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