At a glance, your proposed modification looks okay. However, please keep in mind that the Pololu AVR Library was not written with the ATmega2560 in mind (it was written for our now mostly discontinued Orangutan robot controllers). So, there is no guarantee that the code will work without more significant changes, and helping to modify our library to that extent is beyond the scope of our technical support.
Based on your other thread, my impression is you might be trying to use our AVR library because it has a lot of the functionality that you are looking for (control motor drivers, control buzzer, read QTR sensors, etc.), but since it does not support the ATmega2560, I suspect it would be easier to use separate libraries (ones that are more directly intended for use with your microcontroller) for each of those tasks. For example, you might consider these libraries for the QTR sensors and buzzer:
- GitHub - pololu/qtr-sensors-arduino: Arduino library for the Pololu QTR reflectance sensors
- GitHub - pololu/pololu-buzzer-arduino: C++ library for the Arduino IDE that allows you to play notes and songs on a buzzer.
And if you post information about the specific motor drivers you are using, we might be able to offer a recommendation for code to control those.
- Patrick