STM32H562: adding support for UART11/UART12

[daleka]

Hi everyone,

I'm working with a board based on STM32H562 (STM32H562VGT6, 12 hardware UARTs) and the STM32 port of MicroPython.

As far as I can see, the current STM32 port of MicroPython only has 10 UARTs described. But my board actually has 12 hardware UARTs, and I need to use UART11 (and later possibly UART12 as well). I tried to add UART11 support myself: the firmware builds and runs, but at baud rates higher than 9600 I start losing bits / getting corrupted data on UART11. At 9600 baud everything looks stable.

So I suspect that my changes are incomplete or incorrect somewhere (clocks, IRQs, array sizes, instance mapping, etc.).

What I changed

Base setup:

MicroPython: v1.26.1 (stm32 port, master at the time of work)

Board: custom, starting from boards/WEACT_H562RG as a reference.

1. mpconfigboard.h

In boards/WEACT_H562RG/mpconfigboard.h I added:

#define MICROPY_HW_UART11_TX (pin_A6) – DDCMP/DEX interface

#define MICROPY_HW_UART11_RX (pin_A7) – DDCMP/DEX interface

And set:

#define MICROPY_HW_MAX_UART (12)

This macro is now defined only in one place to avoid the previous “redefined” warning/error.

2. pins.csv

I added the corresponding AF entries for PA6/PA7 (UART11_TX / UART11_RX) in pins.csv, so that I can create machine.UART(11, ...) from MicroPython.

3. uart.c / uart.h

In uart.c and uart.h (STM32 port) I found the places where only 10 UARTs were listed and extended them to 11:

added the instance/handle description for UART11;

updated arrays/tables that list UARTs (handles, base addresses, numbers, etc.) to include UART11;

made sure the indexing matches UART number 11 and is not limited by the previous maximum of 10.

4. stm32_it.c

In stm32_it.c I added an interrupt handler for UART11, similar to the other UARTs:

defined the IRQ handler for UART11;

called the corresponding HAL/MicroPython function inside this IRQ.

After these changes the firmware successfully builds, flashes.

The problem

At 9600 baud data looks correct, I don't see obvious errors or losses.

At 19200 baud and higher I see lost bits / corrupted bytes.

It looks like either UART11 is not fully configured correctly at the low level, or the STM32 port of MicroPython is not fully prepared for UART indices > 10 (array sizes, IRQ tables, constants, buffers, or some other hidden limit).

The hardware itself should be OK: short cable, clean signal, other UARTs on the same board work at 19200 just fine.

What I'm looking for

Before I dig too deeply into the STM32 port internals, I wanted to ask the community:

Has anyone already used UART11 or UART12 on any STM32 board with MicroPython (H5/H7 or similar)?
If yes, I would really appreciate if you could share:

snippets from mpconfigboard.h with MICROPY_HW_UARTxx_*;

changes in uart.c / uart.h / stm32_it.c (or any other files where UART instances, tables, and IRQs are described);

pins.csv entries for these UARTs.

Is there any known limitation that MICROPY_HW_MAX_UART should not exceed 10 in the current STM32 port?
Or should it work fine with 12, as long as all tables/arrays and IRQs are correctly updated?

If someone already has a working board definition where UART11/12 run at higher baud rates (19200+ baud) without data loss, I'd be very grateful for example files or a small patch. That would make it much easier to compare with my changes and see where the mistake is.

Thanks in advance for any hints or example configs. If needed, I can upload the full mpconfigboard.h / pins.csv / diffs of my changes.