Fixes for AM32 Passthrough

[andyp1per]

Fixes some issues seen on AM32 passthrough. Tested on AM32 and BLHeli32

[tridge]

@MichelleRos could you test this on Nessie? It should make the am32.ca configurator more reliable with ArduPilot

[tridge]

or have you tested @Huibean ?

[Huibean]

or have you tested @Huibean ?

I have tested it, still some issue with am32.ca, I am adding firmware flash test to my config python script to confirm
https://github.com/Huibean/am32_config

[Huibean]

2024.01.21 test update

• Flight Controller: Holybro Pixhawk4 mini
• Reference Flight Controller Firmware: Betaflight
• ESC: Vimdrones ESC Dev Board
• last commit

commit d6ce6761145ab78a9fb6c1166a7a1fa22fc48427 (HEAD -> pr-am32-passthrough, andyp1per/pr-am32-passthrough)
Author: Andy Piper <[email protected]>
Date:   Wed Jan 8 16:28:05 2025 +0000

    AP_HAL_ChibiOS: reset DMA after exiting soft serial
    
    only configure DMA on groups that are actually being used for soft serial

• am32.ca Test

1. MSP connect
2. Params Read
3. Params Write
4. Write default params(reported bug on am32.ca, both not working on Betaflight)
5. Firmware Flashing(failed on Pixhawk4 min, success on Betaflight)

• Script Unit Test:

using https://github.com/Huibean/am32_config

first run

1. enter MSP
2. enter MSP passthrough
3. write default eeprom to bootloader only dev board
4. flash firmware
5. verify firmware booting and memory

second run

1. enter MSP
2. enter MSP passthrough
3. read eeprom param
4. flash firmware
5. verify firmware booting and memory

Pixhawk4 mini

Betaflight

[tridge]

@Huibean with the fw upload failure with this PR, does it also fail with master?

[Huibean]

Master should have issue enter the MSP pass through mode

[andyp1per]

Master should have issue enter the MSP pass through mode

Yeah @tridge master is more broken. Its not clear to me that anything is broken now with this PR apart from the web configurator

[rmackay9]

Although not directly related the AP AM32 DroneCAN ESC page includes instructions on how to update the firmware and set parameters using MP's DroneCAN page https://ardupilot.org/copter/docs/common-am32-escs.html

[andyp1per]

I think this should be considered for 4.6

[rmackay9]

This is included in AP-4.6.0-beta4