Posted on May 17, 2011 at 13:44Hi Thomas,
There are a couple of ways of attacking this.
On the STM32F103RET part the flash pages are 2KB. Depending on how many free pages you have you could put calibration data in it's own page, or tack it on the back-end of a page at the end of the firmware if it has space. For example if your firmware goes to 0x0801F6FF there'd be 0x100 bytes of spare space. This would assume you write in only once, and that if you upgraded the firmware you would retain a copy, or move it somewhere else.
When it comes to erasing pages, you can copy critical/old settings to RAM, and rewrite them after the erase. Here you would want to be cautious about the window of vulnerability for the power to fail, or the erase/write to fail.
Another way would be to ping-and-pong between two flash pages, with a sequence number that would permit you locate the most recent setting, but also have the old ones to revert too. To update you would erase the oldest settings, and write the new ones there.
If your settings only take say 256 bytes, you could write up to 8 copies in a 2K page, again either with a sequence number, or checking for a 0xFFFF marker. At startup you could enumerate through the copies to find the most recent.
-Clive
