I have two of these nice dev boards, which I’ve been using for a while at 5V with no problems at all. I am working with a few 3.3V parts that use I2C or SPI, and rather than use level shifters I thought I’d just run the ATmega168 at 3.3V and 8 MHz.
I’m using an Atmel Dragon for programming, and it works perfectly with the P28 running at 5V and 8 MHz, but at 3.3V neither fuses or flash verifies. The Dragon correctly senses the target voltage. OK, so I programmed the 168 at 5V, then tried to run it at 3.3 V. Doesn’t work. Even a program that flashes the LED at 5V doesn’t do anything at 3.3V.
The ATmega datasheet says the 168 will run at up to 10 MHz on as low as 2.7V, and I have verified the uC is getting 3.3V.
Does anyone have any ideas how to diagnose what’s happening?
Thanks,
D.