PPM error detection

[rblilja]

Hi, a question..

Which method is the safest way to detect the loss of transmitter signal, when reading a PPM output from a RC receiver? My reading function extracts the corresponding servo pulses, and detects the sync pulse. What I need is an algorithm telling weather the PPM signal is ok or not.

My only check is the lengths of the pulses; if they are out of bound I skip them.

My platform is an ATMega168, using C. Reading the PPM with the input capture unit.

Thanks for any advice.

// Robin Lilja

[pitlab]

Which method is the safest way to detect the loss of transmitter signal, when reading a PPM output from a RC receiver? My reading function extracts the corresponding servo pulses, and detects the sync pulse. What I need is an algorithm telling weather the PPM signal is ok or not.
My only check is the lengths of the pulses; if they are out of bound I skip them.

In my project i have available signal from one receiver channel. I check 2 things:
- length of the pulse if in range 0,8 - 2,2ms
- time between next pulses if in range 10 - 30ms

When distance is close to out of range the additional pulses can occur. Also signal is unstable (servos buzzing). You can detect stability of pulse time (servo way) between next pulses. If it is smooth then ok, if has noise, then is wrong.

[rblilja]

Ok, thanks. The advice of extra pulses occurring where new to me.