I have a customer with one of my products on his CNC machine. For whatever reason, his machine seems to have an unusually large amount of electrical noise. Three times now, this has resulted in the ProMini on my board having its FLASH at least partially erased or corrupted to the point it no longer functioned correctly. There has never been any actual damage to the chip itself, and re-FLASHing gets it going again. Ideally, we could figure out what is going on with his machine, but in reality, that is unlikely to happen. So I’m wondering if there is some way to make it more difficult for the FLASH to get corrupted, by setting a LOCK bit or something similar.
I realize this may be an exercise in futility, given that if the problem is caused purely by electrical noise, this may be purely a hardware phenomena. But, I have to at least try. So, I’m thinking I could prepare a replacement ProMini with no boot loader (eliminating the possibility that the boot loader FLASH programmer is somehow being activated), and setting any fuses, etc. that might at least make it more difficult for the FLASH to get erased or otherwise corrupted.
Any ideas? What fuse options are there that might be relevant, and how do I change them?