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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 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" );
}
}
}
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