Hi all,

I have this weird problem that has been bothering me for days and don’t know how to solve.

I’ve been building a 3.5 inch quad and I have a happymodell EP2 ELRS receiver which when I have soldered on my Speedybee f7 mini stack FC & ESC.

On the transmitter (Radiomaster Zorro) it appears to be connected.

On the receiver I can see that it blinks normally before I turn on the transmitter and then it stops blinking once the connection is made.

This connection now sometimes works and sometimes it doesn’t (mostly doesn’t). Basically I move the sticks and see them changing in the receiver tab in Betaflight.

Because of not being able to connect every time I cannot fly my quad.

I have tried the following:
1. Desolder and resolder the receiver and change cables
2. Try different uarts
3. Try a different receiver (3 Happymodel ones and 1 Matek)
4. Upgrade to ELRS 3.0.0 and downgrade again in both tx and rx and also flash them

Any suggestions on what to do here?

You seem to have tried several things so far.

Out of curiosity, are you testing this on the bench?

What output power is the TX set to?

I assume you have tested at a distance of more than a few meters away from the quad as being too close to the quad at times can cause issues.

Use it on a simulator.. see if it persists there…

(17-Sep-2022, 02:21 PM)Rob Axel Wrote: Use it on a simulator.. see if it persists there…

Hey Rob,

I tried and it works but I suspect it is because the data go through USB and not the antenna.

I can see on the screen the controller's stick values changing when I move them but it seems that they do not appear in the receiver tab in Betaflight nor the quad arms / allows me to control it at all.

(17-Sep-2022, 10:57 AM)kafie1980 Wrote: You seem to have tried several things so far.

Out of curiosity, are you testing this on the bench?

What output power is the TX set to?

I assume you have tested at a distance of more than a few meters away from the quad as being too close to the quad at times can cause issues.

Yes testing on the bench. Have tried being 1-3 meters away from the quad but makes no difference.

In regards to the TX power, I have tried anything between the minimum 10 to max 250mW.

Even tried being in a different room and sadly it makes no difference.

the sim was to check ur gimbals.. any chance u may have another quad or Rx nearby?

(17-Sep-2022, 05:02 PM)Rob Axel Wrote: the sim was to check ur gimbals.. any chance u may have another quad or Rx nearby?

I have another quad yes. Same problem there. The receiver appears to be connected but no stick input in Betaflight.

Simple process of elimination … apparently it’s ur controller..
I’m curious if a external module would help salvage the controller..

(17-Sep-2022, 05:08 PM)harrisgeo88 Wrote: I have another quad yes. Same problem there. The receiver appears to be connected but no stick input in Betaflight.

I've been thinking the same. Is there a way to see what data my controller is sending so that I 100% confirm it is the controller?

You can't easily test the over-the-air data transmission but there there's a channel monitor page in EdgeTX with bars on where you can see if the sticks are actually sending output to the transmitter module inside the radio, so you can at least check that. Just go to that page and wiggle the sticks / move the switches to see if the bars move.

Do you happen to know anyone else with a known working ExpressELS transmitter or module? That would be the easiest way to try and confirm or rule out an issue with the hardware in your own RadioMaster Zorro.

(18-Sep-2022, 09:31 AM)SnowLeopardFPV Wrote: You can't easily test the over-the-air data transmission but there there's a channel monitor page in EdgeTX with bars on where you can see if the sticks are actually sending output to the transmitter module inside the radio, so you can at least check that. Just go to that page and wiggle the sticks / move the switches to see if the bars move.

Do you happen to know anyone else with a known working ExpressELS transmitter or module? That would be the easiest way to try and confirm or rule out an issue with the hardware in your own RadioMaster Zorro.

I'm meeting some friends today and we'll find out there for sure if it is the transmitter or not.

In regards to your mention of the channel monitor, I did some search and found this guide on how to add live telemetry readings.



I can see that the options for pitch, yaw and roll that do not change at all which makes me think that this is the problem.

Thank you for guiding me to finally finding that. I'll respond later today if my friend's controller worked.