Hi everyone,
I have some issue when my device is in very low temperature of -60°C / -70°C.
We use an NRF52832 (SDK 15) on modules (BMD-300 frome UBLOX formely RIGADO).
Our use case it makes connected autonomous sensor temperature (with batterie) with a cellular gateway and app, this solution work perfectly on normal condition.
We tested some case on a sample of 120 devices :
- At -55°C all device test works correctly
- At -60°C some device (2-3%) makes weird compartments :
- Advertising name change (normally it's K-TAG and sometimes we have D-TAG, sometimes it's blank, etc.)
- Caracterisitque disappear or change of number
- Error on temperature
- At -65°C same symptoms but for 20% of the tested device
- At -70°C about 50% have the problem
When we come back at normal temperature some device rework perfectly and some device needs to be manually reset. (We have implemented watchdog function.)
The sensors are powered by batterie to eliminate the batterie problem we have tested with a laboratory alimentation (on ambiant temps, juste wire at -70°C) and we see an over consumption (about 100µA instead of 12 µA) and a lot of reset.
So we try with debuggers and J-LINK RTT Viewer and when the J-LINK was connected we don't see any problem.
We think the problem is the RAM retention could be don't work perfectly at low temp and we will test our application without sleeping time but maybe some guys have some tips for us ?
And I would know how the RAM retention works, it's a timer refresh the RAM every each period ? If yes timer takes his period from the LF Quartz, or an internal RC, or some other method ?
Thanks for your help,
Best regards,
Romain P.
