From eef689b2e209dcf84c149ee4866c2a007676dc71 Mon Sep 17 00:00:00 2001 From: Akshay Nair Date: Fri, 6 Feb 2026 16:46:28 +0530 Subject: Fix timer interrupt priority + refactor --- src/rtc.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100644 src/rtc.c (limited to 'src/rtc.c') diff --git a/src/rtc.c b/src/rtc.c new file mode 100644 index 0000000..1ac50c3 --- /dev/null +++ b/src/rtc.c @@ -0,0 +1,36 @@ +#include +#include +#include +#include + +#include "rtc.h" + +void rtc_setup(void) { + // Set prescaler CS12 + CS10 (F_CPU / 1024) + CTC + // For 32768Hz -> 32768/1024 = 32Hz + TCCR1B = (1 << CS12) | (1 << CS10) | (1 << WGM12) | (1 << WGM13); + TCCR1A = (1 << WGM11) | (1 << WGM10); + + TCNT1 = 0; // Start counting from 0 + OCR1A = 31; // 0-31 = 32 counts before timer interrupt (1Hz) + OCR1B = 0; + + TIFR1 = (1 << OCF1A) | (1 << OCF1B) | (1 << TOV1); // Clear interrupt flags + TIMSK1 = (1 << OCIE1A); // Enable timer overflow interrupt +} + +volatile uint8_t seconds = 10; +volatile uint8_t minutes = 0; +volatile uint8_t hours = 0; + +void rtc_increment(void) { + uint8_t s = seconds + 1; + seconds = s % 60; + if (s >= 60) { + uint8_t m = minutes + 1; + minutes = m % 60; + if (m >= 60) { + hours = (hours + 1) % 24; + } + } +} -- cgit v1.3.1