Leftyretro
New Member
No, your mistake. I was talking about the so-called 'PPM' signal used to modulate the RF signal.
For a constant frame rate, the signal going to the servo is PWM.
While it is a form of PWM, Nigel's point is valid. Most micro's hardware PWM modules aren't designed well for emulating the decoded PPM signal that a standard servo is designed to accept. If the PWM hardware is set up for a 20 millsec period (frame refresh rate) then the 0% (1msec) to 100% (2 msec) servo travel represents a duty cycle range of only 5% to 10% of the total duty cycle range. This doesn't allow very good resolution as the full duty cycle resolution has to be able to cover 0-20mec. So in a 10 bit duty cycle PWM module only around 50 'counts' will be avalible for the actual servo travel and that's not very good resolution, effectivly only about a 6 bit resolution, OK for some applications, but a servo is capable of better.
That make sense or have I got it all wrong?
Lefty
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