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Chapter 4: The C programming environment for the 8051

1. testl c ver03 12 blink LED of the 8051RL sbc computer compile line gt sdcc code loc 0x8000 main return test1 c int i a temp xdata unsigned char p8255_cnt 0xe003 xdata unsigned char p8255_p0 0xe000 main ANIT 8255 p8255_cnt 0x839 set 8255 control word portA out for G 0 i lt 10 i for a 0 a lt 100000 a p8255_p0 0x0f set OxOf as output pattern at portA for a 0 a lt 100000 a p8255_p0 0xf0 set OxOf as output pattern portA Now you will have a set of output files Testl asm assembly program test ihx executable 8051 Intel hex file format etc 4 11 Installation of Paulmon2 on the 8051 board You need to download the paulmon2 object file from the Internet Object code as well as source code can be found at http www pjrc com tech 805 1 paulmon2 html In order to use Paulmon2 with SDCC the interrupt vectors needed to be redirected to the 8000H region The procedures will be explained in the laboratory session The documentation of this software is at http www pjrc com tech 8051 pm2_docs index html Mobile Robot chapter 4 C and 8051 v4 a 4 12 Paulmon2 basic commands By using Windows Hyper terminal you can communicate with the SBC using the Paulmon2 monitor with the following commands See http www pjrc com tech 8051 pm2_docs commands html for details Help M List programs R Run program D Download U Upload N
2. List the code in the SBC memory space onto the screen of the PC You may view the code in hex format or dis assemble format it has a dis assembler to turn the object code in memory to assembly language e Jump to the starting address at any program starting locating as the user wishes 2 So the development cycle is as follows e At the PC the programmer can write his program using an editor and compile the C source with a compiler such as the SDCC The output of the compiler can be an object file in the Intel hex format e Use the download command of the monitor program to transfer the object code from the PC to the data program RAM space say 8000H if this space is common to data and program the monitor program can place the object code received to the space as if they are data e From the PC hyper terminal issue a run command to execute the code from the address location of the testing program The advantage of using this monitor program approach is that there is no extra hardware needed you only need a SBC a serial cable and a PC 4 5 The free C compiler SDCC http sdcc sourceforge net The public domain C compiler SDCC 3 translates your C language program into 8051 object code then uses the public domain Paulmon2 monitor program resides in the EPROM of the 8051 to deliver the object code into the target 8051 board Finally after a run command is issued to the Pulmon2 monitor your experimental code will be runni
3. down The requirement is that the system has a flash memory and has the flash programming capability 4 3 The software development systems 1 Paulmon 4 A monitor program in the ROM of the SBC board 2 SDCC A C cross compiler for the 8051 the word cross means you are using an 80x86 processor of your PC to compile your source to become not 80x86 code but 8051 code 8031 SBC Step4 use run command of Paulmon2 to run code from 8000H SRAM space oc Step2 Use Step 1 EPROM space HyperTer Use SDCC for Paulmon2 minal talk from 0000H PC windows running HyperTerminal cross compiler wae to generate a Paulmon2 803 1 object Step3 use code RS232 for downloading program to SRAM Figure 4 5 To show relations of the sofware systems used and the steps of the monitor development method 4 4 Paulmon The monitor program based development system Paulmon is a monitor program or a simple operating system which has the following functions 1 Start the SBC computer and its serial interface with the PC which may use terminal emulator software i e Hyper terminal in Windows for the communication By Mobile Robot chapter 4 C and 8051 v4 a using this serial link the user can use a number of commands from the keyboard of the PC to instruct the SBC to execute certain functions Which includes e Responsible for downloading object codes from the PC to the 8051SBC e
4. the same as above xercise 4 2 Can you build a compiler at your SBC and develop your code solely on the f SBC only just like a PC Answer Basically yes but since the SBC has little computation power and has no mass torage hard disk or floppy disk for storing programs it is not easy to have it in reality So the following is the solution e The trick we used here is Since your SBC has a serial port and connects to the host PC you can utilize your PC to store programs and do the compilation After the object code is produced you can transfer it to the SBC to run it To use this scheme you need two things 1 a program on the SBC to communicate with the host computer 2 a RAM space to store the object code and use the monitor program to run this object code from In the last chapter we discussed that the address space of 8000H is dedicated for this function The monitor program we used is also a public domain program called Paulmon2 which will be discussed below Mobile Robot chapter 4 C and 8051 v4 a RS232 8031 SBC Step1 PC generate object Step3 long code jump to the RAM space serial link to B download RAM at program to 8000H RAM Figure 4 4 Steps of monitor based development 5 Flash based monitor program approach which is similar to a monitor program approach but the memory is stored in a flash memory rather than RAM The advantage is the program can be retained even after power
5. For example after installing the Grimson editor you can set up the macro and hot key from the menu bar open the Tools gt Configure user tools for invoking the SDCC compiler So that after you edited the program you can compile it by pressing Ctrl 5 Preferences Categories Word Wrap a User Tools Remove Fonts Empty Ctrl 4 Ea cd Colors F Print Optior Empty Ctrl 6 File lt gt Associatior ee Menutex sdcc Syntax Filters Command c sdcc binisdec exe l Tools Arqument FileName h User Tools Initial dir FileDi Macros Hotkev nia v Use shortfilename 8 3 v Capture output Save before execute 4 9 Running SDCC 1 2 3 Change directory using the command cd to a working directory for your C development system from the prompt enter the command Sdcc code loc 0x8000 main return test1 c Option description main return will add ret to the code if you call this program from a 8051 monitor program you need it to return to the monitor For Paulmon 2 when it jumps to a program in RAM use command j 8000 it will put 0000 to the stack so if it has ret it will go back to Paulmon2 after this testl c program is executed in the 8051 sbc computer Mobile Robot chapter 4 C and 8051 v4 a 4 The complete manual for SDCC and the use of its compile options can be found at C sdcc doc after installation 4 10 The testing program test1 c
6. Mobile Robot chapter 4 C and 8051 v4 a 4 1 Chapter 4 The C programming environment for the 8051 Objectives Learn about how to develop a micro controller based embedded system Learn to use a monitor program PAULMON for our 8051 system Lear to use a C compiler to develop application programs for our 8051 system Introduction In this chapter we introduce methods for developing micro controller based or embedded systems Then we will discuss how to setup a C programming environment for the micro controller 8051 Why do we need to have a C programming environment for our robot development work Of course we need a programming language but can we use assembly language or even BASIC Actually I tried both and gave me headache that still aches today Assembly is fast to run but very difficult to use you need to be a half genius to use it efficiently If your work is simple it may be an ideal choice but as your program grows larger it will become difficult to trace debug and to read too Since we are about to develop intelligence robots not dump washing machines the assembly language option is out of the question I also used BASIC52 before which is a public domain monitor program produced but not supported by Intel a sort of computer orphan But it also gave me a bad experience because it doesn t support symbolic subroutine calling That means you cannot label an inst
7. New location H Hex dump memory I Hex dump internal memory E Editing external ram C Clear memory 4 13 Connecting the 8051 SBC and the PC Download program from PC to the 8051 SBC Connect 8051 sbc to com2 or com1 using an RS232 serial cable Run Windows program accessories communication Hyper terminal Set 9600 N 8 1 com2 etc com1 or com depends Press reset at the 805 1 sbc You will see the message of Paulmon2 message on the screen Press to see the available commands D for download Now you are back to Windows Hyper terminal select transmit ASCII for sending test 1 ihx You will see series of dots then get a message of download complete Since the code is actually in 0x8000 so you can read the code or assembly disassembled by Paulmon 2 I think try N 8000 then L for viewing assembly code or H for viewing hex code Use j 8000 to jump to the start address of the executable code test1 ihx you just downloaded The LED of the 8051 sbe should blink and after a few seconds when the program terminates Paulmon 2 goes back to its starting point again Done Mobile Robot chapter 4 C and 8051 v4 a 4 14 Conclusion Various embedded system development techniques have been studied In particular the way of how to setup a low cost 8051 monitor based C development has been described Experiments for students to get familiar with such a system h
8. ave been designed and discussed in this chapter 4 15 References 1 Official home of SDCC is at http sdcc sourceforge net 2 CYGWIN is at http sources redhat com cygwin 3 SDCC http sdcc sourceforge net 4 Paulmon2 user manual http www pjrc com tech 805 1 pm2_docs commands html End of this chapter Mobile Robot chapter 4 C and 8051 v4 a 10
9. ng So the required public domain tools have been discussed We will then describe the installation procedures of the software and give a number of experiments for testing our system If you are using the Windows binary version of the SDCC skip the following section 4 6 Optional Installation of CYGWIN You may need this tool if you prefer to use the Linux version of the SDCC than you should install the CYGWIN however if you prefer to use the Windows binary version of the SDCC you can skip this chapter All the links can be found at the course web page under http www cse cuhk edu hk ceg3430 CYGWIN a public domain CYGWIN interface to Windows for GNU software I believe it is an emulator to make a Windows look like a LINUX machine Installation of CYGWIN Mobile Robot chapter 4 C and 8051 v4 a 4 7 1 Download from http sources redhat com cygwin 2 Follow the instruction for installation Installation of SDCC save you US 2000 a bit exaggerating confess But by saying that it should make you happier am sure 48 1 Download SDCC from http sdcc sourceforge net 2 Follow the installation instruction 3 See the course web page for more recent information Installation of an program editor There are many public domain C program editors and one of those is the Crimson editor downloadable from www download com which has some MACROS to link up the SDCC compiler and edited program
10. r connected to the SBC depending on a set of switches When it is connected to the PC the PC saves programs to the RAM then the PC signals the switches to switch over to the SBC side and the SBC can read programs from the RAM as if it is a ROM It is a good method and cost effective too However it still needs some extra hardware the EPROM emulator Another disadvantage is that during testing the system is immobile since it has to be connected to the EPROM emulator with a lot of wires Such restriction is highly undesirable for our mobile robot development for obvious reason Step1 switch SRAM to PC Step3 In the 8051 Step3 Switch re SBC execute SRAM to SBC Step1 compiles program in program l RAM by O O generates object pressing reset if B AT code and saves in SRAM RAM is at 0000 onwards SRAM e g 62256 Figure 4 3 The EPROM emulator works PC controls EPROM switch xercise 4 1 Show how to use an EPROM emulator to write program and run on our SBC 4 Monitor program approach which is the method we will be using The code development procedure you normally used for a PC is as follows e You first boot up your computer in Windows or something else if you don t want to associate yourself with Bill e Then you start a compiler edit your program and then run your executable code from the file with a file extension of exe within the Windows environment How about our SBC development cycle is it
11. ruction by a symbol you can only call a subprogram by its location number structural programming becomes very difficult to write So I determined to use C So what kind of C compilers will we use Keil C http www keil com home htm is undoubtedly the industrial standard for its maturity and user friendliness Since our lab has a license so I am quite happy to use it But when I consider using it for my course of 50 students the price tag of US1600 for each license really puts me off Then I turned to the web and look for low cost or even free C compilers for our experiments With a bit of luck a Free C cross compiler called SDCC is found I tested it and it works ok for our experiments In the following sections we will first describe the way an embedded system is developed Then we will concentrate on the public domain C programming environment we selected and demonstrate to you how to use it for our work Mobile Robot chapter 4 C and 8051 v4 a 4 2 Embedded system Development procedures A standalone small computer system namely an embedded system usually consists of a micro controller a ROM for holding the software and a RAM for storing variables To develop programs for such a system you have a number of choices 1 In circuit emulator It is a rather expensive solution and is usually hocked up to a PC as host You can write your C program compile it then download the output object code to the emulator which emulates the hard
12. ware functions of a micro controller It is usually used in the hardware development stage where the hardware of a SBC is not ready yet But since the SBC hardware we used is a fully tested commercially available product and our attention is on device interfacing and programming so we will not use this method 40 pin PC and hardware Connector Use the fast 80x86 and high speed logic circuit to emulator the slow 8051 processor RAM ROM can 8051 pin8031 slot perenne Target 8031 board to be developed Figure 4 1 The use of In circuit emulator in board development 2 EPROM based development Use an assembler or a high level language compiler to write your program and translate it into object code on a PC Afterwards use an EPROM programmer to write the object file into an EPROM then insert the EPROM to the micro controller board and run the program for testing Figure 4 2 The EPROM based development procedures Step1 PC With a EPROM cross compiler to programmer to generate object write object file code for 8051 into an EPROM Step2 Produced Step3 Place the EPROM to the slot by 8051 SBC 3 EPROM emulator based approach This approach is the same as EPROM based development but use EPROM emulator hardware for rapid downloading and testing An EPROM emulator is a RAM sitting between a PC and a SBC The RAM can be Mobile Robot chapter 4 C and 8051 v4 a connected to the PC for read write o

Chapter 4: The C programming environment for the 8051

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