Help with PPM Configuration on RFD900x 2.0 and TXMOD 2.2

Hardware Radios
1

Hi everyone,

I’m trying to configure the PPM output of the RFD900x 2.0 with TXMOD 2.2 to eliminate the need for a separate RX. I’ve completed the basic setup using the wizard, but I’m stuck on how to properly configure PPM.

My Goal:

  • Utilize only the RFD900x for both tlm and PPM output.
  • Control a plane using the RFD900x’s PPM output.

What I’ve Done:

  • Completed the basic RFD900x configuration through the wizard.
  • Enabled PPM output in the RFD900x settings.

What I Need:

  • Detailed instructions on configuring PPM on the RFD900x and TXMOD 2.2.
  • Information on which parameters to configure in TXMOD for proper operation with the RFD900x’s PPM output.
  • Troubleshooting tips in case the PPM output isn’t functioning as expected.

Any assistance you can provide would be greatly appreciated.

Thank you in advance for your help.

Best regards

2

Use this guide

and use SBUS if possible, but you can substitute PPM if you really need to.
SBUS has the advantage of signalling a failsafe in the serial data instead of relying (only) on throttle below failsafe (and channels going to values set when the “PPM failsafe” button was clicked)
SBUS is a serial protocol with RSSI info and other things contained within, where PPM is more like old fashioned PWM.

2 Likes
3

Hi, thanks for the tutorial, I followed it and it does not work, I am measuring the signal with my toolkitrc charger that has sbus measurement function. the only thing that I think may be wrong is the refresh rate that as seen in the picture I can not go higher, as you indicate in the tutorial, what can I do? I have a TX16S with edgetx.

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4

Maybe show some screenshots of your TXMOD and RFD900X settings
and your wiring.

On my TX16S/EdgeTX the refresh rate is 7.0ms (normal)

5

This is how I have my setup, and the wiring I am using for testing is 2 and 4 for power and 15 for signal output.

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6

The only real difference I can see between mine and yours is S26:AIR_FRAMELEN 4000 should be 120
Mine is at default and I’ve never changed it.

I’ve also set S13:RTSCTS 0 since the screenshots were taken for that little tutorial, which is how your is now too.

7

Hello again, I haven’t managed to get the SBUS to work, I added the configuration files for you to compare, and copy as your same configuration and also I added the original basic configuration, I hope you can help me.

I hope you can also tell me how to reset or delete the configuration to do it again from scratch.

Original_params.txt (603 Bytes)
Original_params_remote.txt (605 Bytes)
r900x_params.txt (582 Bytes)
r900x_params_remote.txt (580 Bytes)

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And so I have the connections for testing.

8

I cant see an issue with those settings. Do the radios show as connected with a solid green LED?
In my TX16S the refresh rate is 7ms

The latest RFD900x firmware:

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The latest TXMOD firmware - it is made up of two parts, the V2.11.bin and the spiffs357.bin files.

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Do you have a ground (0v) wire from the RFD900x (SBUS output) to the charger SBUS input?
Pin 16 is a convenient ground.

Are you planning to use this with a flight controller? I would connect it all up including the data wires and see what the flight controller says.

To reset the TXMOD find the blue button and press it 5 times rapidly.
To reset the RFD900x you need to connect it via the FTDI/USB cable and use a terminal program to send AT&F to reset all to factory defaults. Check the pdf manual for entering AT command mode and other commands. Your terminal baud rate has to match what the radio is set to.
I’ve never had to reset an RFD900x - I can always connect with some baud rate and set what I need.

9

thanks, I’ll try to put another ground to the receiver, and yes I already put 7ms in the tx16s, both are updated, the green led is fixed and yes, I will use the FC CUAV V5+.