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stm32: Update pyb.CAN loopback unit tests for FDCAN, fix CAN2 filter bug#18946

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Mar 18, 2026
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stm32: Update pyb.CAN loopback unit tests for FDCAN, fix CAN2 filter bug#18946
projectgus merged 4 commits into
micropython:masterfrom
projectgus:bugfix/stm32_pyb_can_tests

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@projectgus projectgus commented Mar 18, 2026

Summary

  • Updates the loopback unit tests in tests/ports/stm32/can*.py to pass on CANFD hardware, renames them to pyb_can*.py to account for incoming machine.CAN functionality.
  • As part of updating pyb_can2.py to work with FDCAN, was also able to fix STM32 pyb.CAN: Instantiating one CAN instance can corrupts settings of another instance. #18922 and make that unit test a regression test for it.
  • Cleaned up some parameter names and types for can_clearfilter() as they weren't very clear.
  • Enabled CAN2 peripheral on the NUCLEO_G474RE board, as used for testing.

This work is to support #18572 - now tests pass for pyb.CAN we can verify there's no regression when adding machine.CAN. Have made into a separate PR as the other is already too big!

Testing

  • Ran ports/stm32/pyb_can*.py unit tests on PYBDV11 (Classic CAN), NUCLEO_G474RE and NUCLEO_H723ZG boards (both flavours of FDCAN). All now passing.
  • Connected a CAN transceiver to CAN2 on NUCLEO_G474RE and confirmed the CAN bus also works on the configured pins in non-loopback mode.
  • NUCLEO_H723ZG doesn't have externally usable FDCAN2 pins without changing solder jumper settings (and possibly other things), so I didn't commit the change to this PR as it's only immediately usable for loopback tests. For refernece, the patch for loopback testing is:
--- a/ports/stm32/boards/NUCLEO_H723ZG/mpconfigboard.h
+++ b/ports/stm32/boards/NUCLEO_H723ZG/mpconfigboard.h
@@ -97,6 +97,10 @@
 #define MICROPY_HW_CAN1_TX                  (pin_D1)
 #define MICROPY_HW_CAN1_RX                  (pin_D0)
 
+#define MICROPY_HW_CAN2_NAME                "FDCAN2"
+#define MICROPY_HW_CAN2_TX                  (pin_B13) // B13, B6
+#define MICROPY_HW_CAN2_RX                  (pin_B12) // B12, B5
+
 // SD card detect switch
 #define MICROPY_HW_SDCARD_DETECT_PIN        (pin_G2)
 #define MICROPY_HW_SDCARD_DETECT_PULL       (GPIO_PULLUP)

Generative AI

I did not use generative AI tools when creating this PR.

@projectgus projectgus requested a review from dpgeorge March 18, 2026 05:08
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codecov Bot commented Mar 18, 2026 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.45%. Comparing base (df9b714) to head (22ee568).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files 
@@           Coverage Diff           @@
##           master   #18946   +/-   ##
=======================================
  Coverage   98.45%   98.45%           
=======================================
  Files         175      175           
  Lines       22635    22635           
=======================================
  Hits        22286    22286           
  Misses        349      349

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@projectgus projectgus force-pushed the bugfix/stm32_pyb_can_tests branch from 28061d9 to 68aa819 Compare March 18, 2026 05:14
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github-actions Bot commented Mar 18, 2026 •
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Code size report:

Reference:  esp32: Only check the lockfile currently used by the build. [82c6b0e]
Comparison: stm32: Expose FDCAN2 on board NUCLEO_G474RE. [merge of 22ee568]
  mpy-cross:    +0 +0.000% 
   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:   +12 +0.003% PYBV10
      esp32:    +0 +0.000% ESP32_GENERIC
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32

dpgeorge
dpgeorge reviewed Mar 18, 2026
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Comment thread tests/ports/stm32/pyb_can_classic_rx.py Outdated
dpgeorge
dpgeorge reviewed Mar 18, 2026
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Comment thread ports/stm32/can.h Outdated
dpgeorge
dpgeorge reviewed Mar 18, 2026
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Comment thread tests/ports/stm32/can2.py
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dpgeorge commented Mar 18, 2026

Apart from the comments above, this looks really good, thanks! I tested on PYBV10 and PYBD_SF6, running the new tests both before and after the bug fix to the firmware in this PR. The expected part of the test fails prior to fixing the CAN2 filter issue, and they all pass with the fix (ie with firmware compiled from this PR).

@projectgus projectgus force-pushed the bugfix/stm32_pyb_can_tests branch from 68aa819 to 05744b0 Compare March 18, 2026 06:08
@projectgus
tests/ports/stm32/can: Update pyb.CAN tests for FDCAN.
c5a91b5 
Also rename the prefix from can to pyb_can, in anticipation
of machine.CAN tests.

Signed-off-by: Angus Gratton <[email protected]>
@projectgus
stm32/pyb_can: Fix initialising CAN2 clearing CAN1 filters.
3462973 
Closes micropython#18922

Signed-off-by: Angus Gratton <[email protected]>
@projectgus
stm32/can: Clarify can_clearfilter() arguments.
b5107f8 
The function arguments mean totally different things for Classic vs FDCAN
hardware, but the argument name wasn't particularly clear for either.

This commit shouldn't really change the binary firmware at all.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <[email protected]>
@projectgus
stm32: Expose FDCAN2 on board NUCLEO_G474RE.
22ee568 
This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <[email protected]>
@projectgus projectgus force-pushed the bugfix/stm32_pyb_can_tests branch from 05744b0 to 22ee568 Compare March 18, 2026 06:15
dpgeorge
dpgeorge approved these changes Mar 18, 2026
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Retested on PYBD_SF2 and PYBD_SF6 and the updated tests work.

@projectgus projectgus merged commit d1c936d into micropython:master Mar 18, 2026
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@projectgus projectgus deleted the bugfix/stm32_pyb_can_tests branch March 18, 2026 22:37
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projectgus commented Mar 18, 2026

Thanks for the quick review, @dpgeorge! Have merged so I can more easily rebase the machine.CAN PR.

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dpgeorge commented Mar 18, 2026

Excellent!

@projectgus projectgus mentioned this pull request Mar 19, 2026
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STM32 pyb.CAN: Instantiating one CAN instance can corrupts settings of another instance.

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