initial commit

1 files changed, 31 insertions, 0 deletions

diff --git a/kernel/time/mcu/atmega2560/timer.c b/kernel/time/mcu/atmega2560/timer.c
new file mode 100644
index 0000000..663df02
--- /dev/null
+++ b/kernel/time/mcu/atmega2560/timer.c
@@ -0,0 +1,31 @@
+#include <avr/interrupt.h>
+#include "sched/sched.h"
+#include "time/timer.h"
+
+void timer_init() {
+  cli();
+  TCCR3A = 0;
+  TCCR3B = 0;
+  TCCR3C = 0;
+
+  TCCR3B = (1 << WGM32); // turn on CTC mode:
+  TCCR3B |= (1 << CS32) | (0 << CS31) | (1 << CS30); // set to 1024 prescaler
+  OCR3A = 770;
+  sei();
+}
+
+void timer_start() {
+  TIMSK3 |= (1 << OCIE3A);
+}
+
+void timer_stop() {
+  TIMSK3 &= ~(1 << OCIE3A);
+}
+
+ISR(TIMER3_COMPA_vect, ISR_NAKED) {
+  SAVE_CONTEXT(); 
+  sched_tick();
+  sei();
+  RESTORE_CONTEXT();
+  asm volatile ("reti");
+}