Right Front Corner Servo Does Not Respond to Angles Below ~-21°

[Monke-Array]

Iam encountering an issue with the right front corner servo on our Open Source Rover (Rev F):
the servo connected to that corner does not respond to target angles below approximately -21°,
regardless of which physical servo is connected. The left corner servo (and others) work as expected.

Observed Behavior:
-The servo accepts and responds to angles above -21° normally.
-When commanded to angles below -21°, the servo does not move at all.
-Swapping in a known working servo (e.g., the left front) results in the same behavior on the right corner bus.

Steps Taken So Far:
-Swapped multiple servos to rule out hardware failure.
-Verified correct servo bus connections and power delivery.
-Confirmed ROS 2 /servo_wrapper node is publishing the same angle commands to left and right corners.
-Operating system is Ubuntu, running ROS 2 Iron.
-No PWM signal measurements yet, but open to doing so if helpful.

Hardware Setup:
-Rover revision: Rev F
-OS: Ubuntu (on Raspberry Pi)
-Servo node: /servo_wrapper
-ROS 2 Distro: Iron
-Motor controller: Roboclaw
-INA260 installed and active on bus 0x40

Suspicions:
-GPIO pin or PWM signal for the right corner servo might be clipped, saturated, or misconfigured in software.
-The Busses of INA260 and a Servo-Controller are overlapping.
-There could be a bug in the servo mapping or an electrical issue with signal range on that channel.

Request:

I’d appreciate help confirming:
-Whether this could be a known PWM mapping or electrical issue on Rev F.
-What the recommended debug steps are for servo PWM output validation.
-if there’s any calibration or limit configuration i may have missed.

[Achllle]

Hello and welcome! Happy to try to help here but just an FYI that you'll likely get most input from the community on the Slack group - see the main README page for instructions for joining. I remember some folks commenting on there that they had issues turning servo motors beyond 180 degrees, which sounds slightly different but perhaps is the same issue. link to Slack discussion

I'm not sure where you got 'Rev F' from, that is the denomination we used for the legacy rover, which didn't use servo motors. The releases are here and the control board is likely either v2.0.1 or v2.0.3.

Did you follow the instructions to calibrate the corner servos? If not done correctly, you will run into the limit of the servo motor.

I would recommend using the same script without any ROS 2 code to see if you can isolate the issue to a particular piece of software.
Hope that helps.

[Monke-Array]

Hello, thank you for your answer! I did the calibration correctly if you meant the one to set the servos to 150 and adjust them accordingly while they rotate freely and then edit the values for slight offsets.

I got the problem that i want to implement the inplace rotation correctly, but when i use the normal functions only two servos (left front and right back) make a 90° turn and then all wheels drive instead of each servo doing a 45° turn for rotation.

I tried to hardcode them with math.rad(45°) and -45° and so on but the turn was still to big. math.rad(22.5°) was as close as i could get to a 45° angle. But as i already described, the front right somehow wont accept -22.5° as an angle and i dont know why. I updated the software to the latest version of this repo and read the intructions carefully butt i still couldnt find the error. i will also write this question into the slack forum.

Thank you for your help!

[Achllle]

This code has worked for many people so I doubt the issue is with the higher level code - though debugging by simplification is a great way to isolate the issue.

In that slack thread I linked, @igillespie specified which version of ServoKit they're using:

pip3 show adafruit-circuitpython-servokit
Name: adafruit-circuitpython-servokit
Version: 1.3.18
Summary: CircuitPython helper library for PWM/Servo FeatherWing, Shield, and Pi HAT and Bonnet kits.
Home-page: https://github.com/adafruit/Adafruit_CircuitPython_ServoKit
Author: 
Author-email: Adafruit Industries <circuitpython@adafruit.com>
License: MIT
Location: /home/pi/myenv/lib/python3.11/site-packages
Requires: Adafruit-Blinka, adafruit-circuitpython-busdevice, adafruit-circuitpython-motor, adafruit-circuitpython-pca9685, adafruit-circuitpython-register
Required-by: mast_control, pca9685-kit

Can you run the same command to list yours, if different?

[Monke-Array]

Yes of course, here is the output:
Name: adafruit-circuitpython-servokit
Version: 1.3.18
Summary: CircuitPython helper library for PWM/Servo FeatherWing, Shield, and Pi HAT and Bonnet kits.
Home-page: https://github.com/adafruit/Adafruit_CircuitPython_ServoKit
Author:
Author-email: Adafruit Industries circuitpython@adafruit.com
License: MIT
Location: /home/rover/.local/lib/python3.10/site-packages
Requires: Adafruit-Blinka, adafruit-circuitpython-busdevice, adafruit-circuitpython-motor, adafruit-circuitpython-pca9685, adafruit-circuitpython-register
Required-by:

Is it normal that "required by" is empty?

[Monke-Array]

Hi, it was the ina which disrupted the nodes flow. One soldered bridge solved my issue. Thanks for your help!

[Achllle]

glad you figured it out!