Dual serial communication

Hello all,

I have an Ardupilot 2.5 and I’m trying to communicate on both the 3DR radio (ground station with APM2) and USB serial (RPi to integrate with onboard systems) simultaneously.

If I connect only USB to RPi or Windows, I get comms. If I power USB port with battery and connect only radio, I get comms. If I connect both, I only get comms over USB and nothing over radio (green radio light, no red flashing). I have used raw terminal programs in both cases and see no data flow on the radio.

Does anyone know why I do not get any comms over radio when using USB comms?

The UART0 port is switched between the telemetry radio and the USB connection. To change the behaviour you need to change the solder pads on the bottom of the board.


Thanks for the quick response. I have come across a variation of this page before that gave me the idea that the solder jumpers force selects one UART or another, but now I understand that the default setup auto selects a UART and changing the solder jumpers will force USB onto UART 0 and radio onto UART 2, allowing simultaneous comms. Is this correct? Is there a reason why the default is automux, since this seems more restrictive?