[Bug] matek_h743-slim v3 UART6 is mapped to /dev/ttyS5 instead of /dev/ttyS4

[dronetastic]

Describe the bug

I have connected my CrossFire receiver to rx6/tx6 on the board. I configured the crossfire option in the firmware, compiled and installed it, but in QGroundControl, selecting UART6 picks /dev/ttyS5. The radio does not work, but if I manually select /dev/ttyS4 in the mavlink console, it does.

src/board_config.h contains:
#define RC_SERIAL_PORT "/dev/ttyS4"

This is correct, except it's not labelled as such on the flight controller, and for CRSF, there is no option to pick the RC serial port anyway.

To Reproduce

enable CRSF in the firmware
compile and upload matek-h743-slim-default
Connect the CRSF receiver to RX6/TX6 on the board

nsh> crsf_rc status
INFO  [crsf_rc] UART device: /dev/ttyS5
INFO  [crsf_rc] UART RX bytes: 0
INFO  [crsf_rc] Telemetry: yes
crsf_rc: cycle interval: 138 events, 103938.66us avg, min 103051us max 106404us 650.002us rms
crsf_rc: publish interval: 137 events, 103933.49us avg, min 103116us max 106404us 558.808us rms
Disposed bytes: 0
Valid known packet CRCs: 0
Valid unknown packet CRCs: 0
Invalid CRCs: 0
Invalid known packet sizes: 0
Invalid unknown packet sizes: 0

Run:

nsh> crsf_rc stop
nsh> crsf_rc start /dev/ttyS4

nsh> crsf_rc status
INFO  [crsf_rc] UART device: /dev/ttyS4
INFO  [crsf_rc] UART RX bytes: 103050
INFO  [crsf_rc] Telemetry: yes
crsf_rc: cycle interval: 7826 events, 9636.24us avg, min 4038us max 20224us 5860.551us rms
crsf_rc: publish interval: 7827 events, 9636.11us avg, min 4037us max 20110us 5861.506us rms
Disposed bytes: 0
Valid known packet CRCs: 4138
Valid unknown packet CRCs: 0
Invalid CRCs: 0
Invalid known packet sizes: 0
Invalid unknown packet sizes: 0

You can see it connects correctly.

Expected behavior

Since the ports on the board are labelled as uart 1-7, I think the options should reflect the same. I also think the RC_SERIAL_PORT should be available in the setup dropdown.

Screenshot / Media

No response

Flight Log

No response

Software Version

HW arch: MATEK_H743_SLIM
PX4 git-hash: 93eef0c
PX4 version: 1.15.1 0 (17760512)
PX4 git-branch: release/1.15
OS: NuttX
OS version: Release 11.0.0 (184549631)
OS git-hash: 5d74bc138955e6f010a38e0f87f34e9a9019aecc
Build datetime: Oct 23 2024 16:47:39
Build uri: localhost
Build variant: default
Toolchain: GNU GCC, 10.3.1 20210621 (release)
PX4GUID: 00060000000039313330323351050047003e
MCU: STM32H7[4|5]xxx, rev. V

Flight controller

No response

Vehicle type

None

How are the different components wired up (including port information)

crossfire nano pro wired to RX6/TX6

Additional context

No response