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tests/xtimer_drift: Add explanation for drift and jitter

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This commit is contained in:
Joakim Nohlgård 2016-03-17 21:41:44 +01:00
parent 68a91426fb
commit f03194f84e
1 changed files with 4 additions and 1 deletions
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5
tests/xtimer_drift/main.c
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@ -115,7 +115,7 @@ void *worker_thread(void *arg)
int32_t drift = now - expected;
expected = last + TEST_HZ * TEST_INTERVAL;
int32_t jitter = now - expected;
printf("now=%" PRIu32 ".%06" PRIu32 " (%u hours %u min), drift=%" PRId32 ", jitter=%" PRId32 "\n",
printf("now=%" PRIu32 ".%06" PRIu32 " (%u hours %u min), drift=%" PRId32 " us, jitter=%" PRId32 " us\n",
sec, us, hr, min, drift, jitter);
last = now;
}
@ -136,6 +136,9 @@ int main(void)
(unsigned long)TEST_INTERVAL, (unsigned long)TEST_HZ);
puts("The current time will be printed once per second, along with the "
"difference between the actual and expected xtimer_now value.");
puts("The first output variable, 'drift', represents the total offset since "
"start between xtimer_now and the expected time.");
puts("The second output variable, 'jitter', represents the difference in drift from the last printout.");
puts("Two other threads are also running only to cause extra interrupts and context switches.");
puts(" <====== PC clock if running in pyterm.");
puts("");