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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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/******************************************************************************
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* a PC fan is wired up to a 12V power supply
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* the fan's SENSE (tachiometer) pin connected to pin 2 on the
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* the pins 4 to 13 on the arduino should directly drive an LED (the
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LED on pin 4 is in the centre of the clock face and the LED on pin
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* if a longer hand (and a larger clock face) is desired, pin 4 can be
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used to indirectly drive a transistor which in turn drives several
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LEDs that turn on anf off in unison in the centre of the clock.
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* a button should be attached to pin 3 that grounds it when pressed.
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* A DS1307 remote clock is connected via I2C on analog pins 4 and 5.
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Implementation details:
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* for a schematic, see ../project/propeller-clock.sch.
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* the timing of the drawing of the clock face is recalculated with
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every rotation of the propeller.
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* a PC fan actually sends 2 tachiometer pulses per revolution, so the
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software skips every other one. This means that the clock may
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appear upside-down if started with the propeller in the wrong
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position. You will need to experiment to dicsover the position that
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the propeller must be in when starting the clock.
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* pressing the button cycles between variations of the current
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* pressing and holding the button for a second cycles between display
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modes (e.g., analogue and digital).
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* pressing and holding the button for 5 seconds enters "time set"
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mode. In this mode, the following applies:
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- the field that is being set flashes
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- pressing the button increments the field currently being set
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- pressing and holding the button for a second cycles through the
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fields that can be set
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- pressing and holding the button for 5 seconds sets the time and
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******************************************************************************/
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//_____________________________________________________________________________
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static unsigned long segment_step_sub_step = 0;
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static unsigned long segment_step_sub = 0;
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// flag to indicate that the drawing mode should be cycled to the next one
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static bool inc_draw_mode = false;
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// a bounce-managed button
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static Bounce button( 3, 50 );
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static int time_hours = 0;
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static int time_minutes = 0;
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static int time_seconds = 0;
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// number of segments in a full display (rotation) is 60 (one per
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// second) times the desired number of sub-divisions of a second
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#define NUM_SECOND_SEGMENTS 5
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#define NUM_SEGMENTS ( 60 * NUM_SECOND_SEGMENTS )
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//_____________________________________________________________________________
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// check for button presses
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// notice button presses
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if( button.risingEdge() )
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inc_draw_mode = true;
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// keep track of time
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// previous time and any carried-over milliseconds
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static unsigned long last_time = millis();
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static unsigned long carry = 0;
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// how many milliseonds have elapsed since we last checked?
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unsigned long next_time = millis();
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unsigned long delta = next_time - last_time + carry;
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// update the previous time and carried-over milliseconds
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last_time = next_time;
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carry = delta % 1000;
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// add the seconds that have passed to the time
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time_seconds += delta / 1000;
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while( time_seconds >= 60 ) {
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if( time_minutes >= 60 ) {
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if( time_hours >= 24 )
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// ISR to handle the pulses from the fan's tachiometer
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void fanPulseHandler()
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// the fan actually sends two pulses per revolution. These pulses
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// may not be exactly evenly distributed around the rotation, so
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// we can't recalculate times on every pulse. Instead, we ignore
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// every other pulse so timings are based on a complete rotation.
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static bool ignore = true;
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// set a new pulse time
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new_pulse_at = micros();
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// turn an led on/off
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void ledOn( int num, bool on )
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if( num < 0 || num > 9 ) return;
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// convert to pin no.
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// pin 4 needs to be inverted (it's driving a PNP)
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if( num == 4 ) on = !on;
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digitalWrite( num, on? HIGH : LOW );
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// draw a segment for the test display
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void drawNextSegment_test( bool reset )
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// keep track of segment
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// draw a particular segment
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void drawNextSegment( bool reset )
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static unsigned int segment = 0;
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if( reset ) segment = 0;
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// turn on inside and outside LEDs
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// display segment number in binary across in the inside LEDs,
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// with the LED on pin 12 showing the least-significant bit
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for( int a = 0; a < 8; a++ )
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ledOn( 8 - a, ( segment >> a ) & 1 );
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// draw a segment for the time display
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void drawNextSegment_time( bool reset )
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static int second = 0;
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static int segment = 0;
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// handle display reset
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// what needs to be drawn?
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bool draw_tick = !segment && second % 5 == 0;
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bool draw_second = !segment && second == time_seconds;
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bool draw_minute = !segment && second == time_minutes;
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bool draw_hour = !segment && second == time_hours;
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ledOn( 8, draw_tick || draw_minute );
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for( int a = 6; a <= 7; a++ )
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ledOn( a, draw_minute || draw_second );
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for( int a = 0; a <= 5; a++ )
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ledOn( a, draw_minute || draw_second || draw_hour );
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if( ++segment >= NUM_SECOND_SEGMENTS ) {
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// draw a display segment
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void drawNextSegment( bool reset )
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static int draw_mode = 0;
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// handle mode switch requests
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if( reset && inc_draw_mode ) {
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inc_draw_mode = false;
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switch( draw_mode ) {
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case 0: drawNextSegment_test( reset ); break;
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case 1: drawNextSegment_time( reset ); break;
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for( int a = 0; a < 10; a++ )
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digitalWrite( a + 4, ( ( segment >> a ) & 1 )? HIGH : LOW );