual answering or internally Designer Reference Manual MOTOROLA Layer Implementation of emBetter 71 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter automatic answering DTR OFF places the modem in the disconnect state under control of the AT amp Dn and AT amp Qn commands The effect of DTR ON and DTR OFF depends on the AT amp Dn and AT amp Qn commands Automatic answer is enabled when DTR is ON if the Answer Ringcount selectable option is not set to 0 Regardless of which device is driving DTR the modem will respond to an incoming ring by going off hook and beginning the handshake sequence The response of the modem to the DTR signal is very slow up to 10 ms to prevent noise from falsely causing the modem to disconnect from the telephone line When AT amp CO command is not in effect DCD TTL Active Low output is ON when a carrier is detected on the telephone line or OFF when carrier is not detected DCD can be strapped ON using AT amp CO command The macros to control DTR and DCD from the software are in S12_SCI H BRR I RK e RR IR AE E TR FE KE TR TR TCR A E TOR AE AE K TOR TOR TOR TOR TOR TOR TO IOI IO k k k kk f Data Terminal Ready Signal DTR for the Modem Data C
64. e Action Employer Motorola Inc 2003 DRM049 For More Information On This Product Go to www freescale com
65. e Manual MOTOROLA Layer Implementation of emBetter 77 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter 6 3 7 The Data Link Interface 6 3 7 1 Introduction The data link interface forms the interface between the internet layer and the data link layer as described in 5 2 3 Software Interfaces This interface should give access to different types of hardware drivers Besides point to point connections a common way to connect to the internet is Ethernet For Ethernet connectivity the Crystal CS8900 Ethernet controller 12 is envisaged as it is particularly suitable for low cost Ethernet connectivity in terms of availability costs and feature set The interface consists of a routine that sequentially reads out a buffer containing a complete frame e Incase of modem communication this buffer is pppbuffer on the microcontroller e Incase of Ethernet based communication this buffer with a complete Ethernet frame is on the external Ethernet controller 6 3 7 2 Specification In consideration of the facts mentioned above the interface was defined the way that e The data link layer provides a function to read data of incoming segments sequentially No direct memory access to the buffer is provided e Outgoing data is passed to the data link layer when a complete segment is ready to transmit e Incoming segments are notified through an event 6 3
66. e attempt to transmit too long data packets must result in an exception This implementation supports only one connected interface and therefore routing and gateway functionality is not required This leads to major savings in terms of performance and memory usage e No memory necessary for collecting fragments e No forwarding of IP datagrams DRM049 Rev 0 82 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter The Internet Control Message Protocol ICMP e For performance reasons the header checksum of incoming datagrams is not verified and assumed to be correct In a statistic 8 done on an Ethernet network shows that as little as 14 out of 170 10 transmitted IP datagrams had a corrupt header That is a probability of lt 0 01 and therefore the time consuming checking of the checksum is being left out For version 1 2 IP header checksum verification will be included 6 5 The Internet Control Message Protocol ICMP emBetter implements a basic version of ICMP As microcontrollers mostly do not possess a user interface the protocol stack is not intended to send echo requests to remote hosts However the echo reply function can be very useful for debugging purpose or for inspecting if the stored IP address for the microcontroller is right To do so the administrator sends a PING request to
67. ed to the clock of the evaluation board M68EVB912DP256 Designer Reference Manual DRM049 Rev 0 110 Test environment MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment Setup of the Demonstration and Development Environment e Allinterrupt vectors of the MC9S12DP256 have to be pointed toa fix jumping table in RAM so that the software could be loaded into RAM and the Flash ROM need to be programmed only once e All modem settings and commands have to be adjusted to the Zyxel standard w8 On the ACP reference design board the modem is already on the board It is a socket modem SC336H1 from Multi Tech The socket modem is connected to the SCI1 of the MC9S12DP256 Port M pin 3 PM3 is used as output for DTR and port M pin 2 is used as input for DCD For debugging purposes debug messages were extensively included in the source code An example is shown in Figure 7 2 Information Provided on Debug Interface However on the ACPRD SCI1 is connected to a LIN transceiver and is therefore not available for a debug interface HCS12_Debug HyperTerminal or Datei Bearbeiten Ansicht Anruf bertragung ole ala cls PPP packets received 7 sent 9 z PPP packets received 8 sent 9 IPCP IP set to 10 20 5 7 IP Datagram receivedIP Datagram length 29 IP Datagram length 33 IP Prot ID 17 P UDP packet received Application UDP packet with data length
68. ernally ppp_read keeps track of a pointer copies the amount of data and moves the internal pointer for the number of bytes read This allows to sequentially read the PPP buffer DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 79 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter void func void PPP_Read amp Datal 2 PPP_Read amp Data2 8 PPP_Read amp Data3 4 Figure 6 8 Reading the PPPbuffer If there are more bytes requested then found in the buffer ppp_read returns only the number of bytes read If the pointer to the memory space is a null pointer then no data is copied only the internal counter is incremented for the number of bytes specified 6 4 The Internet Protocol IP 6 4 1 Overview The Internet Protocol is the major protocol to interconnect networks It is the dominant layer 3 protocol and provides the platform for ubiquitous computing Its implementation efficient may be very efficient as it offers connectionless and unreliable communication Designer Reference Manual DRM049 Rev 0 80 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter The Internet Protocol IP 6 4 2 Incoming Datagrams 6 4 3 Outgoing Data DRM049 Re
69. ese headers are standardized one should not search alternative solutions Additionally in most PC oriented protocol stacks one layer calls the next layer via a function call The parameters of this function include the data to be transmitted This implies copying the variables for most protocol stacks which increases processing time and memory space However a more sophisticated approach is possibly in dedicated solutions In the implementation of emBetter the out buffers are managed ina central buffer module Figure 4 1 Management of Output Buffers DRM049 Rev 0 Designer Reference Manual MOTOROLA Design Techniques for emBetter 43 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Design Techniques for emBetter Designer Reference Manual Protokolle Buffer Data soc ie TCP tos IP betel PPP y 3 8 PPP IP TCP Data PPP Sa O o Zlo alo aloalo Cial oual Da Dla DaD v e S LeeLee SCI I 22 22 22 Figure 4 1 Management of Output Buffers In order to generate an outgoing buffer the highest layer protocol requests an output buffer If there is an output buffer available it gets back the handle for this buffer If there is no buffer available at the time of the request because all existing buffers are containing data still to be t
70. et over the physical interface This concept allows the different protocols to store their data in a freely chosen address space Table 5 4 Header and Data Location for the Different Protocols lists the different protocols and where each protocol stores its data and header to send Table 5 4 Header and Data Location for the Different Protocols Protocol Description TCP Header and data are copied to an st_ buf element UDP The data location is advertised by the application through a pointer UDP builds its header on the stack IP The header is stored in the module global variable stIP_ out_header Designer Reference Manual DRM049 Rev 0 60 Overall Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Buffer Handling and Data Flow Table 5 4 Header and Data Location for the Different Protocols Protocol Description PPP The header is created on the stack ICMP Data and header are put on the stack DRM049 Rev 0 Designer Reference Manual MOTOROLA Overall Implementation of emBetter 61 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Designer Reference Manual DRM049 Rev 0 62 Overall Implementation of emBetter MOTOROLA For More Information On This Product Go to
71. etter socket API socket soc_socket open soc_open connect soc_connect bind soc_bind close soc _close listen soc_listen accept soc_accept write soc _write read soc_read sento soc_sento recv trom soc_recvfrom 4 5 Callback Functions When a station receives a valid packet on the data link layer it is not yet clear which upper protocols have to process this packet This is defined within the packet on each layer A protocol or type field carries the encoded information which is the next protocol to be called Figure 4 2 Processing of Received Data Link Layer Packet gives an Ethernet based example Designer Reference Manual DRM049 Rev 0 46 Design Techniques for emBetter For More Information On This Product Go to www freescale com MOTOROLA 4 6 Blocking DRM049 Rev 0 Freescale Semiconductor Inc Design Techniques for emBetter Blocking HTTP Ethernet destination addres _00 90 96 1D E9 99 Eere protocol type EEEN EEOAE ONE EE gt 0800 i inati gt 192 168 1 5 i Megosunaton andes en eee gt IP header protocol i TCP destination port number gt i TCP header data e g of application layer Figure 4 2 Processing of Received Data Link Layer Packet The upper layer protocols are called via callback functions C
72. every packet Together with the layered protocol stack being described below each protocol layer adds information to the data packet Therefore it is not very efficient to submit just a small piece of information because the overhead generated by the various protocols can be much larger than the transmitted data itself 3 3 Layered Protocol Models 3 3 1 The OSI ISO Reference Model and the TCP IP Implementation The Internet is a collection of individual networks connected by intermediate networking devices that functions as a single large network The challenge when connecting various systems is to support communication between disparate technologies Different sites for example may use different types of media or they might operate at varying speeds A network management must provide centralized support and troubleshooting capabilities Configuration security performance and other issues must be adequately addressed for the inter network to function smoothly The Open Systems Interconnect OSI reference model which was introduced in the seventies and released 1984 describes how information from a software application in one node moves through a network medium to a software application in another node Figure 3 1 ISO OSI Communication Layer Protocol Designer Reference Manual DRM049 Rev 0 34 Basics of Implementation MOTOROLA For More information On This Product Go to www freescale com Freescale Semiconductor Inc
73. f a TCP TCP_TX_ LEN segment or UDP datagram UDP_TX_ LEN e Limited number of sockets defined by SOC_NUM_ SOCKS in netGlobal h As emBetter socket API is a user interface each function call provides a designated exception handling All function calls result in a valid function return value Or TRUE and the global variable soc_ errno socket number is set to ERR_SOC_OK In case of an error the return value might be invalid or set to FALSE and the variable soc_errno socket number is set to the corresponding error This allows the calling function to handle exceptions differently As mentioned above emBetter is implemented as non blocking code Therefore it is a widespread error source that functions are not ready to accept new data when there might be still data in the out buffer waiting to be acknowledged In this case the function returns 0 as an indication that no bytes were transmitted yet The error variable is set to ERR_SOC_UNACK to indicate that there are still data in the socket s buffer and that this function has to be called again in order to transmit new data 6 6 2 Socket Management emBetter implements a simple socket API Basically a socket is defined by a number that refers to a socket element in the array stSocket SOC_NUM_SOCKS The constant Soc_NUM_ SOCKS indicates the number of sockets allowed and can be set in socket h Increasing the number of sockets results in a higher demand of RAM as one socket occupies
74. f emBetter For More Information On This Product Go to www freescale com 65 Freescale Semiconductor Inc Layer Implementation of emBetter Designer Reference Manual modem communication is changed from the known two state machine command and data mode into the version outlined in Figure 6 3 The Modem State Machine The software sends strings to the modem via the serial communication interface The answers are evaluated by interrupt service routines that control the transitions between the modem states Carrier Loss MOD_DATA DTR OFF Figure 6 3 The Modem State Machine The interrupt service routines depend on the state of the modem Incoming characters are always examined by Modem_InpComp The possible answer strings from the modem are stored in the EEPROM before emBetter at programming time Before setting the ISR to Modem_InpComp via SCI_SetCallback the pointer pInpCompStr is directed to the answer string in the EEPROM which is expected from the modem When an incoming character causes an interrupt the function Modem_InpComp compares it with the character at pInpCompStr Ifthe conditions are met the state variable cInpCompState is changed Figure 6 4 The States for Modem Input Comparison shows the possible values of this variable First Character matches Ch itch AND IMPCMP_REQ NPCMP_START ne sting C First char does not match Chars match not End of string Figure 6 4 T
75. figure to accept only a certain range of IP addresses If this does not work a default address calculated via an offset from the remote host s address is negotiated DRM049 Rev 0 76 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc A B A B RE R Da P0000 ack 10 2052 nak 19218 552 052 REQ 19 REQ 10 2 p85 2 ACK 10 20 52 ACK 192 168 55 2 Layer Implementation of emBetter The Point to Point Protocol PPP Figure 6 7 Negotiation of IP Addresses with LCPC The negotiation of compression options is not implemented because of the low gain of transmission speed in comparison to a high amount of additional computing 6 3 6 PPP Functions and Global Variables Table 6 4 PPP Functions Return value Function name Parameters Description for details see function header in C file SBYTE ppp_init void CallbackIP BYTE Initialize PPP BYTE clPAddr Call Phy_Init SBYTE ppp_open None Check Phy_Open Open PPP Void ppp_close None Close Phy layer Close PPP Void ppp_write BYTE cData Create PPP Header WORD len Send Packet WORD ppp_read None Deliver 16bit of data Set buffer ready to receive new packets WORD PPP InBuf_CpyFrom BYTE pData Copy a sequence of data to destination WORD uiLength Void ppp_entry None Check for new packets Direct packets to layers DRM049 Rev 0 Designer Referenc
76. folder should be copied into this structure When building the project using Processor Expert the sources can also be placed in the CODE folder as well as Processor Expert generates all user modules in this folder When using Processor Expert for the generation of hardware control functions care should be taken that the system files are not modified by the user Else a new generation of these files might destroy the changes Figure 5 1 Folder Structure of the emBetter Protocol Suite shows the file structure of the Alarm Control Panel Reference Design designed like a common CodeWarrior project DRM049 Rev 0 Designer Reference Manual MOTOROLA Overall Implementation of emBetter 49 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter N Explorer SOURCE Jof x Datei Bearbeiten Ansicht Wechselnzu Favoriten Extras See Ter Typ 12KB C source file one 7 KB C source file a drv_hw c 41KB C source file Ordner x B C emBetter 2 Documentation 3 SourceCode C BIN ja drv_modem c 24KB C source file CMD a ether c 42KB C source file 41 29 emBETTER Data ia html c 19KB C source file C PRM j a http c 88KB C source file 3 C Sources a ip_sec c 12KB C source file C ACPRD a physical c 11KB C source file EMBETTER a ppp
77. fter the initialization When a remote client tries to connect to the embedded device the two modems start negotiating the communication parameters for example concerning error control or communication speed After the correct settings are found the modem sends a 1 string to the microcontroller to notify that the carrier is established Until that moment of time the microcontroller is not in charge with the negotiation of communication parameters which gives performance to other applications Modem_receive calls the upper layer s callback function to inform that a connection is now active and that the incoming data are to be examined and answered by the upper layers 6 2 5 3 Remote activated mode This case see Figure 2 6 Communication Initiation of the emBETTER Implementation contradicts the strict layered model see 3 3 Layered Protocol Models However it allows a very cost effective implementation of the Internet communication When the REMOTE ACTIVE directive is enabled the microcontroller listens for incoming calls after the initialization When a call is received the connection is instantly interrupted and the global flag bConnect in netGlobal h is set This flag must be polled by the main application As soon as bConnect S TRUE the application opens a new connection via the ISP Designer Reference Manual DRM049 Rev 0 68 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go t
78. g fields are directly accessed to compute the checksum of the IP header e Source IP address e Destination IP address e Protocol number Designer Reference Manual DRM049 Rev 0 88 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Socket Interface e Length of the UDP segment After successful completion of ppp write the function returns to back to the application 6 6 5 Transport Control Protocol 6 6 5 1 Overview The TCP protocol is implemented in socket c and provides connection oriented reliable data transmission The complexity of this protocol requires normally significant resources therefore this implementation tries to meet the most basic requirements of this protocol in order to keep the demand for resources such as ROM RAM and CPU time low The socket API uses TCP and assigns a socket to a TCP connection Therefore any TCP actions are based on a member in the array of sockets stSocket defined in socket c 6 6 5 2 Receiving TCP segments DRM049 Rev 0 Upon receipt of a TCP segment the function tcp handler is called This handler needs to distinguish between different segment types and operations on the specified socket are issued The flags set distinguish the type of the segment In a first step the values out of the TCP header see Table 6 6 Header Fields Used for TCP
79. ging the internet connectivity 7 3 2 Settings for the emBetter on the Full Chip Simulation Target Designer Reference Manual Running an Internet protocol suite on a simulator does not seem to make much sense as nobody will have the time to simulate the whole Internet with its services and transmission errors on his computer Therefore the simulated microcontroller is to be connected to one of the computer s interfaces in order to communicate with real internet devices In the CodeWarrior s simulator debugger for HC S 08 and HC S 12 microcontrollers the Terminal component does this by redirecting the simulated microcontroller s Serial Communication Interface to the computer UART see Figure 7 3 Settings for the Terminal The external modem connected to the selected UART establishes a connection between the simulated microcontroller and the internet To make the system work properly a few points are important e The terminal has to be open with the Use Serial Port and Redirect simulator SCIO options selected Figure 7 3 Settings for the Terminal DRM049 Rev 0 112 Test environment MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment Simulation environment e The SCI for the modem connection must be SCIO The UART of the simulating computer can freely be chosen When the modem answers to the simulator the activity can be checked by ob
80. gle e Multiple access to point of failure microcontroller Opportunity Threat e Security options may be e Prone to hacking extended to more powerful gateway firewall P masquerading e Independent from remote host s hardware 2 3 3 3 Internal use of non internet protocols A good number of implementations let the microcontroller communicate with a non IP protocol In many cases it is a simple serial protocol and in very many cases it is proprietary In those cases the embedded devices can only communicate via internet with the appropriate gateway The gateway itself implements the server but gathers information from the embedded devices behind The main advantage is that only the gateway has to implement internet protocols All embedded devices behind the gateway may run an easier protocol Consequently this solution is advantageous when a significant number of low end embedded devices have to be connected to the internet Designer Reference Manual DRM049 Rev 0 26 Connecting Embedded Applications to the Internet MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Internet Connectivity uC uC uC Gateway Internet Remote Host Proprietary Protocol gt y Ethernet Figure 2 4 Gateway based Connectivity with Internal Use of Non internet Protoc
81. he States for Modem Input Comparison DRM049 Rev 0 66 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Modem Communication 6 2 4 Processing of Incoming Data In the initialization phase SCl interrupts can be directed to the appropriate function because the possible answers to the strings sent are known They can be concluded from the modem command set 8 and its result codes After the modem is initialized the ISR is directed to Modem_Receive if either the remote activation or the connection of a remote host is allowed Modem Receive checks for the first character of the expected string and calls Modem_InpComp for the rest of the string Having received the matching response the modem is in data mode see Figure 6 3 The Modem State Machine Thus it is transparent to the application The callback function in physical c is processed to redirect the interrupt service routine to upper layers and mark the physical link as established 6 2 5 Modes of Modem Operation As discussed in 2 3 Internet Connectivity there are different techniques of how to connect to an embedded web server The connection mode is chosen during the modem initialization as the modem is instructed to react differently on incoming calls Additionally the interrupt service routine shall call different functions depending
82. ialup e TFTP file server e SMTP mail client e UDP Client for portal based solutions Transport Layer e Transport Control Protocol TCP e User Datagram Protocol UDP Network Layer e Internet Protocol IP e Internet Control Message Protocol ICMP Net to Host Layer e Point to Point Protocol PPP e Generic modem drivers e Ethernet controller drivers for Crystal CS8900 e Address Resolution Protocol ARP DRM049 Rev 0 Designer Reference Manual MOTOROLA emBetter A Short Overview 15 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc emBetter A Short Overview gt HTTP smTP Ttrrp Proprietary n i UDP Q server client server f S client S gt A socket interface 5l TCP UDP 3 E IP ICMP 18 le net to host layer interface PR ARP 7 Q Z PPP Ethernet oO v A7 modem hardware Figure 1 1 emBetter Protocol Suite 1 2 Target Platforms The emBetter protocol suite is optimized for use in 8 and 16 bit microcontrollers and is an efficient platform for internet connectivity in modular systems The original implementation was done for a Motorola HCS12 microcontroller under Metrowerks CodeWarrior V3 0 1 3 Portability The use of pure ANSI C and a minimum of external library functions make the emBetter protocol suite extremely portable to a variety of other compilers and microc
83. ight be an incoming call on the modem s extension This call is not answered by the modem but initiates the dialup to the predefined extension number of the ISP e A signal on one of the microcontroller s digital ports may serve as an alarm to initiate the dialup Table 2 5 SWOT Analysis of ISP based Connectivity With Dialup Strength Weakness e ISP offers web services e ISP has to assign a static IP or Mail access further solution for telling address to host e Microcontroller only online after dialup security against hacking Opportunity Threat e Alert function likely to be e ISP might change dialup implemented e In times of heavy traffic fail of e Independent from remote host s connection possible hardware e Independence from different ISP 2 3 4 3 ISP based connectivity with a Portal Server uC ISP Portal server Remote Host Modem uC Modem bank ISP ar D ad Internet ie a aie coe Figure 2 7 ISP based Connectivity with a Portal Server The use of a portal server can be understood as a dual server architecture In Figure 2 7 ISP based Connectivity with a Portal Server several embedded web servers are connected to the Internet DRM049 Rev 0 Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 29 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Conne
84. in the home office In this case the IP address is assigned by the ISP However it is also possible to run a web server via a dialup line and an ISP The main challenge is that the web server has to dialup himself to the ISP The ISP does not provide the functionality to connect to one of its customers Additionally the web server does not have a fixed IP address The remote host shall be able to initiate the dialup process and afterwards the microcontroller has to communicate its IP address to a connecting host The necessary steps are shown in Figure 2 6 Communication Initiation of the emBETTER Implementation 1 Remote activation of the microcontroller 2 Microcontroller 3 Negotiation of 4 Sending of a 5 User clicks 6 User connects to the the Internet memotouser gt onthe link inthe connected to the ISP connection containing IP memo microcontroller Figure 2 6 Communication Initiation of the emBETTER Implementation Designer Reference Manual There are two possibilities for the activation of the microcontroller 1 of Figure 2 6 Communication Initiation of the emBETTER Implementation DRM049 Rev 0 28 Connecting Embedded Applications to the Internet MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Internet Connectivity e It m
85. ion Handling 56 5 7 Call Structure of Function ppp_entry 58 6 1 The Modem Initialization Strings 65 6 2 The Modem AT Commands 00eee cease 65 Designer Reference Manual MOTOROLA List of Figures 11 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc List of Figures 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 10 6 11 6 12 6 13 6 14 6 15 6 16 6 17 6 18 6 19 6 20 6 21 6 22 6 23 7 1 7 2 7 3 7 4 7 5 7 6 7 7 Designer Reference Manual The Modem State Machine 00 eee eeaee 66 The States for Modem Input Comparison 66 The Simplified PPP State Machine 73 The Supported LCP Negotiation Frames 75 Negotiation of IP Addresses with LCPC 77 Reading he PPPS vs ctoweswe baie ddd sb Cee tis 80 emBetter Socket Structure 0000s 85 Design of a sockaddr Struct ous ccc e iw ewianisisccuceecans 86 UDP Data SOAGE erada pi a eee le saeeew Res 87 Function Calls To When Sending UDP Datagrams 88 The Possible States for TCP Sockets 90 TCP Segment Stored in st_buf index cData 93 Function Calls Caused by soc_write 94 HTML Page Providing Static Content 97 Organization of HTML File Names and String Pointers 98 Dynamic Content in an
86. ion On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Structure and Interfaces project itself consists of the software modules shown in Figure 5 1 Folder Structure of the emBetter Protocol Suite Figure 5 2 The Project Structure of the emBetter Protocol Suite shows their internal relationship The module out_buffer timeout and debug are not shown in this figure as they provide overall utility functions Main application Acprd_main c smip c Application http c Layer html c T He Top UDP socket c IP Internet ICMP Tit ee PHY Interface Handler physical c Neti Network drv_modem c Cl S s12_sci c Hardware ye Figure 5 2 The Project Structure of the emBetter Protocol Suite These modules are shortly described in Table 5 3 Overview of Functions in buffer c for a complete discussion see Section 6 Layer Implementation of emBetter 5 2 3 Software Interfaces Software interfaces are the key to data encapsulation Data encapsulation means that data stored in certain memory spaces is only accessible through functions and not through direct memory access As DRM049 Rev 0 Designer Reference Manual MOTOROLA Overall Implementation of emBetter 51 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter a result the format to pass on data is specified an
87. ity to generate the Preparing the data to transmit content goes here void soc_write cSock amp cData DATA LEN lt ite the generated data switch net_errno N case ERR_SOC_OK cReturn HTTP_DYNS OK break case ERR_SOC_AGAIN A cane ERR UNACK gt exception handling case ERR_SOC_NOBUFS cReturn HTTP_DYNS_PROGRESS break default cReturn HTTP_DYNS ERROR return cReturn Figure 6 20 Function Template for Generating Dynamic Content 6 9 Simple Mail Transfer Protocol 6 9 1 Overview The Simple Mail Transfer Protocol SMTP is the protocol that handles the communication between mail servers and outgoing mails from a mail client to a mail server As a client implementation it provides an efficient means to trigger events alarm or alerts 6 9 2 Applications Demonstrating the SMTP Functionality emBetter implements the Simple Mail Transport Protocol in a pure client version The reference design contains two examples to demonstrate the benefits of SMTP Designer Reference Manual DRM049 Rev 0 102 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Simple Mail Transfer Protocol e the e mail alerter When an occurrence causes an alert for emBetter the SMTP client is advised to connect to the Internet Service Provider to send an e mail to the address stored as recipient for
88. l for inter device communications The OSI model provides a conceptual framework for communications between computers but the model itself is not a method of communication Actual communication is made possible by using communication protocols The protocol is a formal set of rules and conventions that governs how nodes exchange information over a network medium Used protocols in the Internet are the Internet Protocol IP with the Internet Control Message Protocol ICMP the Transfer Control Protocol TCP and the serial communications support SLIP Serial Line Internet Protocol and PPP Point to Point Protocol The set of programmes used for Internet communication is usually referred to as the Internet Protocol Stack DRM049 Rev 0 Designer Reference Manual MOTOROLA Basics of Implementation 35 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation TCP IP was already established while the ISO networking standards were evolving Nevertheless TCP IP protocol can be described with the ISO OSI model The principle behind layering is each layer hides its implementation details from the layer below and the layer above Each layer on the transmitting node has a logical peer to peer connection with the corresponding layer in the receiving node This is accomplished through the use of encapsulation Figure 3 2 ISO OSI Reference Model and TCP IP Reference Model a
89. lel applications can send data over the socket interface without disturbing each other s communication 5 4 Buffer Handling and Data Flow To understand the handling of buffers in emBetter it must be distinguished between the data flow of outgoing and incoming data Outgoing data is data of an application or process that needs to be transmitted by the network interface Incoming data is data that arrives Designer Reference Manual DRM049 Rev 0 56 Overall Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter Buffer Handling and Data Flow asynchronously at the serial communication interface and needs to be processed by different functions of the protocol stack The aim of the buffer management is to provide common memory spaces for different functions in order to reduce the amount of data copied between different layers of the stack For memory spaces that are accessed from different functions the access must be verified in order to eliminate the risk of overwriting data 5 4 1 Overview of Buffer Variables 5 4 2 Incoming Data DRM049 Rev 0 Two main buffer variables exist in emBetter see Table 5 2 Overview of Buffer Variables Table 5 2 Overview of Buffer Variables buffer name type Purpose PPPbuffer array of UINTS contains of received PPP frames until processed by all protocols st_b
90. ly run a complete TCP IP protocol stack with all of its opportunities Especially saving the TCP segments for retransmissions and handling acknowledgements is often not possible caused by a lack of RAM or CPU time restrictions In these cases the connectionless User Datagram Protocol UDP offers an opportunity to make use of the internet infrastructure without the need for a complete implementation of the reliable and thereby capacious TCP with all of its control structures After a remote request for data an answer datagram is sent and the datagram information is discarded If the remote host DRM049 Rev 0 106 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter UDP Applications does not receive the answer due to network problems or the microcontroller being overburden he has to ask again for the packet Thereby all control of the communication is transferred from the low performing microcontroller to the by far more performing remote computer running the UDP application This application has to check if all required packets arrive and it has to prepare the raw data fora suitable presentation im Peer A OF x Port 0 00o o Port B rT WM wf fF ff Olafs Lichtorgel Speed sti gt i Start m Connection parameter RemotelP f inf 2f sf 7 Remote Port 1080 Loc
91. n Process emBetter implements Password Authentication Protocol PAP for PPP authentication due to performance reasons The authentication process depends on the kind of connection in progress If the microcontroller connects actively to an Internet Service Provider the remote host is taken as authenticated by the availability under the extension number Authentication requests are positively answered no matter which password and user information they contain For authentication at the ISP the microcontroller transmits the user name and password specified for this connection in netGlobal h If however a remote host opens a connection channel emBetter requests a valid authentication for this host The transmitted password is compared with the predefined IN_PASSWORD also in netGlobal h If this password matches the negotiation of the IP address is set active The negotiation of the IP addresses is not possible before a successful authentication as the remote host s IPCP and higher layers packets are discarded DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 75 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter These technique guarantees a certain security standard against intrusion 6 3 5 IPCP Negotiation The negotiation of the IP addresses is handled as depicted in The assignment of addresses
92. nce Manual MOTOROLA Layer Implementation of emBetter 81 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter For performance reasons the constant fields of the IP header are defined on module initialization Their values are listed in Table 6 5 Constant Values in IP Header ip write writes only the header fields that are different for each datagram during the sending process such as e IP length e Protocol type e Checksum e Destination address Table 6 5 Constant Values in IP Header Header field Value name value Comments Version IP DEFH_ VERSION 4 this Implementation supports only IP4 Header length IP DEFH HEADLEN 5 no options header length 5x4bytes TOS IP_DEFH_ TOS 0 default value Identification IP DEFH ID 0 No significance since no fragmentation is supported Fragment Offset IP DEFH_ FRAGOFF 0 No significance since no fragmentation is supported Time To Live IP TTL 0x20 a standard value can be modified in socket h 6 4 4 Restrictions Regarding the IP Specification Designer Reference Manual In emBetter IP serves only to receive and transmit datagrams Even though IP must theoretically be able to fragment data to meet the maximum transmit length of the data link layer fragmentation is not supported as it is assumed that the maximum transmit length is known at all levels of the stack Th
93. nd Protocols shows the TCP IP stack in terms of the OSI layers layers in layers in ISO OSI TCP IP protocols in TCP IP protocol stack reference mode i reference mode layer 7 application application http ftp smtp pops telnet tftp layer 6 presentation layer 5 session layer 4 transport transport tcp layer 3 network internet arp bootp dhe layer 2 j _ data link network Ethernet Wel ss layer 1 physical host to net 802 3 802 11 Figure 3 2 ISO OSI Reference Model and TCP IP Reference Model and Protocols In Figure 3 3 HTTP Packets Via a Serial Link Takes 51 Bytes Plus a Variable HTTP Header HTTP data is transported via a serial line Each layer in a receiving machine gets received data from the layer below analyzes and removes the appropriate header and relays them to the layer above Similarly each layer in a sending node gets data from the layer above builds and adds its header and transmits the packet to the layer below Designer Reference Manual DRM049 Rev 0 36 Basics of Implementation MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation Layered Protocol Models ee Eam 5 Byte A 20 Byte 20 Byte roe 3 Byte Figure 3 3 HTTP Packets Via a Serial Link Takes 51 Bytes Plus a Variable HTTP Header
94. ne protocols such as SLIP ref or PPP ref Basic implementations are well possible with 8 Bit microcontrollers Table 2 2 SWOT Analysis of Direct Connectivity Without Internet Protocols Table 2 1 SWOT Analysis of Direct Connectivity Without Internet Protocols Strength Weakness e Simple to implement and debug e Alert function nearly impossible e High security by unknown e No simultaneous connections address e Simple connection via uCs SCI Opportunity Threat e No costs for Internet Service e No use of the Internet Provider e Only simultaneous technology transfer of the two hosts possible Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 23 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet Table 2 2 SWOT Analysis of Direct Connectivity Without Internet Protocols Strength Weakness e Simple to implement and debug e Additional protocol overhead e High security by unknown e Matching connection standards address necessary e Simple connection via uCs SCI e Alert function nearly impossible e Use of internet based e No simultaneous connections development and application tools Opportunity Threat e No costs for Internet Service e No use of the Internet just the Provider same tools e Only simultaneous technology transfer of the two
95. ned above HTML pages or any object that HTTP controls are stored with their data and their filenames in htm1 c The content of each file is assigned to a constant variable This variable does not only contain the content of the file but also the HTTP header This eases the adaptation of the HTTP headers to different file types An example of a HTML file assigned to a variable is shown in Figure 6 16 HTML Page Providing Static Content const UINT8 index_html HTTP_DEFAULT_HEAD lt html gt lt head gt lt meta http equiv Content Type content text html charset iso 8859 1 LS Body lt body bgcolor white link 0000a0 vlink 0000a0 alink 0000a0 gt lt div align left gt lt table border 0 cellpadding 0 cellspacing 0 bgcolor white End of text lt tdoadnbsp td tr table body html gt pe Figure 6 16 HTML Page Providing Static Content DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBetter 97 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Designer Reference Manual The constant HTTP_DEFAULT_HEAD is a very basic HTTP header that can be used for plain HTML pages as well as pages with included graphics The array pFileNames contains the filename strings that a remote user may request via his browser In the structure HTML files data pointers to the seve
96. not been negotiated yet Packets for link termination and maintenance Code 05 to OB are directly answered Packets containing codes from 09 to OB are rather unusual but as they are necessarily to be implemented in order to fulfill the RFC they are taken into account Their processing is independent from the current link state and it does not require further investigation Designer Reference Manual DRM049 Rev 0 74 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter The Point to Point Protocol PPP Ox 2 E7 2 5 QO E os Lys gt oo 3 E E 2 3 o o3 E SE e Bgas 55 5 Sss 2 S Pea f 8 83 52556 65g 668 8 25 p 7E FF 03 Co 21 a 7E Configure Request 01 01 04 Maximum Receive Unit Configure ACK 02 02 06 Asynchronous Control Character Map Configure NAK 03 03 var Authentication Protocol Configure Reject 04 05 06 Magic Number Terminate Request 05 07 02 Protocol Field Compression Terminate ACK 06 08 02 Address and Control Field Compression Code Reject 07 OD var Callback Protocol Reject 08 Echo Regest 09 Echo Reply 0A Discard Request 0B Figure 6 6 The Supported LCP Negotiation Frames 6 3 4 Authenticatio
97. ns the outgoing traffic rather than new connection requests 6 6 5 4 Retransmission and timeouts DRM049 Rev 0 An additional challenging aspect in TCP implementation is the memory management As a connection oriented and reliable protocol TCP includes the repeated transmission of a segment as long as there is no acknowledgement for this segment and as long as the timeout for this transmission has not elapsed These retransmissions make it necessary to store the outgoing data as long as there is no acknowledgement In order to ease sliding window functionality of TCP emBetter sets the window size to 1 This means that the remote host has to send acknowledgements for every segment received Each segment is kept in the memory and no new segment is transmitted until the acknowledgement is received Retransmissions are triggered by a free running counter that is incremented every 10 ms This free running counter in emBetter tcp tick is linked to the ISR of a hardware timer and increments the 16 bit variable iTCP_tmr Each socket provides the variable stSocket index iTick that represents the number of increments before a segment must be retransmitted This allows dynamic calculation of the retransmission timeout RTO In emBetter the RTO is set to a default value of 1000 ticks It is set by the preprocessor definition TCP_RETR_TICKS in socket h The central function of the socket module is soc_entry In this fun
98. nternet is waiting for clients to requests for a service The server analyzes and executes an action depending on the request mostly including an answer to the request After the action the server returns into waiting state expecting the next request Designer Reference Manual MOTOROLA Basics of Implementation 39 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Basics of Implementation 3 5 Ports and Sockets Two types of servers are commonly differentiated 8 e Iterative servers cannot treat any other request as soon as they are responding to one request This of course is not favorable when it is likely that more than one client sends requests at a time e A concurrent server however performs an additional step When the request arrives a second server is started to handle the entire procedure The original server remains free for further requests Thus concurrent servers are advantageous as they can process more than one request at a time leveraging performance and flexibility of the system However the implementation of this concurrent response poses additional challenges to the implementation in an embedded system In most cases however this concurrency is realized with the help of the classical socket approach Figure 3 6 Ports and Sockets for Concurrent Servers client host 1 IP address 193 196 182 232 HTTP client port 1043 port 80 CN passive
99. nual MOTOROLA Layer Implementation of emBetter 103 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter 6 9 5 Function Calls Designer Reference Manual 220 abc de SMTP server ready HELO xyz de 250 xyz de pleased to meet you MAIL From lt adam xyz de gt 250 lt adam xyz de gt Sender ok RCPT To lt eva abc de gt 250 lt eva abc de gt Recipient ok RCPT TO lt tom abc de gt 250 lt tom abc de gt Recipient ok DATA 354 Enter mail Hallo Eva hallo Tom Beispiel f r den Mail Versand mit SMTP Adam 250 Mail accepted QUIT 221 abc de delivering mail VVVVVVVVVV VV VV VV VV NDANAAAANRWAN AN AN AMNAN Figure 6 21 SMTP Communication Between Mail Client and Mail Server As most fields in the mail header are optional only the mail subject the sender and the receiver are introduced in order to reduce processing time The timestamp of the mail can be included by the next SMTP server Therefore the time field is left empty as most microcontroller systems do not have a real time clock When sending an electronic mail the SMTP connection is not explicitly opened but the SMTP_Write function is called transmitting a pointer to the structure of the mail information This function checks the status of the Internet connection connects to a socket and calls the SMTP_Process procedure when the connection to the SMTP server
100. o www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Modem Communication 6 2 6 Functions Related to the Modem Communication In this chapter the functions on the lowest communication layer are listed up with their function calls and the variables they access Table 6 1 s12_sci c Functions Variables Function name Return value Parameters Functions called accessed Description initSClO void UINT16 EnEvent SerFlag Initialization of SCIO EnUser sci_hwEnDi initSCl1 void UINT16 EnEvent SerFlag Initialization of SCI1 EnUser sci_hwEnDi ISR_sciO void void SCI_0_IntTx_Callb Interrupt service SCI_O_IntErr_Callb Routine for SCIO SCI_0_IntRx_Callb isrErrorHandler void void channel Default ISR SCI_O_IntErr_Callb CallbackFunc void _Do_Nothing Callback function upon SCI error SCI_O_IntRx_Callb CallbackFunc void _Do_Nothing Callback function upon SCI receipt SCI_O_IntTx_Callb CallbackFunc void _Do_Nothing Callback function upon SCI transmit sci_hwEnDi void UINT8 EnUser enables or disables the SCI depending on EnUser sci_sendChar UINT8 UINT8 UINT8 EnUser Sends a character via the SCI sci_setCallback void void pFunction SCI_O_IntRx_Callb Sets the callback UINT8 UINT8 SCI_0_IntTx_Callb function for SCI_O_IntErr_Callb interrupts to the specified function DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation of emBet
101. odem c g modem_receive modem _ dial nodem_hangUp modem_inpComp modem_init t modem _open d modem_close J modem _ write U B physical c g E PPP c E SMTP c E socket c 1 HTTP c j HTML c SNADOMAODOHNTOOOFP BROOM RDOOTANNY BOO Figure 7 7 Code Coverage Information DRM049 Rev 0 Designer Reference Manual MOTOROLA Test environment 117 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment Designer Reference Manual DRM049 Rev 0 118 Test environment MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 8 1 Web Resources DRM049 Rev 0 w1 w2 w3 w4 w5 w6 w7 w8 w9 w10 w11 w12 Section 8 Sources http www arcor de http www ba loerrach de stzedn http www freenet de Information about CodeWarriorTM updates demo keys and demo downloads http www metrowerks com Motorola microcontroller home page http www motorola com mcu http germany motorola com pressetool presse asp details true amp all true amp MsgID 4AE2DFEB 43F0 4A3B 9CC6 AC2E7B 5D2925 http www elektronikladen de ZyXEL Inc ZyXEL U 1496 Series Modems User s Manual ZyXEL Communications Corp 2001 ftp ftp europe zyxel com u1496s document u1496s_v1 _UsersGuide pdf Statistisches
102. ols Table 2 4 SWOT Analysis of Gateway based Connectivity With Internal Use of Non internet Protocols Strength Weakness e Cheap and easy access to e Closed system of embedded microcontroller device and gateway e Dependence on gateway single point of failure Opportunity Threat e Web Server functionality runs on e Lack of portability powerful gateway e Security options may be extended to more powerful gateway firewall P masquerading e Independent from remote host s hardware 2 3 4 ISP based Connectivity 2 3 4 1 Overview Internet service providers play a major role in the architecture of the public internet The do not only proved the access to dialup hosts but also provide IP addresses and DNS support They may offer additional services such as web server capabilities DRM049 Rev 0 Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 27 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet 2 3 4 2 Dialup to an Internet Service Provider uC Internet Service Provider Remote Host Modem uC Modem bank ISP oy Internet ue t0 Ethernet 5 D Gp N ep Figure 2 5 Dialup to an Internet Service Provider The dialup connection is most common for client applications for example web clients
103. on the initialization 6 2 5 1 Direct Dialup case 5 DRM049 Rev 0 In this mode of operation the embedded application actively opens a connection to an Internet Service Provider This case is similar to client program operations known from desktop computers The application asks the modem to connect to the ISP by calling modem_open The modem dials the ISP number and sends the corresponding answer strings depending on the connection state As long as the timeout for the connection has not expired the cModStatus variable is in state MOD_DIALING As soon as the connection is established cModStatus is changed to MOD_DATA Now the modem is transparent and the application may negotiate their parameters Designer Reference Manual MOTOROLA Layer Implementation of emBetter 67 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter A connection to the ISP can be established in any mode of operation for example for sending an alarm message to an SMTP server The settings for the connection for example the extension to dial are described in netGlobal h 6 2 5 2 Direct Internet Based Connectivity case 2 When the embedded application acts as a dial in server remote devices are allowed to connect This mode of operation is activated by enabling the ALLOW _DIAL_IN option in netGlobal h It is indicated with Auto Answer LED on the modem front panel a
104. ontrollers The fitting to the hardware is performed in one C and one header file leading to a smooth design flow Adaption to the different instruction sets of modems is being done in a single header file The PPP parts of the protocol suite were tested with the German internet service providers ISP arcor w1 and freenet w3 The connectivity with telephone based dial in was done with PCs running Microsoft Windows 98 and Windows 2000 Designer Reference Manual DRM049 Rev 0 16 emBetter A Short Overview MOTOROLA For More information On This Product Go to www freescale com 1 4 Modularity 1 5 Scalability Freescale Semiconductor Inc emBetter A Short Overview Modularity The modules of the emBetter protocol suite run as independent as the protocol definition allow The interfaces between the protocol layers follow the common winsock standard init open close read write Other physical layers for example CAN or LIN can be supported On the higher layers additional protocols such as Domain Name Service or IPsec are under development In case that a less performing target hardware is being used the protocols and functions can be switched off before compilation This holds true for add in protocols such as ICMP or SMTP Moreover buffer and memory sizes can be scaled for optimal use of resources and full scalability All parameters are described in the text files of the project However in the pre
105. options to be set The most important options are shown in Figure 6 6 The Supported LCP Negotiation Frames These options are negotiated during link establishment phase They include different compression algorithms for the communication phase the preferred authentication protocol and further options regulating the link establishment and maintenance The function ppp _handleLCP parses through the option fields of received PPP packets as their length is variable pOpt ionRead points to the actual option to be evaluated Its type is cast depending on the option type For the analysis of LCP options requested by the remote host the following have to be distinguished e If the option is not known or forbidden disabled they are directly collected in PPPbuf fer fora reject answer The remote host who receives this reject packet stops negotiating the rejected options for the further process The only exception is the case where the remote host relies on this option For example if a encrypted password is required but rejected from the microcontroller the remote host will continue to ask for this option e Incase that the option is supported but do not match the preferred value stored in the sOptionState array are sent in a NAK packet e If all requested options match a positive reaction is stored in the cValid field of the negotiated option in soOptionState An ACK answer is prepared followed by a request of all options that have
106. otypes which may be included in other files set_modem h is the file in which modem specific changes may adapt emBetter to the implementation environment Here the information about the telephone line connection is stored as well as the specific modem commands In Figure 6 1 The Modem Initialization Strings the modem initialization strings as well as the respective modem answers are shown The explanations for the expressions can be found in the modem manual Designer Reference Manual DRM049 Rev 0 64 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Modem Communication if ALLOW _DIAL_IN Deactivate Auto Answer if DIAL_IN is forbidden __DECL MODEMSET_H_ const SINT8 const InitSeq NUM_INIT_COM AT FACTSET NO_ECHO SPEED HUP_CMD MOD_EOL AT TIMEOU SPK_ON SPK_TIME ERR_CTL MOD_EOL AT WAIT_ANS FLOW_CTL MOD_STD RSLT_CODE MOD_EOL AT NUMERIC NO_RING IGNOREDIAL MOD_EOL telse __DECL MODEMSET_H_ const SINT8 const InitSeq NUM_I const SINTS8 AT const SINT8 AT TIMEOUT SPK const SINTS AT const SINTS AT tendif NIT_COM FACTSET NO_ECHO SPEED HUP_CHD MOD_EOL SPK_OFF TIME ERR_CTL MOD_EOL FLOW_CTL MOD_STD RSLT_CODE MOD_EOL NUMERIC NO_LRING IGNOREDIAL MOD_EOL __DECL_MODEMSET_H__ const SINTS const InitAns NUM_INIT_COM i const cons
107. out the current state of the microcontroller Designer Reference Manual DRM049 Rev 0 114 Test environment MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Test environment Simulation environment including pin values stack information pending interrupts and events This tool can be of great value if due to a programming error different microcontroller modules try to control the same pin or expected interrupts do not occur Furthermore a stack overflow may be detected or pointers with wrong addresses T Components WatchPoints MCCNTUnderflow Ox16c1b BreakPoints TCNTOverflow Oxb9599 B Stack Compare2 Oxb95d4 S F moderm_init H 0 pCallit QO clndex QO cRetV al Source Information sA phy_init sA Ppp_init SA soc_init http_init F sA main SA _Startup 38 Symbol Table 33 RTK Exceptions 858 Object Pool 9 10 Register Figure 7 5 Metrowerks Inspector Component 7 3 3 3 Profiler The Profiler is very useful when multiple applications run in parallel ona microcontroller with unexpected behavior This tool informs about the percentage of CPU usage for the different modules and functions This allows observing if certain procedures block the CPU or if an Interrupt Service Routine is entered excessively often or not at all DRM049 Rev 0 Designer Reference Manual MO
108. plementation the end condition is set to the string Refresh and the number of end conditions is set to 1 as only one page containing POST variables is realized Similar to the parsing of HTML files the fields to look for are defined in ppost_field and the corresponding function pointers are defined in ppost_fieldfunc The name of the constant to indicate the number of fields is HTTP_NUM_FIELD Upon match of a field name in the POST string the corresponding function is called Designer Reference Manual MOTOROLA Layer Implementation of emBetter 99 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter One restriction applies to this implementation Field names must be unique throughout the HTML project to allow parsing for the field variables 6 8 Handling of Web Pages The HTTP server parses each file for the start tag dyn_pref and the end tag dyn_suff set in http c Data between the tags is not being sent but examined for a valid function name The tags can be modified but it must be ensured that they don t match any tag defined in the HTML standard W3Schools HTML tags 2002 In the current implementation the start tag is lt hc12 and the end tag is gt If the server finds the start tag it sends all data up to the tag and then tries to call the function that is defined between the tags The following example shows HTML source
109. ral string constants and the lengths of the strings are stored To be compliant with common browser entries the filenames have to start with a and end with zero The string pointers and the filenames have to be at the same position in both arrays An example is shown in Figure 6 17 Organization of HTML File Names and String Pointers const UINTS pFileNames stct_File HTML_files HTML_NUM_FILES stw gif sete same lt itm1NO positions 2st TR file names are zero terminated o file names start with and can also contain paths Figure 6 17 Organization of HTML File Names and String Pointers Figure 6 17 Organization of HTML File Names and String Pointers shows the formal requirements to register a HTML file in the HTTP server Some additional settings are required e If the file represents a HTML page the information consists of ASCII characters terminated by a zero character In this case the first value in the structure HTML_files can be set to zero This indicates that the length of the file can be computed during initialization of the HTTP server If the file is a binary file for example a gif image it might also contain zero values Therefore the size that includes the HTTP header and the data must be specified e The constant HTML NUM FILES defined in html h represents the number of the files In the example above HTML _NUM_FILES is set to 6 DRM049 Rev 0 98 Layer Implementa
110. ransmitted the request will be repeated at a later time After having received the handle the protocol header is generated in the memory cells of each protocol layer After having done this for all relevant protocols the PPP module generates the frame checksum and puts it in the frame trailer Now the frame is transmitted byte by byte via the serial interface After the transmission is successfully completed the handle is released This approach combines three advantages e No copying of the user data is required e Zero length packets can easily be handled e The data transfer between the layers is modular ppp_ write can be replaced with Ether write However this concept is not feasible in all cases When the data is to be transmitted via a companion chip for communication for example an Ethernet controller with separate output buffers the frame has to be DRM049 Rev 0 Design Techniques for emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Design Techniques for emBetter Unified Protocol Interfaces copied from the microcontroller into the Ethernet controller This is commonly called a One Copy Approach 4 3 Unified Protocol Interfaces The layered protocol model allows a platform independent communication with a straightforward change of single protocols In the emBetter protocol stack a protocol provides at least five functions to initialize the p
111. rotocol to open and close an instantiation of the protocol and to read and write in the instance of the protocol This functionality may be called by the upper layer with five identical function calls On the data link layer of the Point to Point Protocol PPP those are e ppp init e ppp_open e ppp _close e ppp write e ppp read 4 4 Socket Interfaces TCP and UDP are the top level protocols of the communication portion of the internet stack For that reason a software interface needs to be implemented that permits users to write applications for Neither does the specification for TCP defined in RFC793 nor the specification of UDP in RFC 768 provide a standard API However RFC 793 only recommends the implementation of basic functions w11 A widely used API for both UDP and TCP communication is the socket interface used in the BSD UNIX operating system 2 Over the years it became a de facto standard for many internet stack implementations such as Winsock Therefore emBetter provides an API similar to the DRM049 Rev 0 Designer Reference Manual MOTOROLA Design Techniques for emBetter 45 For More information On This Product Go to www freescale com Freescale Semiconductor Inc Design Techniques for emBetter BSD socket API with the socket functions shown in Table 4 1 BSD Socket Function Implementation in emBetter Table 4 1 BSD Socket Function Implementation in emBetter BSD socket API emB
112. s and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts Motorola does not convey any license under its patent rights nor the rights of others Motorola products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the Motorola product could create a situation where personal injury or death may occur Should Buyer purchase or use Motorola products for any such unintended or unauthorized application Buyer shall indemnify and hold Motorola and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part MOTOROLA Motorola and the Stylized M Logo are registered in the U S Patent and Trademark Office digital dna is a trademark of Motorola Inc All other product or service names are the property of their respective owners Motorola Inc is an Equal Opportunity Affirmativ
113. s a main stepping stone on the way to ubiquitous computing 6 Where the Internet may have been a dedicated network for computer data exchange in its infant years today more and more small non PC based intelligent machines are connected to the Network of Networks The prognosis is that by 2005 the amount of non PC users on the Internet will far exceed the amount of PCs For embedded internet connectivity various trends can be observed 2 1 1 Maturing the Products The market for embedded internet is maturing rapidly Being a research driven discipline for quite a while internet protocol suites for embedded systems are widely available as stand alone software packets or included in real time operating systems They are widely deployed and reliable Performance is increased and cost is reduced as semiconductor device dimensions continue to scale 2 1 2 Maturing the Market DRM049 Rev 0 The market for embedded internet is rapidly following the technical advances Maturity of the market can be identified by a broad variety of products and solutions as well as by a fine differentiation of market Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 19 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet players However this makes markets more complicated and inter operability is at stake
114. s detected with the HDLC frame delimiter the IS_FRAME flag is set This flag is polled within ppp_entry which is called periodically by the main loop Complete frames are analyzed with the actual protocol and if necessary passed to higher layer protocols with callback functions see 6 3 The Point to Point Protocol PPP for details If the data is addressed to the actual protocol the answer is directly generated Designer Reference Manual DRM049 Rev 0 48 Design Techniques for emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Designer Reference Manual DRM049 Section 5 Overall Implementation of emBetter 5 1 Overview The emBetter TCP IP protocol stack is designed for use with 8 and 16 bit microcontrollers with limited resources that normally don t run an operating system The stack was first implemented on a Motorola HCS12 a low cost but highly integrated 16 bit microcontroller It is designed as a stand alone stack but is modular and portable However it can also be used together with a small operating system for example OSEK 5 2 Structure and Interfaces 5 2 1 Project Structure The folder structure of the Internet protocol stack is derived from the usual CodeWarrior structure When creating a new project in the Sources folder there is a simple main procedure and the Start12 file To include the Internet connectivity the emBetter
115. serving the LEDs of the modem Additionally the traffic may be logged in the command window e The baud rates of the terminal and the simulated SCI may not match due to a very high or very low computer performance Running the system with different combinations should solve this problem e After checking the correct modem initialization see Figure 7 4 Data in the Command Window the Show Protocol option should be turned of to preserve performance e The RS232 interface of an evaluation board is usually meant to connect to a terminal Therefore attaching a modem requires a null modem cable When simulating the microcontroller on a PC the modem is linked with a usual serial cable e During the implementation of the FCS focus was laid upon cycle accuracy As the simulation of parallel processes can take an important amount of time on slow computers the simulated CPU might be by far slower than real hardware This can lead to problems during the PPP negotiation as the provided characters may not be recognized correctly Further on when sending a web page to a connected client the browser can stop communicating assuming the connection to be interrupted Therefore the simulating computer should provide sufficient resources frequency of about 2GHz memory of at least 256MB and should not run many parallel processes 7 3 3 Useful Debugging Components 7 3 3 1 Terminal During the simulation of the emBetter protocol suite the
116. size and run time behavior Since it is written as target specific code it is often not portable to other targets 2 3 Internet Connectivity 2 3 1 Overview DRM049 Rev 0 There is a good number of techniques how to connect devices to the internet 7 The presented solutions See Figure 1 1 emBetter Protocol Suite concern the overall architecture at data link and networking layer but do not consider the physical layer Depending on the implementation the embedded device acts as client who connects to a server when an event occurs or it is a server that is called by remote Designer Reference Manual MOTOROLA Connecting Embedded Applications to the Internet 21 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Connecting Embedded Applications to the Internet devices in order to read the data stored by the device or to change the settings of the device embedded internet application gateway connectivity connectivity via via internet EPEA internal use of non internet protocols direct connectivity internal use of direct dial internet up protocols Sintetrre non protocol internet based via protocol serial line based SLIP PP dial up via portal server a with IP IP masque rading masque rading Figure 2 1 Architectures of Internet Connectivity 2 3 2 Direct Connectivity uC Remote Host Modem uC
117. sreneerericieredrerdunerraki 21 Internet Connectivity aasan sasaaa eea 21 Section 3 Basics of Implementation GWE oc ai aki a a aioe deba d a a a k ena ia a a E E tise 33 Packet SwWIiGhING esaia cusasa dere sinew iA 33 Layered Protocol Models nananana anaana 34 Client Server Model 2 220144 So deee nann 39 Ports and Sockets annan ana anana aa 40 Section 4 Design Techniques for emBetter EB e Aa E E E E E E E E ET E A EN 43 Designer Reference Manual MOTOROLA Table of Contents 7 For More information On This Product Go to www freescale com Designer Reference Manual Freescale Semiconductor Inc Table of Contents 4 2 4 3 4 4 4 5 4 6 5 1 5 2 5 3 5 4 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 10 7 1 T2 Zero copy Approach a an anana aaae 43 Unified Protocol Interfaces 1 0406 ee so wowuw ss vaewoaeveds 45 Socket Interfaces 00 00 ees 45 Callback PONG os fac n ci eeeeetede wn danandiuekeces 46 BNI s tel te doe chr oc dea ree dele toe dm deh ok lee weet 47 Section 5 Overall Implementation of emBetter FO 5 65 64 bb od hb oh 8 erara 49 Structure and Interfaces jess se et eset 2 ieee os be eeee ens 49 Exception Handing 6 65 bine Stee be de dd deb ed ee ee ae ews 55 Buffer Handling and Data Flow 56 Section 6 Layer Implementation of emBetter lids 1s hh SOS ERLE oo eee Wee eee 63 Modem Communication ic cs core en kes occeee ces eee eeees 6
118. t S const S const S OK in numeric mode Figure 6 1 The Modem Initialization Strings The several portions of the strings are also defined for each modem in set _modem h of which a selection is depicted in Figure 6 2 The Modem AT Commands ifdef MODEM_ZYXZEL constants of the AT Command Set ordered by MACRO define AT AT define DIAL_TONE DT define DIAL PULSE DP define ERR_CTL define FACTSET define FLOW _CTL define SPK_TIME define HUP_CMD define IGNOREDIAL S define MOD_EOL Nnr Namne First command of every string Dial using Pulse dial depending on local dialing standard Dial using Tone dial depending on local dialing standard 42 42bis error control Load Factory settings Hardware CTS RTS flow control Speaker on until Carrier Detect DTR OFF causes the modem to hang up ignore dial tone important when using a telephone exchange End of line command Figure 6 2 The Modem AT Commands 6 2 3 Non blocking Modem Driver es eS 7 eS Normally the modem communication is realized in a blocking way by sending a string to the modem and waiting for the answer However in the embedded environment the microcontroller would not be available for other tasks which is not allowed Therefore the state machine of the DRM049 Rev 0 Designer Reference Manual MOTOROLA Layer Implementation o
119. ter 69 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Table 6 2 physical c Functions Functions called Variaples Function name Return value Parameters accessed Description phy_callback void void sci_setCallback pCBackHigherL Sets physical status cPhyStatus to PHY_UP and redirects SCI ISR to upper layer phy_close void void modem_close cPhyStatus Closes the physical layer phy_init UINT8 CallbackFunc modem_init cPhyStatus Initializes the phy_callback physical layer calls pCBackHigherL modem initialization phy_open UINT8 void phy_init cPhyStatus Opens a modem_open net_errno connection sci_setCallback pCBackHigherL redirects SCI ISR to upper layer after completion phy_write void UINT8 sci_sendChar Writes a character via the SCI to the remote host Designer Reference Manual DRM049 Rev 0 70 Layer Implementation of emBetter For More Information On This Product Go to www freescale com MOTOROLA Freescale Semiconductor Inc Layer Implementation of emBetter Modem Communication Table 6 3 drv_modem c Functions Functions Variables Function name Return value Parameters called accessed Description modem_close void void modem_hangUp cModStatus Closes the modem modem_dial void void tot_delay DiallSP calls the ISP modem_write modem_hangUp void void tot_
120. the same protocol type If there is no match or if the system is not able to accept a new connection on the called port the datagram is silently discarded For details see the soc_handler procedure in socket c In case of a match the handler of the specified protocol is being called For the different processing of TCP segments see chapter6 6 5 and UDP segments see 6 6 4 User Datagram Protocol Designer Reference Manual DRM049 Rev 0 86 Layer Implementation of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Socket Interface 6 6 4 User Datagram Protocol 6 6 4 1 Overview The UDP protocol is implemented in socket c and provides connectionless unreliable data transmission UDP is a very easy protocol which requires only marginal system resources Therefore it may be used for basic functionality and for network administration applications 6 6 4 2 Receiving UDP segments udp_handler retrieves an st_buf element and stores the sender address and the data in this st_ buf element Then the in buffer element is associated to the socket through setting the value cDataIn in the socket element to the index of the st_buf element Furthermore the st_buf x cSock variable points to the socket using that buffer This redundancy of references helps to reduce overhead in finding a socket related to a specific buffer and vice versa
121. tion of emBetter MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Layer Implementation of emBetter Hypertext Transfer Protocol The last file entry r n r n in the example must always be present to allow the server to send the HTTP error 404 file not found In the case that a requested file cannot be found the server only finds the end of the header that is defined with r n r n The connected client is notified of the error with the common error page 404_ html The example shows that two filenames can be mapped to a same file The files index html and are both mapped to index_html Ona browser requesting the default file by sending GET HTTP 1 1 the index page is being sent 6 7 3 Receiving Data Through the POST Method DRM049 Rev 0 As shown in Figure 6 20 Function Template for Generating Dynamic Content a POST method consist of two strings that need to be examined e the filename of the originating file e astring with field names and values The HTTP server has to parse for the filename before exploiting the variables Furthermore the end condition of the POST object is the string Refresh that indicates that the originating file should be transmitted There can be more than one end condition string specified in ppost_refresh It must be assured that the correct number of end conditions is defined in HTTP_NUM_REFR In the example im
122. uf array of struct sNet_buf contains of incoming data for an application TCP segments to send Another buffer is defined as udOut Buf in buffer c It might lead to confusion that this variable is called buffer since it only contains of information about the memory locations of different parts of data to transmit It is explained in more detail below The data communication interface is the serial port of the HC12 The serial port provides an interrupt source for incoming characters This function is exploited by the function ppp receive in module ppp c The aim of this function is to form frames in the memory variable PPPbuffer NET_INDATA SIZE of the incoming byte stream The maximum size of this buffer is NET_INDATA SIZE and is defined in netGlobal h Designer Reference Manual MOTOROLA Overall Implementation of emBetter 57 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Overall Implementation of emBetter After a complete frame is received the status variable cPPPStatus is set to IS_FRAME As long as a frame is present in the buffer any incoming characters are discarded The function ppp _entry polls the flag IS FRAME and invokes a chain of function calls ppp_entry ip_handler ppp_handlelPCP soc_handle handlePAP Ppp_ icmp_handler udp_handler ppp_handleLCP tcp_handler Figure 5 7 Call Structure of Function ppp_entry The diamonds represente
123. uildHeader ppp_write Figure 6 15 Function Calls Caused by soc_write The socket variable provides the values in Table 6 3 drv_modem c Functions for both the TCP header and the IP header Table 6 7 Socket Values for TCP and IP Header Socket variable Field Description stSocket sk num pTCPh gt source Source port number stSocket sk dport pTCPh gt dest Destination port number stSocket lAck pTCP gt sTCPh seq The current expected acknowledge number is the actual sequence number stSocket sk daddr stIP_out_header daddr Destination IP address After ip buildHeader is called TCP may access the following fields of the IP header that forms the TCP pseudo header to compute the checksum e Source IP address e Destination IP address e Protocol identifier e TCP length After passing the data to the data link layer the TCP segment remains in the st_buf element until it is being acknowledged The TCP socket Designer Reference Manual DRM049 Rev 0 94 Layer Implementation of emBetter For More Information On This Product Go to www freescale com MOTOROLA Freescale Semiconductor Inc Layer Implementation of emBetter Socket Interface keeps the index number of the net buffer element in the variable stSocket cDataOut The out buffers are statically connected to the socket to give preferential treatment to established connectio
124. unction icmp handler replies immediately to echo requests Incoming segments are handled differently in UDP and TCP see also 6 5 The Internet Control Message Protocol ICMP Since data is not passed to an application immediately it has to be latched This is done in the buffers in the structure st_buf SOC_NUM_BUF The constant SOC_NUM_BUF can be modified in the file netGlobal h As a default it is defined as twice the number of sockets This perceives that the project is mainly based on TCP communication For TCP one buffer for incoming data and one buffer for outgoing data per socket is favorable When emBetter is used for a UDP project the number of buffer might be set independently In order to keep memory usage low and the protection of one protocol overwriting another protocols data and header each protocol has to provide memory space for its own header instead of writing to acommon memory space where outgoing data is being written to from each protocol As discussed in 4 1 Overview a set of function is provided in buffer c see Table 5 3 Overview of Functions in buffer c The set of information for an outgoing packet is stored in the struct udOutBuf BUF_MAX CNT where BUF MAX CNT defines the maximum number of parallel outbuffers Building multiple packets at a time allows for example the parallel sending of a TCP packet and answering to an echo request Table 5 3 Overview of Functions in buffer c Fun
125. v 0 IP starts to exploit the header of the incoming datagram as soon as the function ip handler is being called The datagrams is checked for formal requirements If it does not meet the requirements it is being discarded by returning back to the calling function that is ppp_entry When the formal requirements are met the handler of the protocol according to the protocol identifier in the IP header is called UDP and TCP segments are both treated in the function soc_handler ICMP datagrams are replied using the icmp_handler The formal requirements that are checked within ip handler are e Version 4 IP datagram e No options header length 20 bytes e Destination address of the IP datagram equals the IP address assigned to the local adapter e Datagrams must not be fragmented Three values out of the IP header are needed for further processing and are put on the stack of this function e source IP address e data length e protocol identifier The function to send an IP datagram is called ip write This function is called by upper layer protocols such as TCP which encapsulate data and headers in an IP datagram As the Internet Protocol is connectionless the upper layers have to provide the complete parameter set destination ip address Buffer handle calling function for every new packet The IP header is built and stored in the appropriate place in udOut Buf as described in 5 4 3 Outgoing Data Designer Refere

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