1 files changed, 84 insertions, 0 deletions

diff --git a/common/sleep_led.c b/common/sleep_led.c
new file mode 100644
index 000000000..edf68c352
--- /dev/null
+++ b/common/sleep_led.c
@@ -0,0 +1,84 @@
+#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);
+    }
+}