Pixhawk 6x + Radiomaster Boxer +Radiomaster ERLS RP3 V2

Hi !!
I am a teacher and I am new to the field of drones. I am currently in a project with students.
The equipment we have:
pixhawk 6x + Radiomaster Boxer + ELRS RP3 V2.
I paired the radio with the ELRS RP3 receiver (The red light is fixed)
The receiver is plugged into the RC IN pins of the pixhawk controller.

Qground controller is installed and I connected to pixhawk…but the radio does not connect to pixhawk…
How to do ? Thank you for any help that would help me in advance

missing a wire… coz you need use a full uart.
Just check the following link

1 Like

Hi! Thank you for your answer. There is no uart port to plug in the elrs rp3 receiver. According to the pixhawk 6x documentation, you must connect to the SBU/PPM receiver port: RC IN …

Your receiver have 4 pads… R is RX- T is TX - 5v is Voltage - G is Ground.

The RCIN pin its a timer input, CRSF/ELRS and SRXL2 require a true UART connection, so you need also change few parameters about your serial but i need investigate if elrs it’s supported by PX4

Thank you Dave84 four your answer.
1 : [https://www.expresslrs.org/quick-start/receivers/wiring-up/](Receiver Wiring - ExpressLRS)

Connect your receiver to any free UART on your Flight controller. Check your Flight Controller Wiring Manual which UARTs you can use.

  • The GND or G pad should be connected to any Ground pad on the Flight Controller(FC)
  • The VCC or 5 pad should be connected to any 5v (or 4v5) pad on the Flight Controller(FC)
  • The TX or T pad should be connected to an RX pad of the same UART number where the RX or R wire is on the Flight Controller(FC)
  • The RX or R pad should be connected to a TX pad of the same UART number where the TX or T wire is on the Flight Controller(FC)

I use TELEM 3 on Pixhawk 6x/

I used:
PIN 1 : Red (+5V)
PIN 2: Black: TX7/5/2 (out)_ +3.3V
PIN 3: Black: ___RX7/5/2 (in) ____+3.3V
PIN 6: Black:____GND___________GND

In the configuration of the serial port select the RCIN protocol. So for example for serial port 4:

Note: The serial port baudrate is automatically set and controlled by the firmware when any serial RC protocol, such as CRSF, is detected.

In https://ardupilot.org/plane/docs/common-holybro-pixhawk6X.html#compass

After, I do this:

  • Set RSSI_TYPE=3
    And all will be ok

How about signal levels / voltages?
The signal pins of the flight controller’s UARTs are all rated at 3V3 but the ELRS receiver has a working voltage of 5V.
I’m afraid to fry the expensive flight controller.



The 5v pin on the receiver its considered as an input pin so you don’t need be worried about damage your fc coz the receiver will receive power from the serial connector located on your FC.
Many advanced FC have a power IC protected by reverse voltage and over current protection.
Don’t confuse the 5V PIN with tx/rx volgate coz it’s considered signal