Arduboat pixhawk with Relay setup

Dear All,

I would like to connect 2 relay switch module to pixhawk rover firmware 3.1.1 and I would like to use FS-i6S transmitter SWA and SWB to control a relay to on off LED light,

How can I do for this function?

in a below picture it’s my first Arduboat setup.



Phuket Thailand

Assign your two switches to two spare channels, then set the RC pass through two free outputs on the pixhawk :slight_smile:

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Please can you tell me how to connect the servos with the pixhawk and how to setup my transmitter in mission planner??
Many regards

Thank you so much I will try it

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Hi - Mookai and all - has anyone had success getting multiple relays to work on latest Pixhawk with latest Rover/Boat ?

  • The system is armed, I have multiple servos working fine.
  • I have 2 Taranis switches configured to control relays on RC CH 5 & 6.
  • On Mission Planner/Servo Output page I have CH 5 & 6 configured as “RC Passthru” and the outputs appear to respond correctly when I flip the switches
  • RELAY_PIN = 54, RELAY_PIN2 = 55 which should set pixhawk AUXOUT 5 & 6 to relay pins
  • SERVO13_FUNCTION = 55, SERVO14_FUNCTION = 56, which (I think) should map RC Channels 5 & 6 to Pixhawk AUXOUT 5 & 6
  • Despite configuration above, I can get no voltage out of AUXOUT 5 or 6.

What am I missing ??


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sound like you have it mostly right,

current your mapping aux out 5 and 6 to be both relay and servo output. To get just the relay output you will need to set SERVO13_FUNCTION and SERVO14_FUNCTION to 0 for disabled.

Then to allow the aux pins to do something other than pwm out you need to reduce the brd_pwm_count parameter to 4. ie out of a possible 6 4 will be pwm and the last 2 are now free to do relays.

In order to control the realys you need to set the rcx_option, for 5 and 6 it would be rc_5option and rc_6option to functions 34, 35 or 36 for relay 2,3, or 4. See :

it looks like there is no option for relay one, i guess its reserved for motor direction changing with dc motors, so you may have to adjust your settings to use relay 2 and 3.

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Thank you Peter,

According to, the parameters used to control the output channels has changed from RCx_FUNCTION to SERVOx_FUNCTION in current firmware versions. Using latest Mission Planner connected to latest rover, there is no RCx_FUNCTION, only SERVOx_FUNCTION, and per there is no way to set a relay function there.

So… do I need to go back to older firmware ? Seems unlikely developers would have removed or broken such commonly used functionality tho.

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RCx_OPTION is for inputs to the flight controller from the rc receiver.

SERVOx_FUNCTION is for outputs from the flight controller via the servo ports.

You may have to flash a beta or latest (master) release to get RCx_OPTION, if its not in the stable then it is still the old ch7_function and ch8_function. The old parameters should have the same options, there just available on fewer input channels.

Yeah there is not servo output function to a relay because a relay does not take a servo type pwm output, relays are setup using the RELAY_PIN parameters. You will have to disable pwm and reduce the brd_pwm_count for the aux pins in order to disable there servo outputs and allow the relay functions to use the pin instead.

Dear all,


I have connected a relay switch module to pixhawk (rover firmware 4.0.0) and I can change it with dedicated buttons of the Joystick, but I would like to switch it with the same buttons I use to arm and disarm the system.

Could you help me configure the parameters to do that?


Hi mookai1973,

I have a RoboClaw 2x60A Motor Controller wiring to a Pixhaw to control two trolling motors.
I only have got to work ok with analog signal setup on BasicMicro Motion Studio and also I need to deselect the mixing option. I thought it must be setup as RC signal but it doesn’t work at all.
On the other hand, I have a couple of extrange things…I must to set the MOT_SAFE_DISARM = 0 (0:PWM enabled while disarmed 1:PWM disabled while disarmed) because if I set to “1” the motors run at high speed when disarm the system…
The motors Works ok (tank style) but I need to select PILOT_STEER_TYPE = 0 (0:Default 1:Two Paddles Input 2:Direction reversed when backing up 3:Direction unchanged when backing up) instead of “1” as seems the correct option.
Further, when I switch off and on it seems like the Roboclaw loss the saved setup or something like that because I need to connect (usb connection to PC) and select/deselect the mixing parameter and it Works fine again…I don’t understant what happend…
I have Rover 4.0.0 and the motors are wiring to servo1 and 3 with 73 and 74 servox_function
The idea is to control a boat in Skid Steering mode. the motors are used to turn the boat, aditionally I have a big motor managed by a 3 phases speed frecuency regulator connect to servo2 output setup as 70 (Throttlle) by a PWM converter and it Works fine when I control the system with the Logiteck joystic. No test in auto mode yet.

The main question here is Why Roboclaw doens’t work if I select RC control, that means the motor doesn’t move at all. If I select Analog control, I can control them via telemetry by Pixhawk otuput as I explained above, but it seems the logic option must be “RC control” because the Pixhawk can’t take out analog signal…so I am afraid the “extrange” problems I have are due to selecting “Analog Control”, even if the motors seem to work…

Any ideas??
params_08062020.param (16.8 KB)