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These are the ramblings of Matthijs Kooijman, concerning the software he hacks on, hobbies he has and occasionally his personal life.

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Script to generate pinout listings for STM32 MCUs

Recently, I've been working with STM32 chips for a few different projects and customers. These chips are quite flexible in their pin assignments, usually most peripherals (i.e. an SPI or UART block) can be mapped onto two or often even more pins. This gives great flexibility (both during board design for single-purpose boards and later for a more general purpose board), but also makes it harder to decide and document the pinout of a design.

ST offers STM32CubeMX, a software tool that helps designing around an STM32 MCU, including deciding on pinouts, and generating relevant code for the system as well. It is probably a powerful tool, but it is a bit heavy to install and AFAICS does not really support general purpose boards (where you would choose between different supported pinouts at runtime or compiletime) well.

So in the past, I've used a trusted tool to support this process: A spreadsheet that lists all pins and all their supported functions, where you can easily annotate each pin with all the data you want and use colors and formatting to mark functions as needed to create some structure in the complexity.

However, generating such a pinout spreadsheet wasn't particularly easy. The tables from the datasheet cannot be easily copy-pasted (and the datasheet has the alternate and additional functions in two separate tables), and the STM32CubeMX software can only seem to export a pinout table with alternate functions, not additional functions. So we previously ended up using the CubeMX-generated table and then adding the additional functions manually, which is annoying and error-prone.

So I dug around in the CubeMX data files a bit, and found that it has an XML file for each STM32 chip that lists all pins with all their functions (both alternate and additional). So I wrote a quick Python script that parses such an XML file and generates a CSV script. The script just needs Python3 and has no additional dependencies.

To run this script, you will need the XML file for the MCU you are interested in from inside the CubeMX installation. Currently, these only seem to be distributed by ST as part of CubeMX. I did find one third-party github repo with the same data, but that wasn't updated in nearly two years). However, once you generate the pin listing and publish it (e.g. in a spreadsheet), others can of course work with it without needing CubeMX or this script anymore.

For example, you can run this script as follows:

\$ ./stm32pinout.py /usr/local/cubemx/db/mcu/STM32F103CBUx.xml
name,pin,type
VBAT,1,Power
PC13-TAMPER-RTC,2,I/O,GPIO,EXTI,EVENTOUT,RTC_OUT,RTC_TAMPER
PC14-OSC32_IN,3,I/O,GPIO,EXTI,EVENTOUT,RCC_OSC32_IN