Ultimate LRS and Pixhawk

Introduction

If you’ve got a pixhawk or compatible flight controller, you may be interested in using it with Ultimate LRS for a high performance, full telemetry and 16 channels long range system.

Pixhawk specific serial port configuration

In Mission Planner, you’ll configure the serial port to use for telemetry.

Example : If you choose ‘TELEM1‘, in Mission Planner change the parameter ‘SERIAL1‘ to 19, meaning 19200 bauds.

Remark : this is different from APM users who will be choosing ‘SERIAL1’ for UART0

Connections

RC Control

  • PPM out on ULRS Rx to RC Signal input on Pixhawk
  • GND out on ULRS Rx to RCin GND on Pixhawk

Telemetry

  • Tx on ULRS Receiver to Rx in on TELEM1
  • Rx on ULRS Receiver to Tx in on TELEM1
  • GND on ULRS Rx to GND in on TELEM1

Power

  • ULRS Receiver powered directly from battery (preferred) or 5V regulator
  • Don’t power ULRS from the Pixhawk RCin Vcc
  • Complete information about powering Pixhawk can be found here.

Pixhawk pinout

Pixhawk Power connector pinout

More details here.

Pixhawk telemetry connector pinout

More details here.

Remark : Pixhawk uses 3.3V signal on its telemetry port.

Resources

 

12 comments

  1. Pawel says:

    Hi,

    I am impressed by your work, and I am about to buy two Orange units, and use them with Pixhawk. However, I have two questions.

    I want to use Orange TX 1W module as a receiver. You say that it can be powered from 5V BEC, or from battery up to 30V. But on Hobbyking page I can see: Voltage input: 6.8~12VDC. Is Hobbyking wrong?

    The second doubt is about PPM signal compatibility. I heard about problems with PPM pulse length with some OpenLRS software. Does Ultimate LRS produce PPM signal which is understandable by Pixhawk?

    Pawel

    • admin says:

      Hi Pawel,

      Regarding the power supply, the regulator of the 1W units is a tsr1-2433. According to its datasheet this module can support up to 36V input under 1A, and the ULRS is using far less than 1A, so no problem to power from 36V. And it’s a switching regulator, it won’t heat.

      For the PPM, there’s no issue (there was an issue years ago when APM didn’t support 3ms end of frame pulse, but now it does since years), you can use it with common flight controllers including APM and Pixhawk.

      There was an issue with the Pixracer, but it appeared to be a bug in APM, which was looking for an inverted PPM signal and this bug was corrected by the APM team a few days ago.

  2. Greg says:

    Hi,

    The new PX4 ix using telemetry at 57600 speed and this cannot be currently changed. Is there a way to reconfigure UltimateLRS so it works with telemetry @ 57600?

  3. NEVdD says:

    Hello, is the serial transmission somehow specific to APM telemetry or is it possible to transmit any kind of data?
    Thank you again for your awesome work!

  4. EpsiOne says:

    Could it work with the new smaller versions of the Pixhawk?
    • AUAV-X2 autopilot –
    • PixFalcon Micro –

    • admin says:

      The ULRS acts as a simple (wireless) serial cable, it’s transparent to whatever goes through it, so it should work with these Pixhawk versions too.

  5. Riccardo Spagni says:

    Am I correct in saying that this will transmit all the channels from my controller to the unit acting as a receiver, and the Pixhawk will see all 16 channels as if I had a 16 channel receiver + a PPM connection?

    I’m trying to replace my EzUHF Diversity receiver with this (and also then be able to remove my jDrones long range telemetry radios), but since I use all 12 channels on the EzUHF I’d have to switch to using the aux out ports on the Pixhawk, and setting up pass-throughs for them.

    • admin says:

      The current version is limited to 8 channels, you’ll have to wait a few days for the next version. It will support 16 channels, and will provide several ways to access the channels 9-16.

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