tests-mbed_drivers-lp_timer: change delay method #7471
Conversation
The test sometimes fails on NRF51_DK (test case: "Test: LowPowerTimer - time measurement 1 ms.") in morph tests. The test verifies if LowPowerTimer class correctly counts elapsed time. Sometimes we got measured ~1600 us for delay 1000 us (delta 550 us). The delay is performed using `wait_us()` function which for delays greater than or equal to 1 ms (our case) calls `Thread::wait((uint32_t)ms);`. This causes rescheduling and potentially can put board into sleep (deep sleep mode is disabled by `wait_us()`). For our test purposes we don't need rescheduling/sleep since this actions takes extra time and have influence on the time measurement accuracy. The solution is to implement function for delay which is based on busy loop and uses us ticker. It has been verified that this solves the problem. With this fix when measurement of 1 ms is repeated 1000 times we got usually measured time equal to ~1080 us, and sometimes ~1300us (checked that this is caused by systick interrupt handling). Since this is test for drivers layer and the results are acceptable I decided to not disabling systick in the test).
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👍 👍 👍 For the description and commit message! I'm good with the proposed fix and implementation. /morph build |
Build : SUCCESSBuild number : 2574 Triggering tests/morph test |
Exporter Build : SUCCESSBuild number : 2217 |
Test : FAILUREBuild number : 2327 |
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I'm confused with the result.
This PR only changes |
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/morph test |
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/morph build |
Build : SUCCESSBuild number : 2581 Triggering tests/morph test |
Exporter Build : FAILUREBuild number : 2223 |
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Exporter left too soon |
Exporter Build : SUCCESSBuild number : 2226 |
Test : SUCCESSBuild number : 2333 |
tests-mbed_drivers-lp_timer: change delay method
Description
The test sometimes fails on NRF51_DK (test case: "Test: LowPowerTimer - time measurement 1 ms.") in morph tests.
The test verifies if LowPowerTimer class correctly counts elapsed time. Sometimes we got measured ~1600us for delay 1000 us (delta 550 us).
The delay is performed using
wait_us()function which for delays greater than or equal to 1 ms (our case) callsThread::wait((uint32_t)ms);. This causes rescheduling and potentially can put board into sleep (deep sleep mode is disabled bywait_us()). For our test purposes we don't need rescheduling/sleep since this actions takes extra time and have influence on the time measurement accuracy.The solution is to implement function for delay which is based on busy loop and uses us ticker. It has been verified that this solves the problem. With this fix when test case is repeated 1000 times we got usually measured time equal to ~1080 us, and sometimes ~1300us (checked that this is caused by systick interrupt handling). Since this is test for drivers layer and the results are acceptable I decided to not disabling systick in the test).
Pull request type