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test/xtimer_drift: interval calculation #9625

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Merged
A-Paul merged 1 commit into from
Sep 6, 2018
Merged

test/xtimer_drift: interval calculation #9625

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12 changes: 8 additions & 4 deletions tests/xtimer_drift/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,10 @@ void *worker_thread(void *arg)
{
(void) arg;

/* Calculate interval based on possible precision when 'XTIMER_SHIFT > 0',
* to apply precision loss to expected interval length.
* test_interval != TEST_INTERVAL */
uint32_t test_interval = xtimer_usec_from_ticks(xtimer_ticks_from_usec(TEST_INTERVAL));
uint32_t loop_counter = 0;
uint32_t start = 0;
uint32_t last = 0;
Expand All @@ -111,14 +115,14 @@ void *worker_thread(void *arg)
else if ((loop_counter % TEST_HZ) == 0) {
uint32_t us = now % US_PER_SEC;
uint32_t sec = now / US_PER_SEC;
uint32_t expected = start + loop_counter * TEST_INTERVAL;
uint32_t expected = start + loop_counter * test_interval;
int32_t drift = now - expected;
expected = last + TEST_HZ * TEST_INTERVAL;
expected = last + TEST_HZ * test_interval;
int32_t jitter = now - expected;
printf("now=%" PRIu32 ".%06" PRIu32 " (0x%08" PRIx32 " ticks), ",
sec, us, ticks.ticks32);
sec, us, ticks.ticks32);
printf("drift=%" PRId32 " us, jitter=%" PRId32 " us\n",
drift, jitter);
drift, jitter);
last = now;
}
++loop_counter;
Expand Down