Turnigy 9x / FlySky 9x FrSky Mod

The instructions below illustrate how to use an FrSky ACCST radio module in a Turnigy 9X remote. Unfortunately these two systems are just “almost” compatible, a little mechanical intervention make them completely compatible. We can just hope these two manufacturers learn to collaborate.

This is the setup: A Turnigy or FlySky 9x without TX module, a FrSky transmitter and receiver kit (the bundled 8 channel receiver will not be used) and the FrSky D4R-II PPM sum receiver.

Note that the D4R-II outputs only four channels on its connectors, but does support 8 channels in CPPM mode. There is no need to carry the additional weight of an 8 channel receiver.

Unfortunately Turnigy / Flysky decided to make it hard to use other transmitter modules by putting a small plastic emboss in place. The task is to remove this, to make the FrSky module fit well.

Put the transmitter on its top side and unscrew all screws with a Philips PH0 size screwdriver. NOTE: if you are really good and careful with a knife, you can skip this step and carve away the plastic directly.

Open up the receiver, unscrew the four screws holding the back printed circuit board in place. Pull it gently 1 cm / 0.5 inch inside the case, so that the pins protruding into the TX module bay are not any more prodtruding.

Cut the plastic emboss with a cutter. It does not need to be a clean cut, it just matters that the top 1-2 mm are gone.

Put everything back together. Plug in the TX module.

The recommended battery type are low self-discharge types, such as Sanyo Eneloop. Put them into the battery tray.

Only the FrSky D4R-II receiver (and the D8R-XP not shown here) can output CPPM. The bundled 8-channel receiver can only be used for manual flight or with a PPM-encoder.

Flashing the Er9x with OpenTX

The default firmware can be replaced by OpenTX using for instance this Programmer.

Hardware Instructions here

To flash the OpenTX firmware, it's easiest to use OpenTX Companion.

To download the latest firmware, go into File → Preferences and click Check for updates.

Then, choose Burn → Write Flash memory and choose the hex you just downloaded.

After flashing the firmware, you can optionally flash the EEPROM using this settings image which will set everything to Mode 2 and AERT (aileron, elevator, rudder, throttle) and configure 4 more switches including the 3Pos switch.

Finally, switch on the the remote and do the calibration of the sticks because this varies over different transmitters. Additionally, the battery voltage should also be calibrated.

Upgrading the D4R-II Firmware

The FrSky default firmware contains an issue when more than 5-6 channels are used in CPPM mode. This can be solved with a fixed version provided by FrSky.

Use the cables from the D4R-II packaging and from the FrSky USB adapter packaging to re-assemble this new cable. To do this, lift the plastic levers holding the individual pins in place and re-plug them accordingly.

D4R-II flash cable

Now download the FrSky Firmware (including Upgrade Tool and instructions):

Pairing the Transmitter / Receiver

Please follow the pairing instructions carefully and test the failsafe behavior in case of radio loss prior to flying

If the radio connection between an FrSky transmitter and FrSky receiver is lost, the FrSky receiver will output the values which are active while pairing.

The PX4 firmware will detect the loss of radio only when the throttle channel is lower than the calibrated range (not implemented yet). Therefore the receiver must be paired with the throttle at its lowest possible value. After pairing, the throttle range can be changed so that the lowest value is around 100 us higher.

Instructions for OpenTx

1. Set throttle range to 100%
  1. Go to the MIXER settings (press - long and go to page 5/9 using +/-) and look up to what channel your throttle is set (default channel 3)
  2. Go to the LIMIT settings (press - long and go to page 6/9 using +/-) and verify that the range of the throttle channel goes from -512 to 512 like by default

2. Pairing
  1. Switch off transmitter and receiver
  2. Switch on transmitter while pressing the button on the FrSky sender module. The sender module should keep beeping now.
  3. Switch on the receiver while pressing the button. It should keep blinking red but also the green light should blink very fast.
  4. Now switch both, transmitter and receiver off
  5. Switch both devices back on. The receiver's red LED should be off the green LED should blink very fast.
3. Reduce throttle range to 90%
  1. Go to the LIMIT settings (press - long and go to page 6/9 using +/-) and set the range of the throttle channel to -450 to 512

4. Do RC calibration
  1. Open QGroundControl and connect to your autopilot.
  2. Open the tab Config and go to Radio Calibration, then follow the instructions
5. Check RC failsafe
  1. Open QGroundControl and connect to your autopilot.
  2. Go to the tab Pro → Plot and check the value of RC_CHANNELS_RAW.chan3_raw. Make sure it drops when you switch off the remote.

Instructions for stock Turnigy firmware

FIXME: please add this

Setup Switches

Using openTX (or er9x)

The start screen should look more or less like this. If not you can change the view using the +/- buttons. Make sure all the switches work. They should get highlighted, when you switch them towards you.

Now press the - button long to get to the menu of the current model (containing 9 pages). Go to page 5/9 (Mixer) pressing -.

Go down (DN button) to channel 5 (CH5) and press MENU long.

For channel 5 choose the 3POS switch. Leave the menu using EXIT.

Note that channel 5 should always be the mode switch. For channels 6, 7, 8 you are free to choose what switches you want to assign. Below is the recommended setup.

Do the same for channel 6, 7, 8:

Now the Mixer overview should look like this:

Using the stock Turnigy firmware

FIXME: Instructions how to setup the switches on the stock Turnigy firmware are lacking. Maybe this post on diydrones could help.'

The recommendation is to use the open source openTx firmware. Instructions how to flash the remote can be found here.

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