/elec/quadcopter

//

// main.ino

//

// Testing reading from the receiver.  We're expecting a PWM signal, on

// interrupt 0 (which is pin 2 on an Arduino Uno).

//

// This program tries to measure the width of the signal pulses in

// microseconds.  It takes several measurements and prints it the average over

// serial.

//

// number of signal pulses to average (for damping)

#define DAMPING_SAMPLES 1

// set to the time that the last signal pulse was at

static unsigned long _new_pulse_on = 0;

static unsigned long _new_pulse_off = 0;

// ISR to handle the PWM signal

void signal_handler()

{

	// record time

	if( digitalRead( 2 ) )

		_new_pulse_on = micros();

	else

		_new_pulse_off = micros();

}

void setup()

{

	// set up an interrupt handler on pin 2

	attachInterrupt( 0, signal_handler, CHANGE );

	digitalWrite( 2, LOW );

	Serial.begin( 9600 );

}

void loop()

{

	unsigned long last_pulse_off = 0;

	unsigned long intervals[ DAMPING_SAMPLES ] = {0};

	int interval_idx = 0;

	while( true )

	{

		// detect pulse falling-edge

		unsigned long pulse_on = _new_pulse_on;

		unsigned long pulse_off = _new_pulse_off;

		bool got_pulse = false;

		if( pulse_off > last_pulse_off )

		{

			// sanity check

			unsigned long interval = pulse_off - pulse_on;

			if( interval > 800 && interval < 3000 )

			{

				// update interval buffer

				intervals[ interval_idx ] = pulse_off - pulse_on;

				if( ++interval_idx >= DAMPING_SAMPLES )

					interval_idx = 0;

				got_pulse = true;

			}

			last_pulse_off = pulse_off;

		}

		// display average?

		if( got_pulse )

		{

			// calculate average

			unsigned long ave = 0;

			for( int a = 0; a < DAMPING_SAMPLES; a++ )

				ave += intervals[ a ];

			ave /= DAMPING_SAMPLES;

			// tell it like it is

			Serial.print( ave );

			Serial.print( "\r\n" );

		}		

	}

}