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STM32L476 fails to wake up


We are currently experiencing a critical malfunction with the STM32L476RET6 processor. The intended functionality involves waking up the processor to read a sensor, set an RTC alarm and a GPIO interrupt  and enter Stop Mode 2. The goal is to wake up from either an RTC alarm interrupt or a GPIO interrupt. The issue manifests randomly when the processor enters Stop2 mode –sometimes it fails to wake up from an RTC alarm interrupt but only responds to a GPIO interrupt. We suspect there may be an issue with the clock crystal and its circuit. We are using the ECS-crystal, part number 327-6-16-TR(not the 327-9-16-TR of the screenshot)  , with two 6.8 pF capacitors. Also we we LSE drive is LOW. Attached are files containing basic functions related to clock configuration and RTC alarm, as well as the circuit diagram of the processor with the crystal.  We would appreciate any insights or assistance in resolving this problem.

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ST Employee

You may try LSEDRIVE_MEDIUMLOW, LSEDRIVE_MEDIUMHIGH or LSEDRIVE_HIGH to see if same issue is seen.