Sunday, April 2, 2017

An AVR ATmega R/C control signal reader - Method/01

The Radio Control (R/C or RC) is the method of controlling remote devices using radio frequencies.
Most of the time the RC signal uses RC servo signals.
Servo signal is a square PWM signal, usually with a period of 20ms and a duty time between 1ms and 2ms. More info on the wikipedia page here:

This library implements a method to read an RC signal and eventually map this to a 0..100 number.

It's developed on an ATmega8 running at 16Mhz.
It makes use of the external interrupt PIN and a timer to count the duty period time.
It's customizable to fit the user preferences. Configuration can be found in rcin1.h header file.
Theory of operation: each time a rising edge interrupt it is raised, a timer starts counting until the falling edge happens. Then the number of ticks counted between interrupts is transformed to us spent in duty time.
Input PIN is INT0.
The RC signal it is measured and then mapped to a speed value from 0 to 100.

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