root / toolbox / led.c @ 1b054655
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| 1 | dc472500 | Tom Mullins | #include "led.h" |
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| 2 | #include <avr/io.h> |
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| 3 | 1b054655 | Tom Mullins | #include <avr/interrupt.h> |
| 4 | dc472500 | Tom Mullins | |
| 5 | #define PRESCALE 64 |
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| 6 | #define CLOCK_SEL 3 |
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| 7 | |||
| 8 | /* F_CPU / PRESCALE = OCR * 1000 + ERROR */
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| 9 | #define OCR (F_CPU / PRESCALE / 1000UL) |
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| 10 | #define ERROR (F_CPU / PRESCALE - OCR * 1000UL) |
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| 11 | |||
| 12 | char count;
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| 13 | uint16_t period; |
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| 14 | |||
| 15 | uint16_t ms; |
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| 16 | uint16_t error; |
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| 17 | |||
| 18 | static void blink() { |
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| 19 | count--; |
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| 20 | if (count % 2) { |
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| 21 | led_yellow(); |
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| 22 | } else {
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| 23 | led_off(); |
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| 24 | } |
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| 25 | } |
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| 26 | |||
| 27 | ISR(TIMER0_COMPA_vect) {
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| 28 | error += ERROR; |
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| 29 | if (error >= 1000) { |
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| 30 | error -= 1000;
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| 31 | } else {
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| 32 | ms++; |
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| 33 | if (ms == period) {
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| 34 | blink(); |
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| 35 | 1b054655 | Tom Mullins | if (count == 0) { |
| 36 | dc472500 | Tom Mullins | TCCR0B = 0;
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| 37 | } |
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| 38 | ms = 0;
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| 39 | } |
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| 40 | } |
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| 41 | } |
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| 42 | |||
| 43 | void led_blink_start(unsigned int period_ms, char n_times) { |
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| 44 | led_yellow(); |
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| 45 | ms = 0;
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| 46 | error = 0;
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| 47 | count = n_times*2-1; |
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| 48 | 1b054655 | Tom Mullins | period = period_ms/2;
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| 49 | dc472500 | Tom Mullins | OCR0A = OCR; |
| 50 | 1b054655 | Tom Mullins | TIMSK = _BV(OCIE0A); |
| 51 | dc472500 | Tom Mullins | TCCR0A = _BV(WGM01); |
| 52 | TCCR0B = CLOCK_SEL; |
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| 53 | } |
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| 54 | |||
| 55 | char led_blink_done() {
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| 56 | return count == 0; |
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| 57 | } |