er9x TX with Ardupilot interface

Well the er9x TX and ardupilot combo is finished !
I use an Ardupilot and display it on the TX LCD on 10 screens (all backlight)
No external things hanging out !
All internal in the 9x.
Plus I have an autopilot with GPS, waypoints, stabilization, auto mode, takeoff/landing, and more to come.

Pic 1 is latitude/longitude ......great for lost plane
Pic 2 stuff that goes in plane
Pic 3 xBee 2way telemetry unit in er9x.

Looks really cool with 2 antennas too !

Put FPV video on plane and you have a UAV that costs less than a USED Reaper (if you could get one)
Cost ??? about $300.00 Is YOUR plane worth it ?
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  • I wonder if it would be possible to use one of the PPM RC channels for uplink capability.  My hypothesis is that on an xbee setup, the downlink uses most of the bandwidth for realtime GPS position and attitude, etc.  The uplink is used mostly to send commands (i.e. updated waypoints, or mode change). 

    The hurdle is to mod the hardware to allow the PC to control an RC channel directly, without the RC Tx getting in the way (or maybe just hook up er9x to USB during flight?).  Then the software for Mission Planner and the APM firmware itself would need some code to add the new features...

  • That's clear, thanks for explanation!

  • The xBee connects to the mosi and moso pins on the cpu in the er9x tx. that is the tx and rx lines. you must reprogram the er9x tx with the firmware I referred to a few posts up. It does take some soldering, or as an alternitive there is a programmer and backlight that just screws onto the ckt board with spring loaded pins to make connections. You then can solder the xbee tx rx to this board. Read up on the er9x firmware mod...



  • Earl, could you tell more, please, about connection and communication with LCD?

  • I would like someone to help me do a version for mavlink. This version is legacy only. It's been a while sense I was programming. It's in 'C' like language.


  • Xbees can do point to multipoint. It took me a while to fugure it out tho.

    The coordinator xbee DH = 0 and DL = FFFF also the CE = 1 This goes in plane.

    The end point xBee(s) CE = 0 and DH DL = address of xBee in plane.


    Now my er9x recieves the data ANDound station ALSO recieves the data.

    It took me several days pouring over digi's data info and searching the web.

    So thats how point to multipoint works. (at least for me)


    The code is programmed into the er9x. Follow this thread. I wrote the ardupilot section.


    Neat !! Especially with the 2 antennas on TX


    I bought mine a yeaHK. They don't stay in stock. They go like hotcakes! There is a place in US that sells them and they are generally in stock but the price is $89. Still a good deal.


    Programmer from Sparkfun for $15.



  • I bought that same FS ($89) from There selection is not the greatest, but unlike HK, they don't tease you in with out of stock, or only "international" items.
  • Admin


    The 900MHz Xbees and really designed for point to point. Why are you using them in the Mesh mode?



  • Moderator

    Great work, i was wondering where you bought your er9x from?  I know you can get them from HK (turnigy version) but they are always out of stock

  • Legacy now. Working on mavlink.!

    900 xbee for longer range.

    program the xBee's one as coordinator and other ones as endpoints make coradanator to add dh 0 and dl FFFF

    this goes in plane

    the ones on ground in tx are end pointes with the hi and low address of the plane.

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