matek H743-slim can't connect with mavros by usb

[UAVlover]

Describe the bug

I try to use mavros to connect matek H743-slim with my PC, but it failed. ttyACM0 can be found by computer, but there is no mavlink message.

To Reproduce

Steps to reproduce the behavior:

1. flash FC with bootloader and Firmware
   2.Connect FC to the PC by usb
2. roslauch mavros px4.launch

Expected behavior

H743-slim can connect with mavros by usb

Log Files and Screenshots

HW arch: MATEK_H743_SLIM
FW git-hash: dc7f29e
FW version: 1.13.1 0 (17629440)
OS: NuttX
OS version: Release 10.2.0 (167903487)
OS git-hash: 91bece51afbe7da9db12e3695cdbb4f4bba4bc83
Build datetime: Oct 14 2022 15:45:51
Build uri: localhost
Build variant: default
Toolchain: GNU GCC, 9.3.1 20200408 (release)
PX4GUID: 0006000000003337333931305113004a0031
MCU: STM32H7[4|5]xxx, rev. V
INFO [param] selected parameter default file /fs/microsd/params
INFO [param] importing from '/fs/microsd/params'
INFO [parameters] BSON document size 1411 bytes, decoded 1411 bytes (INT32:31, FLOAT:43)
INFO [param] selected parameter backup file /fs/microsd/parameters_backup.bson
Board architecture defaults: /etc/init.d/rc.board_arch_defaults
Board defaults: /etc/init.d/rc.board_defaults
INFO [dataman] data manager file '/fs/microsd/dataman' size is 62560 bytes
Loading airframe: /etc/init.d/airframes/4001_quad_x
INFO [uavcan] Node ID 1, bitrate 1000000
Board sensors: /etc/init.d/rc.board_sensors
icm42605 #0 on SPI bus 4 rotation 14
mpu6000 #0 on SPI bus 1 rotation 12
dps310 #0 on I2C bus 2 address 0x76
ERROR [SPI_I2C] qmc5883l: no instance started (no device on bus?)
ERROR [init] Failed loading mixer: /etc/mixers/quad_x.main.mix
INFO [init] setting PWM_AUX_OUT none
ekf2 [567:237]
Starting Main GPS on /dev/ttyS1
Starting MAVLink on /dev/ttyS2
INFO [mavlink] mode: Onboard, data rate: 50000 B/s on /dev/ttyS2 @ 500000B
Board extras: /etc/init.d/rc.board_extras
atxxxx #0 on SPI bus 2
Addons script: /fs/microsd/etc/extras.txt
WARN [mavlink] mavlink for device /dev/ttyACM0 is not running
INFO [logger] logger started (mode=all)

Add screenshots to help explain your problem.

Drone (please complete the following information):

• Matek H743-Slim V1.5

Additional context

from the log, I found FC didn't start mavlink at ttyACM0. However, I have found that if I connected with QGC firstly, then closed QGC, after these operations, FC can be connected with mavros. I did some tests as follows, which proved my idea. Becuase of my poor experience, I have failed to fix this bug.

*connected with minicom
nsh> mavlink status

instance #0:
mavlink chan: #0
type: GENERIC LINK OR RADIO
flow control: OFF
rates:
tx: 14016.1 B/s
txerr: 0.0 B/s
tx rate mult: 1.000
tx rate max: 50000 B/s
rx: 0.0 B/s
rx loss: 0.0%
FTP enabled: YES, TX enabled: YES
mode: Onboard
MAVLink version: 1
transport protocol: serial (/dev/ttyS2 @500000)
nsh>

• connected with QGC mavlink console
  nsh> mavlink status

instance #0:
mavlink chan: #0
type: GENERIC LINK OR RADIO
flow control: OFF
rates:
tx: 15446.7 B/s
txerr: 0.0 B/s
tx rate mult: 1.000
tx rate max: 50000 B/s
rx: 0.0 B/s
rx loss: 0.0%
FTP enabled: YES, TX enabled: YES
mode: Onboard
MAVLink version: 1
transport protocol: serial (/dev/ttyS2 @500000)

instance #1:
GCS heartbeat valid
mavlink chan: #1
type: USB CDC
flow control: ON
rates:
tx: 18914.9 B/s
txerr: 0.0 B/s
tx rate mult: 1.000
tx rate max: 100000 B/s
rx: 47.0 B/s
rx loss: 0.0%
Received Messages:
sysid:255, compid:190, Total: 56 (lost: 0)
FTP enabled: YES, TX enabled: YES
mode: Config
MAVLink version: 2
transport protocol: serial (/dev/ttyACM0 @2000000)
ping statistics:
last: 0.60 ms
mean: 0.53 ms
max: 46.70 ms
min: 0.25 ms
dropped packets: 0

• script didn't work
  Addons script: /fs/microsd/etc/extras.txt
  INFO [mavlink] mode: Config, data rate: 100000 B/s on /dev/ttyACM0 @ 2000000B
  ERROR [mavlink] could not open /dev/ttyACM0
  INFO [logger] logger started (mode=all)

NuttShell (NSH) NuttX-10.2.0

[UAVlover]

I added " mavlink start -d /dev/ttyACM0 " at the last line of rcS, and create /etc/extras.txt in SD card with "mavlink start -d /dev/ttyACM0" , it worked well now.