We are building up an Arduino compatible with the ATMEGA328 in the TQFP package for the first time. Now we have built two two prototypes and they both seem to be experiencing the same failure. They both worked well to start with. They accepted the boot loader and could be programmed from an FTDI cable. The SD card interface even worked.
Then, after about an hour of running a version of blink (alternating two leds), one LED starts blinking rapidly. It is like it is being reset very quickly.
I can still upload programs via the ISP interface and can swap the initial LED in which case that is the LED that blinks rapidly. I can reinstall the bootloader, but no longer will it accept programs from the FTDI interface.
We have built several boards in using the DIP version of the ATMEGA328 and just copied the schematic for this design. Has anyone else experienced issued using the TQFP?
I have uploaded the schematic, and provided a link below.