[Time] delayMicroseconds() accuracy + Fix ticks per ms value used to compute micros #620
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ABOSTM
suggested changes
Aug 30, 2019
The timer interrupt or COUNTFLAG bit (in the SysTick Control and Status register) is activated on the transition from 1 to 0, therefore it activates every n+1 clock ticks. So, ticks per ms is SysTick->LOAD +1. Signed-off-by: Frederic Pillon <[email protected]>
delayMicroseconds() should not rely to getCurrentMicros() and should only compute required ticks for the delay requested. This allow to use it even if interrupts are disabled. Example for OneWire library. Fixes stm32duino#412 Signed-off-by: Frederic Pillon <[email protected]>
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This PR mainly fixes issue with
delayMicroseconds()on Cortex-M0 as for other series it usesDWT->CYCCNTwhich is more accurate.Then OneWire is now functional on all series.
GPIO toggling at 5µs on a NUCLEO-L053R8:
With old implementation:
With new implementation:
Fixes #412