Hello,
I need to design a system that needs to run for several years non stop. It is critical that it wakes up about once a minute (exact time is irrelevant, just the interval in itself needs to be constant) for this entire period.
So I have two problems I that I still need to think about.
First are the firmware updates. It is ok to update the firmware in between the intervals. The current data is stored in external FRam so the processor can be reset and return to the last state. It just may not interrupt the task it does every minute. Any tips on how to do this "the good way"? I thought of putting the firmware in an external flash first an then have the MSP update itself when the task is done. Or using a custom serial bootloader that simply only answers when it has just finished the task, thus giving about a minute to update. The timeinterval is given by an external little timer that already puts out a ~1 minute pulse, so it will not fall out of sync after updating.
The second issue is the power. I have planed a BQ2407x that would usually run from a USB mains adapter and functions as UPS with a Li Lion battery. But I need to have a sort of emergency backup CR2032 on the same PCB that would come into action if all other sources from the BQ fail. How could I do this? The application is very low power (idle 15µA, active 20mA for a very short time), so a CR2032 should last for enough time to get the main supply running again. Any tips or devices that can do that?
Thank you
Kind regards
