How to use the untraced pins for ATmega2560?

Hello. On the original Arduino from ATmega2560 chip not all port pins are traced (for me interested this ports: 29, 47-48 - they are comfortable to trace on my board). Is it possible (and how) to use them in the Arduino IDE? |420x500

Yes, it is possible to use any pin in the Arduino IDE. This is a matter of SW. If the pin is not configured in the Arduino SW, you can modify the pins_arduino.h for the mega variant and add it to the configuration. For the AVR tools you need not to do anything. The second thing is the HW modification. It is a problem. A long time ago, I made modification on my Mega 2560 R3 board due to pin 29 (TOSC1) usage. I connected Atmega's pin 29 to the N.C. pin on Arduino's power header by a wire. Header pin is marked for 'future use'. It should work for you also but what about the rest 2 pins. You have to solve the HW to add the connector or what. It is on your imagination.