2021-08-16 12:19 PM
We are seeing an issue with the STM32L4R5ZI that does not boot 100% of the time if nRST is asserted after powering up (i.e., pressing and releasing reset button). We have seen this issue with the Nucleo board and with two different boards we made ourselves.
We have seen this behavior using code generated by CubeMX 6.2.1 using STM32Cube_FW_L4_V1.17.0
Observations
Work Arounds
Has anyone else seen this, and is it a firmware issue?
NB: I've used STM32 a lot and have not seen this issue before. Wondering if L4R5 SWD could be involved since flashing can recover it, mostly.
Robert Dowling
2021-08-16 12:37 PM
The L4+ will detect if the FLASH has a valid image, and with latch a BOOT-to-ROM mode that is only cleared with a power cycle. A blank or erased device will latch into this state.
Given the low voltages at which the core might be viable, I'd probably look to having a rather high thresholding POR circuit that holds the reset for a 100-200ms beyond that.
2021-10-03 03:08 AM