2023-01-20 02:34 PM
I have an ESC ECS-.327-CDX-1082 32.768KHz crystal on the LSE of an STM32F427.
I have read and followed AN2867.
All of the boards produced so far have had the oscillator come up initially.
All of the boards subjected to thermal cycling (-20°C to +70°C) have failed. (two)
In each case, the voltage on the pins (GPIO PC14 & PC15) measures 0 volts.
I expect somewhere about 0.3V.
I just replaced the MCU on one of the boards and now the oscillator works again.
Any thoughts?
2023-02-22 08:19 AM
The solution is to do a backup domain reset. There appears to be a finite amount of time between the backup domain reset and the re-enabling of the LSE oscillator. We can now sucessfully recover from this event. Thanks to all of you who have contributed.
2023-02-22 08:25 AM
Also, the voltage provided by the supercap never dropped below 2.1 volts.
2023-02-22 08:30 AM
Thanks for coming back with the solution.
> There appears to be a finite amount of time between the backup domain reset and the re-enabling of the LSE oscillator.
Can you please be a little bit more specific, i.e. how much?
Thanks,
JW
PS. Please select your post as Best so that the thread is marked as solved.
2023-04-13 06:14 AM
Sorry for the delay.
It looks as if it takes 2-10msec after the backup domain reset before the LSE is stable.
2023-04-13 07:48 AM - edited 2023-11-20 07:18 AM
LSE startup can be long... (from F407 data.)