Hi,
I have an unassembled pro mini 3.3V 8mhz board. I've assembled an atmega328P, the .1uF capacitors, a murata 8mhz capless resonator, the led + resistor on pin 13 and a 10K resistor on reset. The regulator is not connected - supplying regulated 5V or 3.3V directly to the VCC pin.
I've burnt the Pro Mini 3.3V 8mhz with 328P bootloader.
I can program the board (using an Uno board without a atmega chip using rx,tx lines) if I connect 5V from the UNO to VCC on the pro mini, but it won't upload when I connect 3.3V.
I programmed the Blink program @ 5V (works) and then changed to 3.3V after the download. The led doesn't light up @ 3.3V. Also tried programming the chip to use internal oscillator - same results - only blinks when 5V is connected to VCC.
Thank you.
Check the BODLEVEL fuses!
Thanks MadWorm! Tried that - disabled BODLEVEl fuses (fuses set at : FF DA FF ) - getting same results.