85 lines
2.0 KiB
C
85 lines
2.0 KiB
C
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#include <stdint.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <avr/pgmspace.h>
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#include "led.h"
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#include "sleep_led.h"
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/* Software PWM
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* ______ ______ __
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* | ON |___OFF___| ON |___OFF___| ....
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* |<-------------->|<-------------->|<- ....
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* PWM period PWM period
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*
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* 256 interrupts/period[resolution]
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* 64 periods/second[frequency]
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* 256*64 interrupts/second
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* F_CPU/(256*64) clocks/interrupt
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*/
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#define SLEEP_LED_TIMER_TOP F_CPU/(256*64)
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void sleep_led_init(void)
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{
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/* Timer1 setup */
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/* CTC mode */
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TCCR1B |= _BV(WGM12);
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/* Clock selelct: clk/1 */
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TCCR1B |= _BV(CS10);
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/* Set TOP value */
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uint8_t sreg = SREG;
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cli();
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OCR1AH = (SLEEP_LED_TIMER_TOP>>8)&0xff;
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OCR1AL = SLEEP_LED_TIMER_TOP&0xff;
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SREG = sreg;
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}
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void sleep_led_enable(void)
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{
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/* Enable Compare Match Interrupt */
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TIMSK1 |= _BV(OCIE1A);
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}
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void sleep_led_disable(void)
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{
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/* Disable Compare Match Interrupt */
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TIMSK1 &= ~_BV(OCIE1A);
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}
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/* Breathing Sleep LED brighness(PWM On period) table
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* (32[steps] * 8[duration]) / 64[PWM periods/s] = 4 second breath cycle
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*/
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static const uint8_t breathing_table[32] PROGMEM = {
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0, 0, 0, 2, 9, 21, 37, 56, 78, 127, 151, 175, 197, 216, 232, 244,
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254, 244, 216, 197, 175, 151, 127, 78, 56, 37, 21, 9, 2, 0, 0, 0
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};
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ISR(TIMER1_COMPA_vect)
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{
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/* Software PWM
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* timer:1111 1111 1111 1111
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* \----/\-/ \-------/+--- count(0-255)
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* | +--------------- duration of step(8)
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* +-------------------- index of step table(0-31)
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*/
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static union {
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uint16_t row;
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struct {
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uint8_t count:8;
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uint8_t duration:3;
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uint8_t index:5;
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} pwm;
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} timer = { .row = 0 };
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timer.row++;
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// LED on
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if (timer.pwm.count == 0) {
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led_set(1<<USB_LED_CAPS_LOCK);
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}
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// LED off
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if (timer.pwm.count == pgm_read_byte(&breathing_table[timer.pwm.index])) {
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led_set(0);
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}
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}
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