Assuming DFR_Key keypad;
Initializes default refreshRate, keyPin, threshold, time, and key inputs.
Sets the key sample rate at once every 'r' milliseconds.
Default: 10ms
Returns an integer value based on what key is currently pressed. Return values are as follows:
Sets the analogue read value for 'btn' [getKey() code] to 'arv'.
Sets the ARV threshold value to +/- 'thr'.