/elec/propeller-clock

/*

 * propeller-clock.ino

 *

 * Copyright (C) 2011 Tim Marston <tim@ed.am> and Dan Marston.

 *

 * 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/>.

 */

/******************************************************************************

Set up:

 * a PC fan is wired up to a 12V power supply

 * the fan's SENSE (tachiometer) pin connected to pin 2 on the

   arduino.

 * the pins 4 to 13 on the arduino should directly drive an LED (the

   LED on pin 4 is in the centre of the clock face and the LED on pin

   13 is at the outside.

 * if a longer hand (and a larger clock face) is desired, pin 4 can be

   used to indirectly drive (via a MOSFET) multiple LEDs which turn on

   and off in unison in the centre of the clock.

 * a button should be attached to pin 3 that grounds it when pressed.

Implementation details:

 * for a schematic, see project/propeller-clock.sch.

 * the timing of the drawing of the clock face is recalculated with

   every rotation of the propeller.

 * a PC fan actually sends 2 tachiometer pulses per revolution, so the

   software skips every other one. This means that the clock may

   appear upside-down if started with the propeller in the wrong

   position. You will need to experiment to dicsover the position that

   the propeller must be in when starting the clock.

Usage instructions:

 * pressing the button cycles between variations of the current

   display mode.

 * pressing and holding the button for a second cycles between display

   modes (e.g., analogue and digital).

 * pressing and holding the button for 5 seconds enters "time set"

   mode. In this mode, the following applies:

    - the field that is being set flashes

    - pressing the button increments the field currently being set

    - pressing and holding the button for a second cycles through the

      fields that can be set

    - press and holding the button for 5 seconds to finish

******************************************************************************/

#include <Bounce.h>

//_____________________________________________________________________________

//                                                                         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;

// flag to indicate that the drawing mode should be cycled to the next one

static bool inc_draw_mode = false;

// a bounce-managed button

static Bounce button( 3, 5 );

// the time

static int time_hours = 0;

static int time_minutes = 0;

static int time_seconds = 0;

// number of segments in a full display (rotation) is 60 (one per

// second) times the desired number of sub-divisions of a second

#define NUM_SECOND_SEGMENTS 5

#define NUM_SEGMENTS ( 60 * NUM_SECOND_SEGMENTS )

//_____________________________________________________________________________

//                                                                         code

// check for button presses

void checkButtons()

{

	// update buttons

	button.update();

	// notice button presses

	if( button.risingEdge() )

		inc_draw_mode = true;

}

// keep track of time

void trackTime()

{

	// previous time and any carried-over milliseconds

	static unsigned long last_time = millis();

	static unsigned long carry = 0;

	// how many milliseonds have elapsed since we last checked?

	unsigned long next_time = millis();

	unsigned long delta = next_time - last_time + carry;

	// update the previous time and carried-over milliseconds

	last_time = next_time;

	carry = delta % 1000;

	// add the seconds that have passed to the time

	time_seconds += delta / 1000;

	while( time_seconds >= 60 ) {

		time_seconds -= 60;

		time_minutes++;

		if( time_minutes >= 60 ) {

			time_minutes -= 60;

			time_hours++;

			if( time_hours >= 24 )

				time_hours -= 24;

		}

	}

}

// draw a segment for the test display

void drawNextSegment_test( bool reset )

{

	// keep track of segment

	static unsigned int segment = 0;

	if( reset ) segment = 0;

	segment++;

	// turn on inside and outside LEDs

	digitalWrite( 4, HIGH );

	digitalWrite( 13, HIGH );

	// display segment number in binary across in the inside LEDs,

	// with the LED on pin 12 showing the least-significant bit

	for( int a = 0; a < 8; a++ )

		digitalWrite( 12 - a, ( ( segment >> a ) & 1 )? HIGH : LOW );

}

// draw a segment for the time display

void drawNextSegment_time( bool reset )

{

	static unsigned int second = 0;

	static unsigned int segment = 0;

	// handle display reset

	if( reset ) {

		second = 0;

		segment = 0;

	}

	// what needs to be drawn?

	bool draw_tick = !segment && second % 5 == 0;

	bool draw_second = !segment && second == time_seconds;

	bool draw_minute = !segment && second == time_minutes;

	bool draw_hour = !segment && second == time_hours;

	// set the LEDs

	digitalWrite( 13, HIGH );

	digitalWrite( 12, draw_tick || draw_minute );

	for( int a = 10; a <= 11; a++ )

		digitalWrite( a, draw_minute || draw_second );

	for( int a = 4; a <= 9; a++ )

		digitalWrite( 10, draw_minute | draw_second || draw_hour );

	// inc position

	if( ++segment >= NUM_SECOND_SEGMENTS ) {

		segment = 0;

		second++;

	}

}

// draw a display segment

void drawNextSegment( bool reset )

{

	static int draw_mode = 0;

 	// handle mode switch requests

	if( reset && inc_draw_mode ) {

		inc_draw_mode = false;

		draw_mode++;

		if( draw_mode >= 2 )

			draw_mode = 0;

	}

	// draw the segment

	switch( draw_mode ) {

	case 0: drawNextSegment_test( reset ); break;

	case 1: drawNextSegment_time( reset ); break;

	}

}

// 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;

	segment_step_sub += segment_step_sub_step;

	if( segment_step_sub >= NUM_SEGMENTS ) {

		segment_step_sub -= NUM_SEGMENTS;

		end_time++;

	}

	// wait

	while( micros() < end_time && !new_pulse_at );

}

// 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();

	}

}

// 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 );

	// set up mode-switch button on pin 3

	pinMode( 3, INPUT );

	// 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;

	// only do this stuff at the start of a display cycle, to ensure

	// that no state changes mid-display

	if( reset )

	{

		// check buttons

		checkButtons();

		// keep track of time

		trackTime();

	}

	// 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 );

}