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Timer accuracy improvement: `+=` instead of `=`.

This commit is contained in:
Andrew Makousky 2020-09-13 18:38:44 -05:00
parent c36265d2da
commit 3858671656
1 changed files with 6 additions and 4 deletions
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10
firmware/rtc/MacRTC.c
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@ -334,11 +334,13 @@ void oflowInterrupt(void)
{
numOflows++;
if (numOflows == LIM_OFLOWS) {
// Configure a timer interrupt to handle the final remainder cycle
// wait. We simply subtract the value from 256, which is the same
// as going negative two's complement and using 8-bit wrap-around.
/* Configure a timer interrupt to handle the final remainder cycle
wait. We simply subtract the value from 256, which is the same
as going negative two's complement and using 8-bit wrap-around.
Also, since the timer may have ticked a few cycles since
wrap-around, accumulate via `+=`. */
fracRemain += NUMER_FRAC_REMAIN;
TCNT0 = (fracRemain >= DENOM_FRAC_REMAIN) ?
TCNT0 += (fracRemain >= DENOM_FRAC_REMAIN) ?
-(LIM_REMAIN + 1) : -LIM_REMAIN;
fracRemain &= MASK_FRAC_REMAIN;
} else if (numOflows == LIM_OFLOWS + 1) {