Code Setup

The coding is rather simple.
There are 6 input pins we are using, one for each button on the terminal, including the receiver switch which hangs up the phone.
We create variables that are detecting the voltage on the 6 inputs.

int firstButton = analogRead(A0);

We then create an if condition for when the input detects a large change in voltage.

if (firstButton >= 1023) {

We only want the program to send a keyboard key once per press, so we need another variable to stop the program from sending the key stroke continuously.

int numpadonePrevious = 0;

In the if conditional, we check if the numpadonePrevious variable is set to 0. If so, we send the keyboard key “1” and set the numpadonePrevious variable to 0.

if numpadonePrevious == 0) {
Serial.println(“1”); Keyboard.println(“1”);
numpadonePrevious = 1;
}
}

Now if we want the keyboard key to fire again after releasing the button, we need to set that variable back to 0 when the voltage drops.

if (firstButton < 800) {
if (numpadonePrevious ==1) {
Serial.println(“off”);
numpadonePrevious = 0;
}
}

An important part of this code is the dependency on the “Keyboard” library. So remember to include that when configuring your Arduino sketch.

Further Work