UAVCAN Disables servo PWM output

PX4 Autopilot Drivers
#1

Dear all,

When I enable the UAVCAN for VTOL ESCs, the PX4 stops outputting PWM to servos. I verified this with an oscilloscope. However, it can still output PWM temporarily, if motor test commands from the Qgroundcontrol is sent.

When the UAVCAN_ENABLE = 3, SERVO_OUTPUT_RAW message at the MAVLink inspector is like below. Obviously it is sending all surface values from the UAVCAN. However I need surface 1, 2, 3, 4 as PWM while 5,6,7,8 are UAVCAN.

May someone guide me on this issue about which part of the source code I need to do such modification?

  • In Fixed Wing Mode

1
1964×315 254 KB

  • In Multirotor Mode

2
2965×317 255 KB

  • When UAVCAN_ENABLE = 0 (The values are PWM microseconds)

3
3964×316 255 KB

Surface mapping is:

  • Servo_1: Aileron
  • Servo_2: Left Ruddervator
  • Servo_3: Forward propulsion ESC
  • Servo_4: Right Ruddervator
  • Servo_5: Front Right VTOL ESC
  • Servo_6: Rear Left VTOL ESC
  • Servo_7: Front Left VTOL ESC
  • Servo_8: Rear Right VTOL ESC
#2

Yes this is how it works. We also fought it. In the end, I solved it by having ESC controlled via RCPWM output and telemetry data via UAVCAN.

You can find more posts discussing this issue.

It would be ideal to have a separate mixer for UAVCAN and a separate mixer for PWM.

#3

i have been searching how to set up uavcan servos in PX4 for awhile. in your setup, have you check the output pins whether they generate signals?