can't switch on RELAY0 after arming when motor type is set to BrushedWithRelay

[jazzl0ver]

Bug report

Issue details

After firmware upload, the parameters were reset to their defaults and then applied these and rebooted:

ARMING_CHECK,0
BRD_PWM_COUNT,2
BRD_SAFETYENABLE,0
MOT_PWM_TYPE,3
RELAY_PIN,52
RELAY_PIN2,53
RELAY_PIN3,54
RELAY_PIN4,55
SERVO11_FUNCTION,-1
SERVO12_FUNCTION,-1
SERVO13_FUNCTION,-1
SERVO14_FUNCTION,-1

The testing procedure:
A voltmeter is connected to the control pins of AUX3 and AUX4. Before arming, a voltage has been measured between the pins when RELAY0 is set to HIGH and RELAY1 is set to LOW and vice versa using Mission Planner's Servo/Relay tab. In both cases, the voltage raised to +-~3.3V.
After arming the same measurement has been conducted with the following results:
RELAY0:HIGH, RELAY1:LOW - voltage starting to grow but then quickly goes back to 0V (expected to be 3.3V)
RELAY0:LOW, RELAY1:HIGH - voltage is 3.3V (as expected)

Voltage between to the control pins of AUX5 and AUX6 is +-3.3V as expected regardless of the arming state.

Changing motor type from BrushedWithRelay to Normal (and rebooting) gets rid of this issue.

Version
4.3.0-dev
4.2.0-rc1
4.1.5-stable
3.5.2-stable

Platform
[X] Rover

Airframe type
N/A

Hardware type
Pixhack 2.8.4 (a Pixhawk clone)

Logs
N/A

[IamPete1]

Brushed with relay uses relay 0 through 4 depending on how many motors have setup. When configured for this this you cannot set the relays manually when the motors are active.

[jazzl0ver]

@IamPete1 thanks for quick reply! Is this behavior documented somewhere (I checked Brushed Motors and Relay wiki pages and found nothing regarding this)?

I was able to shift the relays and keep the pins 3-6 (AUX3-AUX6):

RELAY_PIN,50
RELAY_PIN2,51
...
RELAY_PIN6,55
SERVO9_FUNCTION,-1
...
SERVO14_FUNCTION,-1

And now AUX3 pin works as expected. Thanks!

In my setup I use two servo outputs: PWM1 is for steering, PWM2 is for throttle. Can you please explain why I had problems only with RELAY0?

[IamPete1]

RELAY0 is being used for direction by your throttle output.

[jazzl0ver]

No docs on that, right?

[IamPete1]

Not really, we do have:

https://ardupilot.org/rover/docs/common-brushed-motors.html#connection-and-configuration

If you fancy helping us improve them that would be great.

https://ardupilot.org/dev/docs/common-wiki_editing_guide.html

[jazzl0ver]

Finally completed a short guide on how to make things work:
https://github.com/jazzl0ver/ardupilot-rover-l298n

Thanks again for your help!