[rtl872x] Poll micros instead of rom DelayUs function. Tweak 1ms test

[scott-brust]

Problem

DELAY_01_delay_1ms_is_within_tolerance fails occasionally on p2 no_fixture tests, ie the 1ms delay ends up being out of the 6% margin of error ( > 1060 us).

Solution

Changing the HAL_Delay_Microseconds() implementation to a simple poll of HAL_Timer_Get_Micro_Seconds() seems to be no worse than using the rom DelayUs() function.
Also tweaked the system_delay_pump() logic when doing a 1ms delay, which is what happens in the DELAY_01 test.

However, the 6% threshold is still too short in some situations. Doubling it seems to ensure tests pass a higher % of the time. I still see an occasional failure where the delay took >1120 us, but this happened once in 300 test iterations. Not sure if this is infrequent enough to ignore or if the threshold should be raised even higher.

Steps to Test

Run wiring/no_fixture tests

Example App

wiring/no_fixture

References

Links to the Community, Docs, Other Issues, etc..

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)