Hi Folks,
I currently try to read a PPM signal with an Arduino (Nano v3) for further processing in a Quadrocopter.
Setup:
- Nano V3 supplying RC-Receiver
- they share a common ground
- using inerrupt pin D3 on nano with signal line on arduino
- Turnigy TGY-i6 + iA6 AFHDS 2A
- Turnigy TGY-i6 + FlySky FS-R6B AFHDS
What I basically do is:
onInterrupt(){
readPPMAndCalculateThrust(); //values between ~1000 to 2000
}
loop(){
readSomeSensors();
calculateThrustForEngines();
updateEnginesThrust();
}
Problem:
The signal has random really large peaks (see attachement). I already tried dozens of implementations for reading PPM signals by interrupt and every implmentation is facing the same problem.
Semi-Solution:
At the end of my loop I added a routine to have a constand round-trip-time.
//ensure desired round trip time is not too tight
if(millis() - start > RTT)
abort("RTT to small");
//wait
while(millis()-start < RTT)
delay(1);
Seems like the interrupt cannot go together with 1ms delay. I changed it to delay(5) and it's working perfectly with some minor glitches which can be filtered easy.
Update:
I tried waiting the remaing time at once delay(RTT-millis()+start); wich brings up my old problem. So I'll stick to delay(5) - still don't know whats causing this 
Regards,
BlubBlubClub
