I ordered a custom PCB and reflow soldered an Atmega328p-mmh to it. It is a 28 pin QFN (MLF) package and the board uses 3.3v logic. I burned the Arduino pro mini 3.3v 8MHz bootloader using Arduino as ISP successfully and was able to upload sketches and send and receive serial data no problem.
The pro mini also uses Atmega328p but its a 32 pin unit.
BUT... There is always a but.
None of my I/O seems to work.
Digital pins and I2C bus... nothing in or out.
I am wondering if I uploaded the wrong bootloader? I thought the dies were the same just a different package and pinout. Is there a difference in bootloaders between 32 and 28 pin chips? Do I need to modify something in the bootloader? How would I go about doing that? Alternative boot loader options?
I can upload sketches, why are the not working?