Problems with pwm outputs and other issues


I have a BlueROV equipped with the heavy configuration kit. Additionally I installed two Blue Trail Engineering SER-2020 servo motors (

I am using the Navigator Flight Controller + Raspberry Pi 4 setup. The ardupilot version is 4.1.2, and the correct frame configuration has been selected (vectored 6DOF). To sum up I have 12 devices connected to the Navigator Flight Controller PWM channel outputs:

Device (s) PWM output channel
Thruster’s ESCs 1-8
Lumen light* 12
SER-2020 13 and 15
Camera tilt servo 16
N/C 9-11, 14

*it is just one Lumen light not two.

I have the following issues and I do not know if there is a relationship between them:

1.- Sometimes after I turn the BlueROV on, QgroundControl shows a pre-arm check failure (imu_reset or sth like that), an intermitent error with the AHRS and the voltage readings on the interface oscillate between 3.71 V and the actual battery voltage (~15V). When this happens I cannot operate the ROV, but if I restart it, sometimes it works, the errors dissapear and I can arm/disarm and operate the ROV and the thrusters normally. However, in both cases I cannot operate the other (12-16) PWM outputs, even though the joystick is mapped properly and the readings show that the PWM values change when I press the corresponding buttons.

2.- While working in the BlueOS interface sometimes I lose the heartbeat due to multiple errors like these:


I get like 15+ notifications with different errors, this happens sometimes with the Autopilot and sometimes with the SITL

3.- I decided to use the SITL instead and try to operate the PWM outputs using the Navigator Assistant extension but as soon as I press the “toggle PWM enable” button the ROV goes haywire; the lumen light turns on, the ESCs start beeping (and do not stop), the servos move to a position (the one set by the sliders I think). When I disable the PWM everything stops.

This last case also happened when using the Autopilot, however I thought it was a compatibility issue with the Navigator Assistant, that is why I changed to the SITL but it did not solve the problem.

To summarize: I cannot operate the PWM outputs with the joystick (while using QGroundControl), nor the navigator assistant (because everything goes haywire when I enable the PWM outputs).

I checked the connections and it does not seem to be any shortcircuit or faulty wiring, and if that can be a possibility, where should I look first?

I do not where to start troubleshooting

Any help or suggestion is welcomed

Have a good day! :smiley:

Hi @Alex_UJI1 -
Happy to help. In answer to your questions -

  1. It sounds like you may have a bad connection from the power sensor and the Navigator, or a failing analog to digital converter.
    As for your PWM outputs for the servo, can you share how you’ve configured your joystick mapping? Ardusub technically only supports three channels (Servo 1,2,3) on Aux 1,2,3, this corresponds to Navigator ports 9, 10 and 11.
  2. While annoying, those BlueOS warning messages are likely not an issue. They may be occurring because your vehicle lost connection to the local WiFi network?
  3. The Navigator WebAssistant completely disables the autopilot connection to PWM outputs and sensors, that is why everything seems to go “haywire” when activated. It is not possible to use this extension in parallel with ArduSub/ArduRover.

Hello Tony,

  1. How can I check if the analog to digital converter is failing?
    This is how the servos and the joystick are configured:



Since I am using the servos to mimic a pan-tilt behavior I thought I could use those settings. In this case I am not interesting in moving the camera tilt system, in fact the output where the camera servo is connected is disabled. I also checked and the SER-2020 can operate in a range of 800-2200μs. I know that the function is capped at a range of 1100-1900 but in this case it does not matter.

2.- Yes in this case was the WiFi (maybe I chose a bad example there), but sometimes is the heartbeat or other important stuff. And when powered on it works well in most cases but after some minutes the heartbeat is lost and all these notifcations start to appear: wifi, system information, autopilot manager, etc

3.- OK, so what would I need to do in order to prevent the system going “haywire” and operate the Navigator WebAssistant correctly