[dkustec]

Hi, guys.
There is a new moment with my OPLM (Rx side) which is binded to OPLM on Tx side.
I Have 9x TX connected with OPLM on PPM bus. On vehicle side, there is OPLM binded to 9x and all works as a charm. Channel 9 is RSSI info and all works normal. Until Rx lost connection (when Tx is connected and then turned off. I didn't try what's happens when is signal out of range). When the Tx is switched ON again, Rx OPLM binds on it, BUT - through 2-3 seconds, there are all PPM max values on ALL channels, except channel 9 (RSSI). This is so strange and might ne dangeorus, because there is a chance that FC will arm and jump on full throttle (this happens to me several times, but fortunately with no props). These values are pulsating and in worst case - there is a great chance that the vehicle will be armed and then full thrusted.
So, I inverted output of ARM switch on 9x just to be sure that there is no possible combination for arming.

All of this is happens on Betaflight, but - I think that is not a behaviour of the FC but the OPLM. Is this bug or something?

[TheOtherCliff]

That sounds like an OPLM bug.  It is hard to say whether it is on the Tx side or Rx side.

While the Tx is turned off, does it produce no signal?  For a short time during startup  (in between Tx off and Tx on with good signal) it produces max on all channels)?

@f5soh would be the one to answer this, I think.

[f5soh]

Please test using the firmware attached and see if something changed.

[dkustec]

Nice work,  f5soh Now, it is all reversed when Tx is turned off and this is the way to go. Now, there is no chance for accidentally arm and full throttle. Thank you so much!

Is it possible to put RSSI channel (9) when Tx is disconnected on min value, also? I'm just curious.

[TheOtherCliff]

Hmmm...

It really should have "no output" while it is connecting.  I hope these displays are just BetaFlight's display when there is no output, or this is a special firmware just for you. 

It's not good if it is actually outputting those mins instead of true transmitter stick positions.  Imagine a fixed wing in Manual mode suddenly doing full controls at high speed.  Imagine a transmitter where low signal means high throttle.  Also the flight mode jumps to position #1, even if all failsafes and the transmitter switch are elsewhere.  This would glitch when it switches from OpLink "out of range" to normal flight, even if the FC failsafe stick positions and the transmitter stick positions are the same.

[dkustec]

TheOtherCliff, yes, you are right. In the best scenario those PPM values should be exact same as before Tx was disconnected. This custom fw is good to me (and others who want oplms to use with BetaFlight), but in your case it is absolutely unacceptable.

In BetaFlight, whenever is "no-signal", PPM values are 1500 us default for sticks, except the throttle which is 885 us, and last known values for other channels. Unfortunately, I did not test what is going on when is Tx out of range, yet.

[Brian]

The OPLink should be going into failsafe mode when a PPM signal is not detected on the Tx side, which should cause the Rx side OPLink to not output any PPM signal.  I believe that's what it shows in the "Disconnected" picture.  What I don't understand is why it is different in the "Connecting" picture.  The Tx side should not be receiving a valid PPM signal, so the Rx side should go into failsafe.

F5soh, did you find some place in the code where it is not going into failsafe?

[dkustec]

Hm, maybe, problem is in connection with 9x and OPLM on Tx Side? Maybe Turnigy 9x floods his Tx OPLM with PPM signals when it's powered on? I will try to remove PPM connecton from Tx station and leave just vcc & gnd connected on Tx OPLM. If nothing happens on Rx maybe is problem only in Turnigy.

[dkustec]

Attached is the picture what happens when Tx is powered on, binded to Rx and with no PPM wire connected to Turnigy PPM connector.

[TheOtherCliff]

I think that @f5soh made this code specially for this user.  This code puts RSSI on channel 9.  Note that the RSSI value is not min or max.  It may be the new(?) RSSI addition always puts RSSI on PPM even if the other PPM channels don't have good values.  Just guessing.

[mr_w]

@TheOtherCliff

This is LP-520 PR, still pending for merge, so I guess any problems (like disabling PPM output in case of complete loss of connection) will be addressed in time.