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/*
* propeller-clock.pde
*
* Copyright (C) 2011 Tim Marston <edam@waxworlds.org>
*
* This file is part of propeller-clock (hereafter referred to as "this
* program"). See http://ed.am/software/arduino/propeller-clock for more
* information.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//_____________________________________________________________________________
// data
// when non-zero, the time (in microseconds) of a new fan pulse that
// has just occurred, which means that segment drawing needs to be
// restarted
static unsigned long new_pulse_at = 0;
// the time (in microseconds) when the last fan pulse occurred
static unsigned long last_pulse_at = 0;
// duration (in microseconds) that a segment should be displayed
static unsigned long segment_step = 0;
// remainder after divisor and a tally of the remainders for each segment
static unsigned long segment_step_sub_step = 0;
static unsigned long segment_step_sub = 0;
// display mode
static
//_____________________________________________________________________________
// code
// ISR to handle the pulses from the fan's tachiometer
void fanPulseHandler()
{
// the fan actually sends two pulses per revolution. These pulses
// may not be exactly evenly distributed around the rotation, so
// we can't recalculate times on every pulse. Instead, we ignore
// every other pulse so timings are based on a complete rotation.
static bool ignore = true;
ignore = !ignore;
if( !ignore )
{
// set a new pulse time
new_pulse_at = micros();
}
}
// draw a particular segment
void drawNextSegment( bool reset )
{
static unsigned int segment = 0;
if( reset ) segment = 0;
segment++;
for( int a = 0; a < 10; a++ )
digitalWrite( a + 4, ( ( segment >> a ) & 1 )? HIGH : LOW );
}
// calculate time constants when a new pulse has occurred
void calculateSegmentTimes()
{
// check for overflows, and only recalculate times if there isn't
// one (if there is, we'll just go with the last pulse's times)
if( new_pulse_at > last_pulse_at )
{
// new segment stepping times
unsigned long delta = new_pulse_at - last_pulse_at;
segment_step = delta / NUM_SEGMENTS;
segment_step_sub = 0;
segment_step_sub_step = delta % NUM_SEGMENTS;
}
// now we have dealt with this pulse, save the pulse time and
// clear new_pulse_at, ready for the next pulse
last_pulse_at = new_pulse_at;
new_pulse_at = 0;
}
// wait until it is time to draw the next segment or a new pulse has
// occurred
void waitTillNextSegment( bool reset )
{
static unsigned long end_time = 0;
// handle reset
if( reset )
end_time = last_pulse_at;
// work out the time that this segment should be displayed until
end_time += segment_step;
semgment_step_sub += semgment_step_sub_step;
if( semgment_step_sub >= NUM_SEGMENTS ) {
semgment_step_sub -= NUM_SEGMENTS;
end_time++;
}
// wait
while( micros() < end_time && !new_pulse_at );
}
// main setup
void setup()
{
// set up an interrupt handler on pin 2 to nitice fan pulses
attachInterrupt( 0, fanPulseHandler, RISING );
digitalWrite( 2, HIGH );
// set up output pins (4 to 13) for the led array
for( int a = 4; a < 14; a++ )
pinMode( a, OUTPUT );
// serial comms
Serial.begin( 9600 );
}
// main loop
void loop()
{
// if there has been a new pulse, we'll be resetting the display
bool reset = new_pulse_at? true : false;
// draw this segment
drawNextSegment( reset );
// do we need to recalculate segment times?
if( reset )
calculateSegmentTimes();
// wait till it's time to draw the next segment
waitTillNextSegment( reset );
}
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