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fix: suspend SysTick in LowPower_stop() - #137
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Like LowPower_sleep(), suspend the tick before entering Stop mode. With DBGMCU DBG_STOP set, the core clock and SysTick keep running in Stop mode and the pending tick interrupt wakes WFI despite PRIMASK, so deepSleep() returned almost immediately. The tick is enabled again on wake-up by SystemClock_ConfigFromStop() (HAL_RCC_ClockConfig() -> HAL_InitTick()), before the existing HAL_Delay(10). Fixes stm32duino#135 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Summary
Suspend the SysTick interrupt in
LowPower_stop(), asLowPower_sleep()already does.This PR fixes/implements the following bugs/features
LowPower.deepSleep()returns almost immediately when DBGMCUDBG_STOPis set (deepSleep() returns immediately when DBGMCU DBG_STOP is set: LowPower_stop() doesn't suspend SysTick #135)Motivation
With
DBG_STOPset, the core clock keeps running in Stop mode (on STM32L0 per RM0367, DBGMCU_CR), so SysTick keeps counting and its pending interrupt endsWFIeven with PRIMASK set.deepSleep(2000)then returns about 40 times per second.DBG_STOPsurvives every reset except power-on, so once set by debug code or a debug session, deep sleep stays broken until a power cycle. This isn't specific to STM32F1: any series whereDBG_STOPkeeps the core clock running in Stop is affected. WhenDBG_STOPis clear, suspending the tick changes nothing.No explicit
HAL_ResumeTick()is added: on wake-upSystemClock_ConfigFromStop()reconfigures the clocks throughHAL_RCC_ClockConfig(), which callsHAL_InitTick()and re-enables the SysTick interrupt before the existingHAL_Delay(10).The same change was proposed in #102 (closed unmerged by its author) for a related debug case (RTC frozen during debug).
Validation
Tested on an AcSiP S76S (STM32L073RZ, variant
ACSIP_S76S) with the repro sketch from #135:DBG_STOPsetDBG_STOPcleardeepSleep(2000)returns ~40 times/sCode formatting
Checked locally with AStyle 3.6.12 and
extras/.astylerc: no changes.Closing issues
Fixes #135
🤖 Generated with Claude Code