PPM encoder is not rebooted by reset switch neither USB connection.


I've seen many times that when rebooting the board, or connecting the APM +5V rail when connected through USB, we can loose CH1 or 2 or 3 or 4 input.


This is caused i think by a PPM encoder crash because of noise or spikes on the +VCC rail.


Eventually the PPM encoder could be crashed by the main AVR reboot noise.


After watching to the APM schematics, it seems that the PPM encoder reset is not connected to the reset switch, neither to the USB reset output.


To avoid problems, i think that the PPM encoder reset input should be connected to main board reset circuitry so that it is resestted at the same time when USB connection is done or when manualy reseting the board.


Perhaps that the USB +5V shoud not be used as well, to avoid power spikes when connecting USB and crashing the PPM encoder.


Those PPM crashes could explain why some users do have strange radio behavior sometimes.


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I've reopened issue 157 i've opened 2 weeks ago in the tracker, as i feel now that it is not a specific problem on my board.



Thanks for the report. We'll look into it.


I will check tomorrow with a scope what's going on on PPM and MUX lines during the problem. Should be quite easy as i can reproduce quite frequently.


I feel that during main AVR reboot, it is crashing the PPM encoder through PPM or MUX lines shorts.


Perhaps that the solution could be a green wire between a main AVR output and the PPM encoder reset line, so that you can trig a PPM encoder reset after main AVR boot.




Thanks for the info... It will be considered for the next revision.. =)



    I'd be interested to see a green wire patch if you can give it a try.  On the trad heli I get some jumpiness in the servos when resetting the board (usually on the first channel).  It's not terrible but it would be nice not to have.



The green wire patch is easy to do, but what you see does not come from here and it will not solve it. So i prefer not to give it. It seems that the problem i have with the PPM encoder is specific to my board. I'm waiting a replacement board.


The PPM encoder is responsible for inputs, not outputs.


To solve your problem, a new bootloader or eventually pre boot code needs to be installed on the main AVR chip. This will certainly be done as soon as the team will go out of the beta phase so that they can have time to do this.



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