/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 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();

		}		

	}

}