I'm a complete newbie to robotics, but Nybble was to be my introduction. I've assembled Nybble but I can't get Arduino IDE to recognize the 20Mhz processor. It recognizes the other Arduino Pro or Pro mini processors in the avr/bootloaders/atmega folder but not the ATmega328_20MHz.hex file for Nybble. I've confirmed that the boards.txt file in the avr folder is the one being used, but I can' figure out why the 20MHz processor isn't being recognized by Arduino. Any suggestion?