tmk_core/common/avr/sleep_led.c

   1 #include <stdint.h>
   2 #include <avr/io.h>
   3 #include <avr/interrupt.h>
   4 #include <avr/pgmspace.h>
   5 #include "led.h"
   6 #include "sleep_led.h"
   7
   8 /* Software PWM
   9  *  ______           ______           __
  10  * |  ON  |___OFF___|  ON  |___OFF___|   ....
  11  * |<-------------->|<-------------->|<- ....
  12  *     PWM period       PWM period
  13  *
  14  * 256              interrupts/period[resolution]
  15  * 64               periods/second[frequency]
  16  * 256*64           interrupts/second
  17  * F_CPU/(256*64)   clocks/interrupt
  18  */
  19 #define SLEEP_LED_TIMER_TOP F_CPU/(256*64)
  20
  21 void sleep_led_init(void)
  22 {
  23     /* Timer1 setup */
  24     /* CTC mode */
  25     TCCR1B |= _BV(WGM12);
  26     /* Clock selelct: clk/1 */
  27     TCCR1B |= _BV(CS10);
  28     /* Set TOP value */
  29     uint8_t sreg = SREG;
  30     cli();
  31     OCR1AH = (SLEEP_LED_TIMER_TOP>>8)&0xff;
  32     OCR1AL = SLEEP_LED_TIMER_TOP&0xff;
  33     SREG = sreg;
  34 }
  35
  36 void sleep_led_enable(void)
  37 {
  38     /* Enable Compare Match Interrupt */
  39     TIMSK1 |= _BV(OCIE1A);
  40 }
  41
  42 void sleep_led_disable(void)
  43 {
  44     /* Disable Compare Match Interrupt */
  45     TIMSK1 &= ~_BV(OCIE1A);
  46 }
  47
  48 void sleep_led_toggle(void)
  49 {
  50     /* Disable Compare Match Interrupt */
  51     TIMSK1 ^= _BV(OCIE1A);
  52 }
  53
  54
  55 /* Breathing Sleep LED brighness(PWM On period) table
  56  * (64[steps] * 4[duration]) / 64[PWM periods/s] = 4 second breath cycle
  57  *
  58  * http://www.wolframalpha.com/input/?i=%28sin%28+x%2F64*pi%29**8+*+255%2C+x%3D0+to+63
  59  * (0..63).each {|x| p ((sin(x/64.0*PI)**8)*255).to_i }
  60  */
  61 static const uint8_t breathing_table[64] PROGMEM = {
  62 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 6, 10,
  63 15, 23, 32, 44, 58, 74, 93, 113, 135, 157, 179, 199, 218, 233, 245, 252,
  64 255, 252, 245, 233, 218, 199, 179, 157, 135, 113, 93, 74, 58, 44, 32, 23,
  65 15, 10, 6, 4, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
  66 };
  67
  68 ISR(TIMER1_COMPA_vect)
  69 {
  70     /* Software PWM
  71      * timer:1111 1111 1111 1111
  72      *       \_____/\/ \_______/____  count(0-255)
  73      *          \    \______________  duration of step(4)
  74      *           \__________________  index of step table(0-63)
  75      */
  76     static union {
  77         uint16_t row;
  78         struct {
  79             uint8_t count:8;
  80             uint8_t duration:2;
  81             uint8_t index:6;
  82         } pwm;
  83     } timer = { .row = 0 };
  84
  85     timer.row++;
  86
  87     // LED on
  88     if (timer.pwm.count == 0) {
  89         led_set(1<<USB_LED_CAPS_LOCK);
  90     }
  91     // LED off
  92     if (timer.pwm.count == pgm_read_byte(&breathing_table[timer.pwm.index])) {
  93         led_set(0);
  94     }
  95 }