Build Log: Taranis and TBS Discovery Pro, Part 3

In the third part of the build log I would like to cover the setup and configuration of the Taranis RC with the TBS Discovery Pro. After covering the mechanical build in part 1 and part 2 of the build log, this part will be about the wiring and programming of the remote control. Due to a crash I’ve build the copter a 2nd time.


Detailed setup guide and model files to download after the break.

Together with the Discovery Pro I also needed to buy a new RC controller, as I did not have any. When looking around for 2.4 GHz controllers in summer 2013 the Taranis from FrSky offered very competitive features, for a very affordable price. Specs wise, none of the established brands (Futaba, Graupner) could offer anything comparable in the price range of 200$. On the other hand, the Taranis was brand new, hardly available and with questionable reputation despite positive reviews. Do I want to trust a cheap RC to control my expensive copter? Why Not! No risk no fun;) And so far, the Taranis is a very positive experience for me.

Wiring-up the components

The wiring on the Discovery is built into the frame giving it a very clean appearance. The X8R receiver can output different signal types. Simultaneously you can have multiple channels on the S.BUS in a single connection and eight channels as individual PWM signals. The Discovery pro needs up to 10 channels in total for three independent systems. I use the following signal types.

  • S.BUS for the 7 channels of the Naza flight controller
  • PWM for the 2 channels of the gimbal (pan/tilt)
  • PWM for the 1 channel of the core to switch the camera

Before you can use the X8R receiver, you need to bind it to the Taranis. In order to use all the channels you also have to change the receiver mode to Mode 4 (D16). The factory settings is for 8 channels only. This procedure involves using 2 jumpers as described in the X8R manual or in my step-by-step instructions. In Mode 4, the physical PWM connectors labeled 1,2…8 are assigned to CH9,10…16. On the Disco you find eight channel inputs labeled 1,2..8. I connected the in the following manner:

  • Discovery connector 1 to X8R connector S.BUS, for the Naza
  • Discovery connector 5 to X8R connector 1, for gimbal roll
  • Discovery connector 6 to X8R connector 2, for gimbal tilt
  • Discovery connector 8 to X8R connector 3, for the camera switch
Backend of the Discovery Pro with the FrSky X8R receiver and the two PCB antennas.
Backend of the Discovery Pro with the FrSky X8R receiver and the two PCB antennas.

Programming the Taranis

On the Taranis I configured a very basic setup. It only covers the barebones needed for flying and controlling the gimbal. I have a mode 2 Taranis (throttle on the left), so the setup of the 2 main sticks are:

  • CH1: Ail
  • CH2: Ele
  • CH3: Thr
  • CH4: Rud
  • CH5: …unassigned
  • CH6: IOC (added in v1.1)
  • CH7: Is for GPS/Atti/Manual (Fail Safe). Which I assigned to Switch SD.
  • CH8: Is unused by the Naza. But S.BUS needs to transmit all 8 channels in bulk.
  • CH9: Gimbal Roll on S1
  • CH10: Gimbal Pitch on S2
  • CH11: Camera Switch on SF

Some remarks

I don’t use the X1 Naza channel so far on CH5, therefore I did not assign it to any physical controls, but it only needs to be setup in the Taranis and the Naza in order to work. I chose the location of SD on CH7 on the top right similar to the DJI Phantom RX. I can not actively trigger fail-safe with a dedicated switch. However, when the RX looses connection, it does signal Fail Safe through some S.BUS feature. Please check if Fail Safe works with the Naza configuration software before your first flight. Confusingly, S.Bus is named D-Bus in the Naza Software.

Download my model file

Please feel free to download the model settings for your Taranis. I’ve prepared two different formats. Unzip them before use.

  1. [disco]  This .bin model file can be loaded directly by the Taranis. It has to be copied into the ‘MODELS’ directory of the SD card residing inside the Taranis. Then you can navigate to an empty model slot, long press ‘ENT’, select ‘model restore’ in oder to copy the ‘disco pro’ from the SD card to the Taranis.
  2. [Disco Pro for] This .eepe model file can be loaded by the companion9x software with your PC or MAC. I’ve tested it with version 1.51 which you can find here. This way you can first look at the settings in the simulation software and then flash it to the Taranis.

The model can also be found on Good luck and let me know how it works for you.

Changes  in V1.1  (AUG-10-2014)

  • Inverted ELE and THR to match the stock settings of the NAZA. If updated from v1.0, please change the settings in the NAZA (untick the ‘reverse’ on these two channels). If you use this model fresh with a Naza, do a stick calibration.
  • Added IOC control (SA switch on top left)
  • Added expo curve on Rud when SB is switched to center position. This reduces yaw angle movement and makes panning smoother during filming.


19 thoughts on “Build Log: Taranis and TBS Discovery Pro, Part 3”

  1. Great blog!
    I am using the Taranis on my Disco PRO with EzUHF.
    I am a bit confused reading through this. I am struggling to set my GoPRO-FPV Cam switch to work.
    I am using PPM on channel 1 for the Naza and the Gimbal Pitch and Roll. The second cable is on Channel 8 set to PWM in my RX.
    How do I set the RC to give PWM signal on channel 8. I think at the moment I think Channel 8 works as PWM.

    1. Hi Daniel,

      To be honest, I don’t know too much about ExUHF, so I can’t comment on how to setup the RX to output PWM and PPM simultaneously. Besides the RX you could check some of the settings:

      • Taranis: Make sure CH8 changes from a value bellow to above 50% (center point). E.g. assign a 2-way switch and give it a weight of ~100. See my model file (.bin).
      • Taranis: Check if you output on all eight channels. It’s possible to use an 8 channel mode, but only send data on 7 (e.g. without the camera switch)
      • Disco Pro: flip the “CAMERA TYPE” to “SWITCH” in the onboard TBS core video menu. Use the little buttons on the top-plate and look at the on-screen menu in the video downlink.
      • For testing and debugging you could use a different channel (not CH8) an use it for two copter functions simultaneously. E.g. CH6 for the gimbal (PPM) and the camera switch (PWM). This way you have visual feedback (gimbal position) and if everything else is correct, the camera should switch at the midpoint of the gimbal rotation.
      • GoPro and onboard camera (TBS69 ?) have to use the same video system (PAL or NTSC). You can change it on either side. If they don’t match, the video sync can get lost and you see nothing.
      • Hope this gives you some more ideas how to test.

  2. Hi again! Sorry for the very very late reply 😛
    I followed your advice and good thing I did! After I tried everything on earth I could! I started debugging as you advised.
    aaaaaand that’s! when I realised the bloody lead cable from channel 8 was not conducting. Changed the cable and it’s all good!

  3. I am trying to set up all normal Naza stuff as well as Gimbal controls etc but dont understand the Taranis or Radios enough to work out why if I select CH6 and assign it to S1 it doesn’t work.

    Wondered if you would be able to sort out a few questions with regards to assigning things to PPM and PWM, what are they and how does it work and how do you assign it to a channel?

    Ideally I would like everything working, IOC, GPS/ATTI/FS and standalone FS switch and also the ability to switch cameras (as I have a TBS Disco Pro) and also control rool and pitch.

    Thanks in advance.


  4. Did you have to change your settings in the gimbal software to PPM or did stock settings work? Great blog!


    1. I’ve never used PPM for the gimbal control because my receiver FrSky X8R has no PPM output.

  5. Daniel, I noticed your using your taranis and ezuhf for your pro. I’m doing the same thing. Would be able to share your file with me? I’m still trying it figure this radio out

  6. Hello,

    thanks for your report about the Disco pro setup. I just did the same and use your Disco and Taranis Setup (TX Mode 4, RX using your *.eepe file).
    NAZA connection worked as it should be.
    But the gimbal is not effected by S1 and S2. No pitch and rolling but with one exeption: when switching SD to middle the gimbal piches up.
    X8R RX is connected: ch 1 to sbus, ch5, ch6 gimbal pitch and roll, ch8 cam switch (as written on the frame) The gimbal Software has never been touched and no extra solder poinds on the board has been shorted (ppm gimbal). Any hints from you would be perfect.



    Greetings out of germany

    1. Hi Norbert

      It should work out of the box without touching the gimbal software or changing any solder points. Your description of the problem is strange. SD switch is CH7. It is not fully clear to me, what is wrong and how you managed to connect the gimbal to CH7. But maybe try:

      1. check the 4 cables between the X8R and the Disco frame. You do not say, where you connect the cables on the RX side. They go into the connectors 1,2,3 and S.BUS. The cables are all together on one side of the X8R. S.BUS goes to Disco1, X8R.1 goes to Disco5, etc.
      2. Check the mode4 settings once more. If the gimbal moves with your sticks (Ele, Ail, The, Rud) then the mode is wrong.
      3. Maybe my eepe file is wrong. The epee file was made with a 1.x firmware Taranis and a slightly older Companion software. Maybe there is something wrong here. Maybe try the .bin directly on your SDcard and a model restore.

      Good Luck!

  7. Hi crashpilot,

    meanwhile i managed to set up my Disco Taranis Combo as wanted. the Problem seems to be the binding process.: I forgot to take away the Jumpers before reconnecting the x8r to the power after binding. Now it works like it should be.
    If you have some add on to the profile like e.g.
    – circling around a point of view
    – add a dedicated FS Switch
    just sent me a note.

    Thanks and greetings out of germany


  8. Hi,

    Thanks for taking the time to put up a very useful blog. I haven’t assembled the Disco Pro yet, I’m studying thing while I wait for delivery. I see you set up channel 7 as flight mode, but I =can’t seem to find an “RTL” functon in your model (other than turn the Tx off to force failsafe). Did I miss it? Can shed some light on this, as I’d like to be able to hit “RTL” even if the Tx did not fail. Please bear with me, I’m very new quads, Naza, Taranis, the whole 9 yards. Have been flying RC for decades, but this new stuff is all …well, new. 🙂

    1. Hi Bruno,
      You are right, v1.1 oft my model file does not include a dedicated F/S switch where you could trigger return-to-home. Turning off the Taranis is your only option at the moment. I might add it in the future. For now I can only recommend you to get some inspiration from a more feature loaded Naza model file.

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