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Setting up Zephyr Environment Detailed description about Zephyr environment can be found here . Since most of the prerequisites are common to other development, chances are you already have most of them installed on your computer. Ubuntu and its derivative users may need to uninstall outdated device-tree-compiler package and install new one by building from the source Running a Sample Code Grab one of the board listed as supported , clone the Zephyr source tree , go to one of the sample code directory and run: Default CMake generator is "Unix Makefile". However ninja is way more faster. You can override it by creating a file named PreLoad.cmake with following content: and put it in the same directory as CMakeLists.txt. Additionally you can set the board in the CMakeLists.txt so you don't have to specify in the command line. Note that this line comes before including the boilerplate setting. Blinky We are going to use ST Disco L475 IoT01 board in this ex

There are at least two revisions of the B-L475E-IOT0A board. Earlier boards (version C) have rather critical bug in the hardware, so the STLink-V2 does not work. This is because the NRST net between STLink and the main MCU is missing in the version C board. For more information, check the manual . Unfortunately the manual didn't describe how to fix it, although it is rather straightforward. Grab a soldering tools and connect two points shown below. On the schematic these two points correspond to and Now, you should be able to run the hello_world example without problem.

Build a low level driver for SD card, then the glue logic for FatFs and USB MSD is pretty much the same as Flash memory case posed before. In case of SD card, sector size is 512 in most of the cases. Thus the memory requirement is much relaxed. You can even allocate a file buffer that is bigger than the sector size. FatFs site has a  dedicated page for MMC/SDC, on which you can find fairly detailed explanation about how to interface MMC/SDC via SPI bus. Implementation should be straightforward until you encounter with cheap SD cards that do not behave very well. In such cases, you either have to protect your code with redundancy or just stick with quality devices. If you choose SanDisk or Kingston brand, you will be safe. ADATA on the other hand, frequently generates timeout error at first try. Most of the SD card sockets have a pin to detect the presence of the card. This pin is usually connected to GND pin or some other pin. You can use this to generate interrupt whenever a ca

Most of the development kits from ST are equipped with on-board STLink-V2 debugger / programmers, use of which is not very convenient in Linux environment. Instead, Segger kindly provides a tool that allows you to reflash on-board STLink into JLink . Process takes only seconds. And you can enjoy most of the great features of JLink with no cost at least for STM32 devices. It keeps the UART port function, so you can use it as a serial monitor in addition to the JLink. If you have a Nucleo-64 board handy, you can make a nice stand-alone JLink debugger by reflashing the on-board STLink and snap it off. Note that the original pin headers are removed and some of them are replaced with right-angle type for the convenience. Two of the pins of ST-Link jumper are used to provide 3.3V power. And TX and RX pins of UART are soldered at the back not to interfere with the debug pins. Note the small changes in the solder bridges SB3 through SB10. Basically this allows the 3V3 line to b

STM32Cube framework provides very similar interface for FatFS as USB MSC we have seen before. Again the same argument applies to this case about the basic unit of read/write operation on a flash memory. In this case, the sector size and the cluster size should be equal to the sector size of flash memory, namely 4KB. This can be set in the file ffconf.h , in which a lot of customization can be done by changing the definitions. In particular, following definitions should be set. In the file user_diskio.c, USER_read and USER_write functions can be implemented as the same way as before. Here we assume that the count is always one for the simplicity. In reality this can be bigger than one if you call f_read() with the buffer size larger than the sector size (4096). However given the limited memory capacity, that is not realistic. By similar token, pdrv variable can be ignored. If ioctl is to be used, then  FatFs allows users to not only read and write files but also to crea

USB Mass Storage Class framework implements bulk-only-transfer (BOT) with SCSI protocol. USB packets from the host eventually converted SCSI transport commands by the middleware, in which data is exchanged (read / write) in the unit of logical block, typically 512 bytes. This SCSI commands works well with SD card system where a dedicated controller does the job of managing the actual memory elements. If you want to use a FLASH chip as a memory unit instead, you need to handle read / write operation directly. Fortunately, most of flash memory support 4KB block erase. This makes the 4096 bytes as a natural choice for the size of the logical block in the file usbd_storage_if.c. In this case, 8Mbit Flash memory was used. During initial enumeration, this information is registered to the host. The middleware maintains one logical block size of buffer and handles USB transaction where each payload is only 64 bytes. It then calls SCSI requests to store / retrieve data to / from physical