Bachelor Thesis Electrical Engineering November
Contents
1. Operating System Dynamic Link Library A free software mass collaboration project Git repository web based hosting service Graphical User Interface A family of instruction set architectures for computer pro cessors GNU Compiler Collection A software collaboration platform First In First Out Receive receiver or reception Transmit transmitter or transmission Virtual COM Port Light emitting diode Megabits per second coca vi Contents 1 2 Introduction Background 2 1 Host and device roles 2 2 Communication and transfer types 2 3 Hardware 2 4 STM USB Library 2 5 Libusb and libusb win32 Setting up the working environment 3 1 Accessing the USB driver ona PC 3 2 Usefultools 0 3 3 Installing and configuring CooCox CoIDE 3 4 Using Code Blocks to link the libusb win32 library USB FS 4 1 First test using a Virtual Communications Port VCP example 4 2 Writing tothe board 4 3 Reading from the board USB HS 5 1 Troubleshooting and future suggestions Conclusion Appendix 11 11 12 13 vii 1 Introduction The main requirement of this project was to establish a High Speed USB 2 0 communication between the board provided by Baltic Engineering AB and a PC using C programming skills The work was carried out by researching how the USB communication works and investig2. between 0 and 15 and a direction IN or OUT The direction is determined from the host s perspective i e IN from device to host OUT from host to device Endpoint 0 is set as a control endpoint More information about the endpoints can be found on the book USB Complete 1 p 34 35 Descriptors Descriptors are data structures that describe the peripheral There are many descriptor types but the essential ones for most implementa tions are in the hierarchical order device configuration interface endpoint String descriptor is optional but can be useful It can contain descriptive text to provide more information about the device Strings are encoded in Unicode and can support different languages More information about the desriptors can be found in the book 1 Ch 4 or this website 2 2 3 Hardware The microcontroller used in this thesis work is STM32F405 which belongs to STM32xx family manufactured by ST Microelectronics It is based on the high performance ARM Cortex M4 32 bit RISC core operating at a frequency up to 168MHz The STM32F405xx include an USB OTG full speed device host OTG peripheral with integrated transceivers 3 p 12 For HS communication an external USB controller is needed connected to ULPI in this case a USB3300 chip The STM32F405 is used in a custom board that has two physical USB ports One is connected directly to the microcontroller and supports full speed communication 12 MB s The other po
3. read Therefore the host can perform the reading operation with the usb_bulk_read function Peripheral side Since vendor specific requests are used the device has to be able to interpret them Hence an extra rule is added in USBD_SetupStage function located in usbd_core c The rule captures the packets with the right bmRequestType field and uses a callback to redirect it to usbd_cdc_Setup function found in custom c Here the packet s bRequest value is checked and the further operations are performed There were two configurations used for testing e The function was modified to prepare a buffer with limited size During the test the buffer was filled with a sequence of numbers to be sent The test was successful and all numbers were received correctly on the PC e The function was modified to prepare the buffer to be sent many times infinitely This was used for benchmarking The PC performed the bulk read multiple times The time of all those operations was calculated as well as the number of bytes read Finally the data rate was calculated and the result was around 2 Mbps Important note One of the common uses of USB transfers is to send and receive data that has a certain size In that case a setup packet should be sent with wLength parameter that indicates the number of bytes to transfer during the data phase After receiving that kind of control message the peripheral should have a mechanism implemented to keep prepar
4. s requirements trou bleshooting and suggestions 2 Background Many electronic devices nowadays support Universal Serial Bus USB USB is known as an industry standard for short distance digital data communication in our case between a laptop and the electronic circuit provided by Baltic En gineering AB The key difference between the USB HS and the USB FS mode is the data transfer speed USB FS is transferring data at 12 Mbps while the USB HS is transferring at 480 Mbps USB On The Go OTG is an extension of the USB 2 0 specification It is a dual role device that can act both as a host and as a peripheral for example mouse memory stick or custom made hardware 2 1 Host and device roles In order for the USB communication to be established there must be a host and a peripheral A host is usually defined as a computer which controls the interface It initiates a communication session and the peripheral must wait and respond Moreover it has to know each of the devices that are attached to it and their capabilities The host deals with devices that have different requirements and ensures that all the devices attached have the possibility to send and receive data at the same time To make sure that data is sent and received without errors the host adds error checking bits The host takes care of a process called enumeration and provides the devices with power During enumeration the host assigns an address to the device and request addit
5. them iv Abstract The goal of this thesis work is to test the High Speed USB 2 0 communication between a custom board and a PC Baltic Engineering AB has developed a hardware platform based on a microcontroller from ST microelectronics The microcontroller STM32F405 is equipped with many peripheral functions one of which is a High Speed USB 2 0 OTG unit Baltic Engineering AB is planning to use this function in future projects but at the moment they have no experience of implementing software code for this type of communication link The work is focused on programming and establishing the connection be tween the PC and the microcontroller It is explained how to set up the de velopment environment with CooCox CoIDE and how to write programs in C programming language with the help of the libusb library The outcome of the project was a successful establishment of the USB FS communication Furthermore a bulk transfer was benchmarked and reached the bandwidth of approximately 2 Mb s Glossary ARM GCC Launchpad FIFO Rx Tx VCP LED Mbps niversal Serial Bus SB Full Speed SB High Speed JSB On The Go Reduced Instruction Set Computing USB 2 0 Transceiver Macrocell Interface UTMI Low Pin Interface Physical Layer Device or Protocol Personal Computer STMicroelectronics Device Core Driver Identification Integrated development environment A generic USB driver provided by Microsoft Berkeley Software Distribution
6. Bachelor Thesis Electrical Engineering November 2014 USB COMMUNICATION ON STM32F405 DONATAS KATEIVA ERAY DURAN Department of Applied Signal Processing Blekinge Institute of Technology 37179 Karlskrona Sweden External Advisors Gerth Fohlin Baltic Engineering AB Anders Bengtsson Baltic Engineering AB University examiners Sven Johansson University advisors Johan Zackrisson Department of Applied Signal Processing Blekinge Institute of Technology 371 79 KARLSKRONA SWEDEN Internet www bth se tisb Phone 46 455 385000 SWEDEN Declaration This thesis work was carried out at Blekinge Institute of Technology BTH Sweden in collaboration with Baltic Engineering AB All the external informa tion used for the completion of this thesis work is given as a reference Acknowledgements As authors we are thankful to our supervisor Sven Johansson who permitted us to start working on this thesis topic and made all the necessary administra tion processes with Baltic Engineering AB and BTH We would like to express our gratitude to our supervisor Johan Zackrisson for his support and guidance throughout our thesis work We are grateful that he has been extremely en thusiastic and that he shared all his knowledge and gave his best whenever we needed some help Last but not least we would like to express our thanks to Gerth Fohlin and Anders Bengtsson from Baltic Engineering AB for giving us the opportunity to work with
7. PI Furthermore the desired mode is selected since USB OTG HS core supports both FS and HS modes Finally the pin assignment has to be changed in usb_bsp c to match the microcontrollers connections to the USB3300 chip To test the setup with these changes the code was compiled and loaded to the board The USB connection between the PC and the board was not recognized There was no response 5 1 Troubleshooting and future suggestions Low Power Mode Some forums about the HS implementation on STM32F4 showed that other people with similar problems were having issues with LPM low power mode 20 To test this suggestion LPM was explicitly disabled in usb_core c by writing to the register GUSBCFG bit 15 PHYLPCS 21 p1389 1391 Still the device was not detected on host OS Checking the clock One of the troubleshooting ideas was to check the hard ware clocks and supplies After using the oscilloscope it was possible to verify the functioning of the USB FS clock but not the USB HS clock Suggestions for future troubleshooting According to one user in a post on the ST forum the crystal won t oscillate if the chip is held on reset 20 One possibility could be to use the oscilloscope to check the status of the reset pin as well as the X3 clock If the clock is not oscillating and the reset is on try to find a way to turn it off 11 6 Conclusion This work shows you how to set up a development environment on a Win dows PC for prog
8. This method provides the highest throughput and is used when the time is not critical A typical example for a bulk transfer is sending some data to a printer The Bulk Transfers are used to reach the maximum speed for our communication Bulk Transfer is very fast when the bus is idle however the data can be delayed when there are other transfers with higher priority Bulk transfer provides error detection and re transmission mechanisms e Interrupt transfers are requests that need immediate action Typical ex amples are keyboards and game controllers Those types of transfers have limited bandwidth at low and full speed but high speed enables an inter rupt endpoint to transfer almost 400 times more data than full speed e Isochronous transfers occur continuously or periodically and are used for data that needs a guaranteed on time delivery rate This is the only trans fer type with no data re transmission or error detection but guarantees constant bit rate transfers More information about the transfer types can be found in the book USB Com plete 1 Ch 3 In this work data integrity is crucial and data needs to be transmitted with out errors Therefore bulk type transfers were used Endpoints In USB devices the endpoint is used for data transfers It is a buffer that typically stores multiple bytes and consists of a block of data memory or a register in the device controller chip 1 p 34 35 Each endpoint has an address a value
9. asy access to USB devices on many different operating systems T Libusb win32 is an open source libusb project for the Windows operating system 8 It supports all types of USB transfers Control Bulk Isochronous and Interrupt as well as all standard device requests The control transfers support sending both standard requests and vendor specific messages 3 Setting up the working environment The operating system used in the project is Windows 8 1 The working environment consists of two IDEs CooCox CoIDE 9 and Code Blocks 10 The former has been chosen because it is used by Baltic Engineering AB for the development of their products It is used for the microcontroller development The latter has been chosen for coding for the applications to be run on a PC Code Blocks uses the MinGW Minimalist GNU environment for Windows compiler It is not compulsory to use Code Blocks for this application It is possible to use any other compiler 3 1 Accessing the USB driver on a PC Creating applications for a PC to test the USB communication required a way to access the PC s USB driver On a Windows system two options were considered WinUSB and libusb win32 The libusb win32 was selected because it is based on a cross platform library that is available on multiple platforms Linux Windows Mac OS X BSDs and Android This makes it easier to port to other platforms if needed The library DLL and import lib examples installers is open
10. ath since the other option produced linking errors during the compilation 4 USB FS To use USB FS mode it is necessary to select the correct core in usb_conf h file define USE_USB_OTG_FS and enable it during the library initialization as stated in the STM USB library document 6 8 The snippet of code below is an example of how the USB FS core is initialized It is executed in the main function at the start of the program USBD_Init XUSB_OTG_dev USB_OTG_FS_CORE_ID amp USR_desc XUSBD_MY_cb amp USR_cb Furthermore it is necessary to select the desired mode device host or OTG It is done in usb_conf h file by defining one of these keywords USE_HOST_MODE USE_DEVICE_MODE or USE_OTG_MODE For example define USE_DEVICE_MODE selects the device mode After that it is necessary to configure the USB descriptors The device and string descriptors e g product and vendor IDs can be changed in usbd_desc c file In this project two files were created custom c and custom h for modifying the configuration interface and endpoint descriptors They are based on the STM USB library example files usbd_cdc_core h and usbd_cdc_core c The size of the descriptors is specified in custom h while the descriptors themselves are written inside custom c If desired the Tx and Rx FIFO size can be changed in usb_conf h file 6 88 Finally the endpoints are initialized during the start of the program by calling the DCD_EP_Open funct
11. ating possible implementations on a PC running Windows Then followed the verification and troubleshooting In the end a successful USB FS USB Full Speed 1 1 communication was established and was tested by performing read and write operations The writing was verified by sending data to the board and making one of its LEDs Light Emitting Diode blink The reading was checked by creating a sequence of numbers on the board and transferring all the data correctly on a computer However the USB HS USB High Speed 2 0 was not recognized by the PC The thesis is divided into 4 parts The first part of the report is general overview It involves the description of the USB protocol its functionality and necessary elements for the establishment of the communication It also describes the essential hardware components as well as the libraries used in this project The second part of the report is focused on explaining how to set up the working environment It contains information about downloading installing the software and the necessary drivers configuring the IDEs and linking the libraries Useful software is briefly introduced that is helpful for troubleshooting The third part is about the requirements for establishing the USB FS com munication reading and writing to and from the board It covers the program ming on both the PC and the board Only the essential parts of the coding is explained The fourth part is about the USB HS communication
12. class number of configurations interfaces endpoints ad dresses of the endpoints etc All of the information can also be obtained by using functions in the libusb library Nevertheless testlibusb win exe displays everything in a GUI and doesnt require additional programming 3 3 Installing and configuring CooCox CoIDE In order to set up CooCox CoIDE environment three things should be in stalled e CooCox CoIDE e GNU Tools for ARM Embedded Processors e ST Link V2 driver CooCox CoIDE can be downloaded from the CooCox s main website 9 The ST Link V2 driver can be obtained from the company s website 15 The GCC compiler can be downloaded from Launchpad s website 16 After downloading and installing these tools it is necessary to configure the GCC compiler and the debugger before starting a project in CooCox CoIDE There is a page on the CooCox website which has an illustrated step by step guide that explains the process 17 3 4 Using Code Blocks to link the libusb win32 library Download libusb win32 18 and extract it Create a project in Code Blocks Then copy the lusbO_usb h and libusb a files to the projects directory In clude the lusbO_usb h include lusbO_usb h and add the link library libusb a to the project go to Project gt Build Options gt Linker settings then add the a file The file can be added both as a relative or non relative path In this project the file has been added as a non relative p
13. ex_mx_stm32 2FSTM32F2F4 20problems 20with 20various 20ULPI 20USB 20PHYs amp currentviews 2865 21 RM0090 Reference manual STMicroelectronics Doc ID 018909 Rev 6 February 2014 2014 12 04 http www st com web en resource technical document reference_manual DM00031020 pdf 15
14. h is a callback to the devices core layer Result In the test USB device code is modified to process each incoming data packet and check the last byte in the buffer If the byte equals to a the board blinks one of its LEDs This test was successful and it was possible to send a packet from the PC to the board and blink an LED each time 4 3 Reading from the board In order to test the reading from the board it is necessary to firstly prepare the data that is going to be transferred This is performed by sending two custom commands to the USB controller It should be done after initialization and claiming the interface the same way as described in the beginning of section 4 2 The custom commands are not standard USB requests Therefore it is important to implement a way to handle them on both the host and the peripheral A more detailed explanation of this process will be presented from both host s and device s perspectives Host side In the beginning the host istructs the device to generate a packet of data This is done by issuing a custom command which is a control transfer with bmRequestType field set to 0xC3 and bRequest field set to 0 Then the host sends another command to tell the device to prepare the data to be sent on the IN endpoint This time it is a control message which is similar to the first one The difference is that the bRequest field is set to 1 After these two messages the data is generated and prepared to be
15. ing the buffer to be sent out on IN endpoint until there is no more data to be read For example the maximum size of the data packet in USB FS is 64 bytes If the host has to read 640 bytes of data it should firstly send a control message requesting 640 bytes of data The peripheral should prepare the first 64 bytes to be sent on the IN endpoint When the host initiates the bulk read the transfer occurs and the peripheral prepares the next 64 bytes Both continue doing this until there is no more data to exchange This way the host does not need to send a control message before each bulk read Therefore the transfer of data is faster See table 2 as an illustration of this example Host Peripheral Control read 640 bytes Prepare first 64 bytes Bulk read 64 bytes Prepare next 64 bytes Bulk read 64 bytes Prepare next 64 bytes Prepare last 64 bytes Bulk read 64 bytes Table 2 An example of host reading 640 bytes of data 10 5 USB HS To enable the HS mode it is necessary to select the correct core and initialize it similarly to the FS part see section 4 It is also required to select the mode of operation device host or OTG The physical port of the USB HS is not directly connected to the microcontroller on the board Instead it uses a ULPI interface and is connected to USB3000 chip Before the initialization it is therefore required to select the correct interface for the HS communication In this case UL
16. ion with the correct parameters In custom c two endpoints are opened one for sending data EP IN and one for receiving EP OUT See the example below Open EP IN DCD_EP_Open pdev CDC_IN_EP CDC_DATA_IN_PACKET_SIZE USB_OTG_EP_BULK Open EP OUT DCD_EP_Open pdev CDC_OUT_EP CDC_DATA_OUT_PACKET_SIZE USB_OTG_EP_BULK 4 1 First test using a Virtual Communications Port VCP example The first test was done by using a VCP example for the STM32F4xx Discov ery Board from one of the pages on GitHub 19 After compiling and running this code the microcontroller was recognised as a virtual COM port It was then possible to use a serial console e g PuTTY with a VCP driver the example s page has information about it to connect to the microcontroller and send or receive data In this project the example was used to verify if the board was functional It also served as a basis for the development of the custom USB driver for the microcontroller 4 2 Writing to the board For this task a small program is written for a PC based on libusb win32 library In the beginning the library is initialized with with usb_init To find a particular device all buses and devices are enumerated by using usb_find_ busses and usb_find_devices Later the program iterates through each device in each bus During this process the device descriptors of all connected devices are read The program checks the values of the Vendor ID and P
17. ional information from the device to establish the communication between each other The peripheral acts as a slave in the USB communication Like the host the peripheral adds error checking bits when it transmits data and makes error checking calculation when data is received If it detects that there is some error in the transmission it informs the host to retransmit the data 2 2 Communication and transfer types Typically USB communication is divided into two types configuration com munications and application communications During configuration communi cation or enumeration the peripheral identifies and responds to control requests from the host After the enumeration process is done the application phase fol lows where the application specific communication can start The USB standard describes four basic types of communication control bulk interrupt and isochronous e Control transfers have two main uses One is carrying the standard re quests that are used to learn about and configure devices The other is transferring the custom requests defined by a vendor or class All devices must support control transfers over the endpoint zero There is a portion of the bus bandwidth reserved for control messages 10 for low and full speed and 20 for high speed and SuperSpeed buses This ensures that the control transfers are performed as fast as possible e Bulk transfers are used to transfer large and bursty types of data
18. ramming the STM32F4 microcontroller and using its USB functionality It explains how to write programs in C language to transfer data between the PC and the microcontroller with the help of libusb library In the end a successful USB FS 1 1 communication was established It was possible to send and receive the data from the microcontroller The communi cation was benchmarked and reached the throughput of approximately 2 Mb s The establishment of USB HS 2 0 was not successful Nevertheless the re quirements to enable it are explained in the document as well as the ideas for further troubleshooting 12 7 Appendix Explanation of the USB HS The first function in main is SystemInit Later follows the ledinit function from the myledcontrol h file which has been created to initialize and give an easy control of the LEDs Then init function initializes SysTick and USB USBD_Init calls the function USB_OTG_BSP_Init that initializes the board specific configurations from usb_bsp c takes care of the user callbacks and the specified core in this case HS One of the callbacks is structure USBD_Class_cb_TypeDef This structure gives access to the class driver and is used inside the custom c to create the functions that are required to control the USB device e g initialization setup and data in out stages sending the configuration descriptor The board specific initialization is handled by USB_OTG_BSP_Init func tion In thi
19. roduct ID If they both match the usb_dev_handle is retrieved the device is opened with the function usb_open Later the preferred configuration is selected with usb_set_configuration Sometimes a peripheral can be programmed to have multiple configurations e g one when it is bus powered and another when it is powered by a different source Finally the interface is claimed with usb_claim_interface After all of these steps the writing operation can be started To perform a bulk OUT transfer the endpoint should be prepared to receive the data Therefore usb_control_msg is called It sends a setup packet with a set of parameters One of the parameters is bmRequestType It is a number that has a length of 1 byte The fields of the parameter are specified in the table 1 More information about the setup stage can be found on 1 5 Bit What is specified Direction 0 host to device 1 device to host Type 0 standard 1 class 2 vendor 3 reserved Recipient 0 device 1 interface 2 endpoint 3 other BON 5 in Table 1 bmRequestType parameter In this case bmRequestType determines these options type vendor direc tion device to host After this packet is sent the USB device prepares the OUT endpoint to receive data Then usb_bulk_write is called and the host sends 64 bytes of data On the board side the received data is processed in custom c file usbd_cdc_ DataOut function whic
20. rt is attached to the USB3300 chip According to its datasheet 4 the USB3300 is an industrial temperature Hi Speed USB Physical Layer Transceiver PHY It uses ULPI low pin count interface The USB3300 PHY can work in device host and OTG modes In order to write a program to the STM32F405 microcontroller the ST Link V2 is used which is a debugging and programming interface between the board and the PC 5 2 4 STM USB Library STM USB library offers a simplified way to program the USB devices It takes care of the low level communication and provides an interface to control the USB transfers It consists of three layers USB low level driver module USB library module and Application module 6 6 1 Most of the coding should be done in the upper layers since the library provides the configuration files and the callbacks of the functions to the low lever driver Using the library it is possible to implement classes that conform to the specification of the protocol 6 6 7 A custom class also called vendor specific class can be added by using the USBD_Class_cb_TypeDef 6 6 5 structure that provides callbacks for different events such as initialization de initialization setup data in out and etc When these callbacks are called the transfers can be managed by using Device Core Driver DCD layers functions found in usb_dcd h and usb_dcd c files 2 5 Libusb and libusb win32 Libusb is a C library that gives applications e
21. s configuration low power mode is disabled USB HS core is selected and ULPI mode is chosen The pin assignment is adjusted to match the custom board connections with the USB3300 chip In the beginning of the selected configuration AHB1 clock is enabled for the ULPI pins Then each pin has a function mapped to it according to the schematic Later the parameters of each pin are changed through GPIO_InitStructure and initialized Further more RCC_AHB1PeriphClockCmd function enables the AHB1 clocks for HS and ULPI Finally the PWR clock is enabled 13 References 1 2 3 a 10 11 12 13 14 1 Ol 16 Jan Axelson USB Complete Fourth Edition The Developer s Guide Lake view Research 4th edition 2009 USB Descriptors 2014 10 03 http www beyondlogic org usbnutshell usb5 shtml STM82F405xz datasheet DocID022152 Rev 4 June 2013 2014 12 04 http www st com st web ui static active en resource technical document datasheet DM00037051 pdf USB33800 Hi Speed USB Host Device or OTG PHY with ULPI Low Pin Interface Rev 1 1 01 24 13 Microchip 2014 12 04 http ww1 microchip com downloads en DeviceDoc 3300 pdf ST LINK V2 datasheet Doc ID 018751 Rev 3 September 2012 2014 12 04 http www st com st web ui static active en resource technical document data_brief DM00027105 pdf STMicroelectronics UM1021 User manual Doc ID 18153 Rev 3 2014 12 04 http www st com
22. source and distributed under GNU Lesser General Public License LGPL 8 There are two ways 11 to install the driver using an INF inf file or Zadig Zadig is a Windows application that can install generic USB drivers e g WinUSB lisbusb win32 It is based on libwdi a Windows driver installer library for USB devices The installation instructions when using INF files are described in the In stallation section in libusb win32 wiki page 8 or libusb wiki This way is valid for most of the Windows versions before Windows 8 Due to the stricter rules for the installation of unsigned drivers another method has to be used on Win dows 8 An application called Zadig 12 can be used to install the generic USB drivers To install the driver download and execute Zadig select the correct USB device and install libusb win32 driver A more thorough usage guide can be found on Zadigs wiki page on GitHub 13 3 2 Useful tools USBDeview 14 is a free utility which lists the USB devices that are or had been connected to the PC It also displays information such as Vendor ID Product ID device type driver description etc The application is useful for checking if the device is recognized by the computer Also it is easy to see whether the descriptors are received correctly Testlibusb win is an executable that is included in the downloadable package from the libusb win32 website It displays information about the USB driver such as the device
23. st web ui static active en resource technical document user_manual CD00289278 pdf Libusb org wiki 2014 10 15 http www libusb org wiki WikiStart Libusb win32 wiki page 2014 10 15 http sourceforge net p libusb win32 wiki Home CooCox CoIDE 2014 10 15 http www coocox org CooCox_CoIDE htm Code Blocks 2014 10 15 http www codeblocks org Libusb org Driver Installation 2014 10 15 http www libusb org wiki windows_backend DriverInstallation Zadig main website 2014 10 15 http zadig akeo ie Zadig wiki on GitHub 2014 10 15 https github com pbatard libwdi wiki Zadig Nirsoft USBDeview 2014 10 15 http www nirsoft net utils usb_ devices_view html ST LINK V2 2014 10 16 http www st com web catalog tools FM146 CL1984 SC724 SS1677 PF251168 sc internet evalboard product 251168 jsp GCC Tools for ARM Embedded Processors 2014 10 16 https launchpad net gcc arm embedded download 14 17 18 19 20 CooCoz CoIDE Compiler Settings 2014 10 16 http www coocox org CoIDE Compiler_Settings html Libusb win32 on SourceForge 2014 10 16 http sourceforge net projects libusb win32 STM82 Discovery VCP 2014 10 16 https github com xenovacivus STM32DiscoveryVCP ST forum STM82F2 F4 problems with various ULPI USB PHYs 2014 10 16 https my st com public STe2ecommunities mcu Lists cortex_ mx_stm32 Flat aspx RootFolder 2Fpublic 2FSTe2ecommunitiess 2Fmcu 2FLists 2Fcort
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