Telemetry - OpenLRS and APM


I have been trying to get telemetry to work with my OpenLRS RX and TX. Been trying out different setups and baud rates but not got it to work.


The transparent serial bridge is working perfectly but when I try to connect the RX to the APM Telemetry port (port 3) I cannot connect via Mission Control. Running a serial monitor I can see traffic - ascii in the beginning saying something like "<startup_mode: ground>" and then binary. Seems to be ok... but not good enough to connect.


I think the problem might be related to bandwidth. OpenLRS supports 750 byte/seconds from the RX to TX. After looking at the documentation and source code I have not figured out how much data MAVLink protocol is configured to send per second.

Does anybody know?



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    • I addition on the first-gen (100mw) OrangeRX openLRS from hobbyking the serial transport is non-functional. The code compiles, and the RC works, but serial is not functioning. When I downgrade to 3.5 it works. I tested it with a jumper connector the tx/rx pins on the RX, and serial FTDI on the TX.

  • Hi, I've made a custom firmware in order to make OpenLRS hardware work well with APM with a 1W bidirectional link.

    So far I've gone 10 km away with full APM telemetry. No need to modify anything on APM, no need to ctrl-T, all parameters are sent correctly, everything can be modified even during the flight, such as changing PID parameters or sending a new mission.Of course RC is sent as well.

    Described here :

    Discussed here :



  • I could really use some help here.

    I have the serial link working. I can enter the APM text menu with 3 enters on my hawkeye tx/rx combo serial link. I have the baud set to 9600 to try to make it work, using the stock OpenlrsNG, both flashed with most recent 3.5.6. So the data is going back and forth.

    As soon as I try to connect with my APM Planner, or Mission Planner, it will start to connect, waiting for data, then the led will go red on the RX, and i get nothing more, and lose servo control.

    Can anyone help me please, I am about to go nuts.

    • Try without connecting the DTR line from the serialport Göinge to the TX
      • Thanks for the input Martin.  I tried it, with pretty much the same issues.  I have made a video, hopefully i have missed something simple:

        My Video

  • Hey Martin,

    I'm trying to load this tree on my DTF UHF Deluxe and it says sketch too big. Is this still implemented. If so, How?


  • this might be posted somewhere else too but its something to look at if you haven't yet

    OrangeRX / OpenLRS 433Mhz hack#2 : 1W TX in the plane : APM long ra...

    the threads not to long and provides everything you need to accomplish a working long range telemetry setup


    • I'm flying since 6 month with this setup and it works fine. The main advantage is that it's based on two 1W TX, which makes a 1W bidirectional link.

      Today I've flown 10 km away, with still 80% good packets.

      It works with real 19200 bauds telemetry, no problem during initial parameters transfer etc.

  • My setup consists of Futaba 9C with Deluxe TX and Hawkeye 6 channel RX. APM en-route. I also ordered the 900 radio's as well just in case I couldn't get this to work.

    So, after reading a ton of info, I'm not having any luck uploading to my Hawkeye Deluxe TX. Is it possible at all? What gitsly version are you using? link? I did however (i think) successfully uploaded to the RX. When I choose option 6 for the Deluxe TX and Board type Leonardo I get errors. If I change the board type to the pro or pro mini, the sketch will verify but then says sketch too big.

    Help please.


  • I am trying to get telemetry going with APM and openlrsng.  I have it all set to 9600, and i can send test data from the tx to the rx, but not from the rx to the tx.  Occasionally some garbage data does come threw rx to tx, but not always.  All settings are 9600 8 1 N.  Is there a setting im missing, or has someone run into this before?


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