1.. _module-pw_sys_io_baremetal_stm32f429:
2
3-----------------------------
4pw_sys_io_baremetal_stm32f429
5-----------------------------
6
7``pw_sys_io_baremetal_stm32f429`` implements the ``pw_sys_io`` facade over
8UART.
9
10The STM32F429 baremetal sys IO backend provides device startup code and a UART
11driver layer that allows applications built against the ``pw_sys_io`` interface
12to run on a STM32F429 chip and do simple input/output via UART. The code is
13optimized for the STM32F429I-DISC1, using USART1 (which is connected to the
14virtual COM port on the embedded ST-LINKv2 chip). However, this should work with
15all STM32F429 variations (and even some STM32F4xx chips).
16
17This backend has no configuration options. The point of it is to provide bare-
18minimum platform code needed to do UART reads/writes.
19
20Setup
21=====
22This module requires relatively minimal setup:
23
24  1. Write code against the ``pw_sys_io`` facade.
25  2. Specify the ``dir_pw_sys_io_backend`` GN global variable to point to this
26     backend.
27  3. Build an executable with a main() function using a toolchain that
28     supports Cortex-M4.
29
30.. note::
31  This module provides early firmware init and a linker script, so it will
32  conflict with other modules that do any early device init or provide a linker
33  script.
34
35Module usage
36============
37After building an executable that utilizes this backend, flash the
38produced .elf binary to the development board. Then, using a serial
39communication terminal like minicom/screen (Linux/Mac) or TeraTerm (Windows),
40connect to the device at a baud rate of 115200 (8N1). If you're not using a
41STM32F429I-DISC1 development board, manually connect a USB-to-serial TTL adapter
42to pins ``PA9`` (MCU TX) and ``PA10`` (MCU RX), making sure to match logic
43levels (e.g. 3.3V versus 1.8V).
44
45Sample connection diagram
46-------------------------
47
48.. code-block:: text
49
50  --USB Serial--+    +-----STM32F429 MCU-----
51                |    |
52             TX o--->o PA10/USART1_RX
53                |    |
54             RX o<---o PA9/USART1_TX
55                |    |
56  --------------+    +-----------------------
57
58Dependencies
59============
60  * ``pw_sys_io`` facade
61  * ``pw_preprocessor`` module
62