There is only one other post on the forum that I could find about the RealPit VTX Power Switch. I have used these in the past with Betaflight builds and it is beneficial being able to remotely cut power to the VTX using a switch on my radio, whether it’s on the bench or in the field. The RealPit page does not provide instructions for ArduPilot, so I figured I would share how I did this in case it helps someone in future.
Here is a screen shot from Joshua Bardwell’s YouTube video on wiring this up.
My flight controller has unused M5, M6, M7, and M8 motor pads. So instead of soldering the signal wire to the LED pad like Bardwell, I soldered my signal wire to the M8 pad. I could have chosen any of the others, but M8 was the most convenient.
Then I read the documentation here: GPIOs
According to the GPIO page:
Usually, the first GPIO capable output is assigned pin 50, the second 51, etc.
In Mission Planner I changed:
SERVO8_FUNCTION = -1 (GPIO)
In my case, SERVO8 would be 57.
So I set RELAY1_PIN = 57
And then set RC8_OPTION = 28 (Relay1 On/Off). RC8 has no correlation to SERVO8, it’s just the channel I wanted to use on my radio.
Now, when I power up my vehicle, I can switch power on and off to the VTX with the push of a button on my radio. I have used this for analog and digital VTX and it works all the same.
Hopefully that helps someone in the future!