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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
#define AVERAGE_SAMPLES 1
// should average be result, or damping?
#define AVERAGE_DAMP 1
// graphic display
#define GRAPH 0
#define GRAPH_MIN 1000
#define GRAPH_MAX 2000
#define GRAPH_SIZE 30
// 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[ AVERAGE_SAMPLES ];
int interval_idx = 0;
// reset intervals
for( int a = 0; a < AVERAGE_SAMPLES; a++ )
intervals[ a ] = 0;
#if GRAPH
// init graph
char graph[ GRAPH_SIZE + 3 ];
for( int a = 1; a < GRAPH_SIZE + 1; a++ )
graph[ a ] = '-';
graph[ 0 ] = '[';
graph[ GRAPH_SIZE + 1 ] = ']';
graph[ GRAPH_SIZE + 2 ] = 0;
#endif // GRAPH
while( true )
{
// detect pulse falling-edge
noInterrupts();
unsigned long pulse_on = _new_pulse_on;
unsigned long pulse_off = _new_pulse_off;
interrupts();
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 >= AVERAGE_SAMPLES )
interval_idx = 0;
got_pulse = true;
}
last_pulse_off = pulse_off;
}
// display average?
if( got_pulse &&
( AVERAGE_DAMP || interval_idx == 0 ) )
{
// calculate average
unsigned long ave = 0;
for( int a = 0; a < AVERAGE_SAMPLES; a++ )
ave += intervals[ a ];
ave /= AVERAGE_SAMPLES;
#if GRAPH
// draw graph
int pos = ( GRAPH_SIZE ) *
( ave - GRAPH_MIN ) / ( GRAPH_MAX - GRAPH_MIN );
graph[ pos + 1 ] = '|';
Serial.println( graph );
graph[ pos + 1 ] = '-';
#else // GRAPH
// tell it like it is
Serial.println( ave );
#endif // GRAPH
}
}
}
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