/elec/quadcopter

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//
// 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 frequency of the signal pulses in
// microseconds.  It takes several measurements and prints out the average over
// serial.
//
// NOTES: This test is not very useful.  Our second experiment was measuring
// pulse width (../pulse-width).

// number of signal pulses to average
#define SIGNAL_SAMPLES 10


// set to the time that the last signal pulse was at
static volatile unsigned long _new_pulse_at = 0;


// ISR to handle the PWM signal
void signal_handler()
{
	// record time
	_new_pulse_at = micros();
}


void setup()
{
	Serial.begin( 9600 );

	// set up an interrupt handler on pin 2
	attachInterrupt( 0, signal_handler, RISING );
}

void loop()
{
	unsigned long last_pulse = 0;
	unsigned long intervals[ SIGNAL_SAMPLES ] = {0};
	int interval_idx = 0;

	while( true )
	{
		// detect pulse
		unsigned long new_pulse = _new_pulse_at;
		bool got_pulse = false;
		if( new_pulse < last_pulse )
			last_pulse = new_pulse;
		if( new_pulse > last_pulse )
		{
			// check interval
			unsigned long interval = new_pulse - last_pulse;
			if( false && interval < 300 )
			{
				Serial.print( "[" );
				Serial.print( last_pulse );
				Serial.print( "," );
				Serial.print( new_pulse );
				Serial.print( "]" );
			}
//			if( interval > 19000 && interval < 20500 )
//			{
				// update interval buffer
				intervals[ interval_idx ] = interval;
				if( ++interval_idx >= SIGNAL_SAMPLES )
					interval_idx = 0;

				got_pulse = true;
//			}

			last_pulse = new_pulse;
		}

		// display average?
		if( interval_idx == 0 && got_pulse )
		{
			// calculate average
			long interval = 0;
			for( int a = 0; a < SIGNAL_SAMPLES; a++ )
				interval += intervals[ a ];
			
			Serial.print( intervals[ 0 ] );
			Serial.println();
		}		
	}
}