How to calibrate radio via USB without main LiPo?

3DR Support,

Thank you very much for answering my last two questions. Here is one more for you. How do I calibrate my Pixhawk & DX9 without the main LiPo connected? My LiPo powers my Spektrum DS-X satellite Rx. If I remember correctly from my APM 2.5+ the LiPo and USB CANNOT be connected at the same time or there is a high potential to cook the board.


Thank you,


Hi Mike,

Two things:

1.Normally you can power both the Pixhawk and your receiver from the USB bus and calibrate the radio just fine that way.

There are exceptions and if you use one of the 3DR PPM encoders and a conventional receiver the USB is unlikely to provide sufficient power so you would also have to hook up the battery while calibrating the radio.

If your USB power is marginal, a powered USB hub can sometimes provide the additional power necessary

  1. But, in any case it is perfectly OK to hook up the battery at the same time the USB is hooked up. :open_mouth:

Obviously you do need to be very careful of propellers or remove them, but it will work fine.

The Pixhawk (and PX4 and APM for that matter) are specifically designed to allow this.

Best Regards,



Thank you for the clarification and guidance.

When I power up the DX9, the DS-X lights up but no changes are indicated on the calibration page. My guess is that I may need to re-bind and give it another go.


Update: I physically checked all connections to the pixhawk and did a re-bind between the Tx and the satellite Rx. Cannot calibrate radio. No stick or switch movement being displayed in APM Planner 2.0. Can’t arm motors, etc.

I also tried to access the CLI and the screen was displaying jibberish, not executing commands. Direct USB cable to my Apple MBP using APM Planner 2.0 via USB terminal connection at 115200.

Any ideas? Could my pixhawk firmware be corrupt?

This thread has been moved viewtopic.php?f=21&t=5828

Spektrum DX9 is NOT currently supported.