This should not happen if we were using the chips built in brown out detection, but it seems we are not. Here is how my devkit is fused:
avrdude: safemode: Fuses OK (H:CE, E:D8, L:FF)
Rather than the default of 2.6v BOD, we are running with brown out disabled. @bateske was this a conscious choice or just how the chips came to you? We should probably fuse the production units to BOD at 3.4 or 3.5v (BODLEVEL 2…0 of 010 for 3.4v and 001 for 3.5v). Though I was just told BOD can hurt power consumption, so often that’s why places have an external power circuit that just cuts the power if it drops too lower (to protect the LIPO for one), rather than the chip doing it. Though we could also build support into the core lib.
While it might look cool it is dangerous for the device to run at super low voltage… it can result in corrupting the flash or corrupting your EEPROM.
Anyone want to volunteer to run down your devices while keeping an eye on them and reporting the voltage they finally go haywire?