Arduino due waveform generator

My assignment to implement codes for a function generator just as in (only square wave);

https://www.arduino.cc/en/Tutorial/DueSimpleWaveformGenerator  

its frequency must be between 1Hz and 10Khz (and how it is controlled must be explained)

no need for buttons or potentiometer as in the example, because we will control the frequency by sending data via bluetooth.

to sum up, create a function generator (square wave)  such that, we will control 3 variable, its amplitude, duty cycle and frequency (1 Hz to 10 Khz). by simply changing these variables (in the code), we will change functions frequnecy, amplitude and duty cycle.