On Wed, Apr 29, 2009 at 9:33 AM, Vincent Trouilliez <[email protected]> wrote: > Another, more likely source of problems that could cause the > hardware (CPU or whatever peripheral on the chip) is interferences from > the environment. Like electronics used in satellites, which are > sensitive to the sun's activity. When the sun sends a burst of > radiation, the satellites must be tilted/turned around, to protect the > electronics.
And it doesn't have to be quite so harsh as space, either. I can think of a project where code redesign was done to work around faults related to environmental effects. We had a product that would experience random reboots in the field. Turned out it was the watchdog randomly expiring. We spent months trying to capture the cause of these events, certain it was a software fault of some sort. We finally nailed it down to an alpha hit corrupting the memory in the processor we were using. The corrupted memory caused the processor to occasionally "get lost" and fail to tickle the watchdog, causing the hardware reset. In the end, we had to move all the code out of the internal processor memory and use external memory that was more robust with a lower FIT rate. I'm not sure what the AVR FIT rates are for their internal RAM. I did a quick perusal of their quality website (http://atmel.com/quality/quality_reliability.asp), but it's not clear to me whether the memory numbers are for flash only, or also RAM. But if they include RAM, their FIT rates are excellent. Before this, I thought watchdogs were overkill. Perhaps in consumer applications it might be, but certainly in industrial, scientific, or military applications I think a watchdog is invaluable. Far better for a critical device to reboot to a known state than to get lost and act erratically. Pete -- -- "To love for the sake of being loved is human; to love for the sake of loving is Angelic." -- Alphonse de Lamartine _______________________________________________ AVR-chat mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/avr-chat
