1.. _module-pw_sys_io_baremetal_stm32f429: 2 3----------------------------- 4pw_sys_io_baremetal_stm32f429 5----------------------------- 6``pw_sys_io_baremetal_stm32f429`` implements the ``pw_sys_io`` facade over 7UART. 8 9The STM32F429 baremetal sys IO backend provides device startup code and a UART 10driver layer that allows applications built against the ``pw_sys_io`` interface 11to run on a STM32F429 chip and do simple input/output via UART. The code is 12optimized for the STM32F429I-DISC1, using USART1 (which is connected to the 13virtual COM port on the embedded ST-LINKv2 chip). However, this should work with 14all STM32F429 variations (and even some STM32F4xx chips). 15 16This backend has no configuration options. The point of it is to provide bare- 17minimum platform code needed to do UART reads/writes. 18 19Setup 20===== 21This module requires relatively minimal setup: 22 231. Write code against the ``pw_sys_io`` facade. 242. Set the backend, in a way appropriate to your build system: 25 26 * In GN, specify the ``dir_pw_sys_io_backend`` GN global variable to point to this 27 backend. 28 * In Bazel, set the ``--@pigweed//pw_sys_io:backend`` label flag to 29 ``@pigweed//pw_sys_io_baremetal_stm32f429``. Also, add the 30 ``@pigweed//pw_sys_io_baremetal_stm32f429:compatible`` constraint to 31 your platform, to indicate that the platform is compatible with 32 this backend. 33 343. Build an executable with a main() function using a toolchain that 35 supports Cortex-M4. 36 37.. note:: 38 This module provides early firmware init and a linker script, so it will 39 conflict with other modules that do any early device init or provide a linker 40 script. 41 42Module usage 43============ 44After building an executable that utilizes this backend, flash the 45produced .elf binary to the development board. Then, using a serial 46communication terminal like minicom/screen (Linux/Mac) or TeraTerm (Windows), 47connect to the device at a baud rate of 115200 (8N1). If you're not using a 48STM32F429I-DISC1 development board, manually connect a USB-to-serial TTL adapter 49to pins ``PA9`` (MCU TX) and ``PA10`` (MCU RX), making sure to match logic 50levels (e.g. 3.3V versus 1.8V). 51 52Sample connection diagram 53------------------------- 54 55.. code-block:: text 56 57 --USB Serial--+ +-----STM32F429 MCU----- 58 | | 59 TX o--->o PA10/USART1_RX 60 | | 61 RX o<---o PA9/USART1_TX 62 | | 63 --------------+ +----------------------- 64 65Dependencies 66============ 67- :ref:`module-pw_sys_io` 68- :ref:`module-pw_preprocessor` 69