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Add busio support for ADI MAX32xxx port #10413

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@Brandon-Hurst Brandon-Hurst commented Jun 10, 2025

Add BUSIO Support for supported MAX32xxx devices. Not all capable MAX32 devices are supported yet; more support for MAX32650/MAX32666/MAX78002 boards may be added in a future PR. This module was tested on a MAX32690 board, the AD-APARD32690-SL. I used a ADT7140 I2C and MAX31723 SPI temperature sensor, and also tested the UART via the debug port serial connection.

  • BUSIO support added for MAX32 devices
  • Peripherals enumerated in peripherals/max32690 for MAX32690 MCU, including helper functions for mapping a set of pins to the associated on-chip peripheral
  • common-hal/busio contains the implementation of the BUSIO port functions

MAX31723 (SPI):
image

ADT7420 (I2C):
image

A simple echo test was done with UART as well with no issues:

from board import *
from busio import UART
 
# init uart with timeout of 10 seconds
uart = UART(P2_12, P2_11, baudrate=115200, timeout = 10.0)
 
# Write 'hello' to another serial port
uart.write('hello\n')
 
# Read 5 characters
uart.read(5)
 
# Read until newline
uart.readline()

Brandon-Hurst and others added 23 commits June 10, 2025 10:52
- Enabled BUSIO in mpconfigport.mk
- Stubs added for busio.I2C & busio.SPI
- Implemented busio.UART to basic working functionality
- Added MCU-specific UART data in peripherals/<mcu>/max32_uart.c & max32_uart.h
- Still have a couple issues where UART generates garbage characters or
  does not respond to timeouts / generate asynchronous IRQs
- Add debug-dap.sh to spawn OpenOCD process & gdb-multiarch process for debugging.
  Requires MaximSDK install & path settings inside this script.
  Also depends on gdb-multiarch and connected CMSIS-DAP probe over USB.
- debug-dap.gdb simply holds the gdb commands for this script

+ small style fix on common-hal/microcontroller/Pin.c
- Graceful recovery from timeouts added
- Remaining issue still exists where a timeout occurs after a while
- No ISR for UART writes, but uses timeouts
- Reads use ISRs, but also incorporate timeouts
- Formatting & codespell fixes from pre-commit
- Call NVIC_SetRAM in supervisor/port.c to move NVIC table to RAM, enabling ISR RAM remapping.
- Rename UART ISR to be generic for any UART IRQn.
- Remove background led writes from background.c.
- Data structure and constructor for I2C (tested)
- Lock and probing functions complete and tested

TODO: Implement I2C Write, Read, Wr/Rd

Signed-off-by: Brandon-Hurst <[email protected]>
Currently coupled a bit to APARD32690-SL board. Will refactor after testing BUSIO.SPI

Signed-off-by: Brandon-Hurst <[email protected]>
TODO:
- Figure out assigning CS Pins for SPI
- Test & Debug SPI / I2C

Signed-off-by: Brandon-Hurst <[email protected]>
Also reformatted pinmaps for SPI/I2C/UART on MAX32690

Signed-off-by: Brandon Hurst <[email protected]>
- Fixed errors with peripheral bus hardware descriptions in MAX32690 "peripherals/"
- Resolved all FIXME comments
- Removed unused ringbuf API from common-hal/busio/UART.c

Signed-off-by: Brandon Hurst <[email protected]>
- Add correct ringbuffer handling code to ports/analog/common-hal/UART.c

Signed-off-by: Brandon Hurst <[email protected]>
- Used direct hardware values to rely on common HW implementation
- Accounted for TX Lockout conditions in Transmit FIFO causing errors

Signed-off-by: Brandon Hurst <[email protected]>
- Probe function caused infinite loops / unreliable ACK values
- Replaced with probe-function with low-level routines

Signed-off-by: Brandon Hurst <[email protected]>
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@dhalbert dhalbert left a comment

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Thanks for continuing to flesh this out. The changes here are stylistic, to match how we do error messages, etc. elsewhere.

- Use existing error messages from locale/circuitpython.pot for
  most error messages
- Replace ConnectionError (networking specific) calls with others
  (usually RuntimeError)
- Remove '\n' from mp error calls (since they add it already)
- Remove some redundant validation code that repeats checks done
  by shared-bindings/common-hal/busio code. e.g. pin validation

Signed-off-by: Brandon-Hurst <[email protected]>
- Use m_malloc_without_collect storage API change from CircuitPython
- Remove err number for asynchronous read error; just report it

Signed-off-by: Brandon-Hurst <[email protected]>
- Remove excess argument from UART ringbuf malloc call
- Remove unused err and intfl0 in I2C driver to remove warnings

Signed-off-by: Brandon-Hurst <[email protected]>
@Brandon-Hurst Brandon-Hurst requested a review from dhalbert July 5, 2025 19:46
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Thanks for the comments, Dan! Helpful stuff. I have implemented the requested changes to the error reporting -- should be ready for another review now.

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