this program will flash the pins on registers B, C, and D.
make a circuit with LEDs and resistors attached to all the register pins on an atmega328p.
it looks like this:
i used a usbtinyisp from adafruit with avrdude to program my chip but you can use whatever pleases you. change the makefile accordingly, i borrowed it from https://github.com/hexagon5un/AVR-Programming