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Viewing changes to test/receiver/pulse-width/main.ino

  • Committer: Tim Marston
  • Date: 2013-10-23 19:58:45 UTC
  • Revision ID: tim@ed.am-20131023195845-6coin3ndwkkc52np
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test/receiver/pulse-width/main.ino
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// microseconds.  It takes several measurements and prints it the average over
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// serial.
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//
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// NOTES: Due to the way our receiver works (by varying the position of the
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// rising edge of the pulse and keeping the falling edge fixed), it is
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// sufficient for us to measure the pule width to determine the channel value
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// (e.g., throttle position).  But it should be noted that this relies on a
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// quirk of our receiver/transmitter and it is not truly measuring PPM.  Our
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// next experiment is measuring PPM (../ppm-read).
 
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// number of signal pulses to average
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#define AVERAGE_SAMPLES 1
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// should average be result, or damping?
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#define AVERAGE_DAMP 1
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// graphic display
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#define GRAPH 1
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#define GRAPH_MIN 1000
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#define GRAPH_MAX 2000
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#define GRAPH_SIZE 30
 
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#define SIGNAL_SAMPLES 10
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// set to the time that the last signal pulse was at
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        Serial.begin( 9600 );
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}
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void loop()
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{
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        unsigned long last_pulse_off = 0;
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        unsigned long intervals[ AVERAGE_SAMPLES ];     
 
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        unsigned long last_pulse = 0;
 
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        unsigned long intervals[ SIGNAL_SAMPLES ] = {0};
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        int interval_idx = 0;
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        // reset intervals
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        for( int a = 0; a < AVERAGE_SAMPLES; a++ )
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                intervals[ a ] = 0;
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#ifdef GRAPH
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        // init graph
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        char graph[ GRAPH_SIZE + 3 ];
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        for( int a = 1; a < GRAPH_SIZE + 1; a++ )
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                graph[ a ] = '-';
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        graph[ 0 ] = '[';
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        graph[ GRAPH_SIZE + 1 ] = ']';
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        graph[ GRAPH_SIZE + 2 ] = 0;
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#endif // GRAPH
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        while( true )
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        {
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                // detect pulse falling-edge
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                unsigned long pulse_on = _new_pulse_on;
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                unsigned long pulse_off = _new_pulse_off;
 
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                unsigned long new_pulse_on = _new_pulse_on;
 
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                unsigned long new_pulse_off = _new_pulse_off;
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                bool got_pulse = false;
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                if( pulse_off > last_pulse_off )
 
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                if( new_pulse_off > last_pulse )
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                {
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                        // sanity check
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                        unsigned long interval = pulse_off - pulse_on;
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                        if( interval > 800 && interval < 3000 )
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                        {
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                                // update interval buffer
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                                intervals[ interval_idx ] = pulse_off - pulse_on;
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                                if( ++interval_idx >= AVERAGE_SAMPLES )
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                                        interval_idx = 0;
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                                got_pulse = true;
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                        }
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                        last_pulse_off = pulse_off;
 
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                        // update interval buffer
 
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                        intervals[ interval_idx ] = new_pulse_off - new_pulse_on;
 
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                        if( ++interval_idx >= SIGNAL_SAMPLES )
 
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                                interval_idx = 0;
 
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                        last_pulse = new_pulse_off;
 
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                        got_pulse = true;
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                }
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                // display average?
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                if( got_pulse &&
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                        ( AVERAGE_DAMP || interval_idx == 0 ) )
 
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                if( interval_idx == 0 && got_pulse )
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                {
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                        // calculate average
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                        unsigned long ave = 0;
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                        for( int a = 0; a < AVERAGE_SAMPLES; a++ )
 
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                        double ave = 0;
 
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                        for( int a = 0; a < SIGNAL_SAMPLES; a++ )
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                                ave += intervals[ a ];
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                        ave /= AVERAGE_SAMPLES;
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#ifdef GRAPH
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                        // draw graph
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                        int pos = ( GRAPH_SIZE ) *
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                                ( ave - GRAPH_MIN ) / ( GRAPH_MAX - GRAPH_MIN );
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                        graph[ pos + 1 ] = '|';
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                        Serial.println( graph );
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                        graph[ pos + 1 ] = '-';
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#else // GRAPH
 
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                        ave /= SIGNAL_SAMPLES;
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                        // tell it like it is
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                        Serial.println( ave );
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#endif // GRAPH
 
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                        Serial.println( round( ave ) );
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                }               
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        }
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}