diff options
Diffstat (limited to 'timer.c')
| -rw-r--r-- | timer.c | 28 |
1 files changed, 17 insertions, 11 deletions
@@ -5,10 +5,22 @@ #include "timer.h" -/* useconds per clock tick */ +/* prescaler is 1024 */ +#define PRESCALER ((1 << CS12) | (1 << CS10)) + +#if F_CPU == 1000000 +/* with divider 1024 each tick is 1024us */ +#define US_PER_TICK 1024 +#define MAX_US ((uint32_t) 67107840) +#elif F_CPU == 8000000 +/* with divider 1024 each clock tick is 128us with a rounding error of 64us + * per second/4ms per minute, since it’s a 16 bit timer we support up to + * 2**16-1 ticks, which is 8388480us (8s) */ #define US_PER_TICK 128 -/* max useconds with max OCRA1 */ #define MAX_US ((uint32_t) 8388480) +#else +#error "cpu speed not supported" +#endif /* max/current timer hits */ static volatile uint8_t maxhits, hits; @@ -66,10 +78,6 @@ void timerStart (const uint32_t t, const bool once) { /* enable compare match interrupt */ TIMSK1 = (1 << OCIE1A); /* set compare value */ -#if F_CPU == 8000000 - /* with divider 1024 each clock tick is 128us with a rounding error of 64us - * per second/4ms per minute, since it’s a 16 bit timer we support up to - * 2**16-1 ticks, which is 8388480us (8s) */ if (t >= MAX_US) { maxhits = t/MAX_US+1; count = UINT16_MAX; @@ -82,11 +90,9 @@ void timerStart (const uint32_t t, const bool once) { lastcount = tdiv; OCR1A = tdiv; } -#else -#error "cpu speed not supported" -#endif - /* io clock with 1024 prescaler; ctc (part 2) */ - TCCR1B = (1 << CS12) | (1 << CS10) | (1 << WGM12); + + /* prescaler and ctc (part 2) */ + TCCR1B = PRESCALER | (1 << WGM12); } void timerStop () { |