The version I installed uses M functions. I use Miniterm in linux and issue test commands to heater. "M104 S100" sets temperature. "M105" reads back the temperature.
I am using a stepper motor driven as A axis from EMC. I assume you are using a DC motor. The old commands for motor were "M101" to start extruder and "M103" to stop extruder. Note that some versions of the firmware need the speed set before the M101 is activated. ie "M108 S100". Note also the space between the M word and the S word is required. Also a carriage return after the command. That is why you cannot use terminal in the Arduino IDE to issue test commands.
This is all very firmware dependant. I am using generation 2 electronics with an Arduino and the standard release firmware to drive the heater only.