Adding external switch for LCD Keypad Shield

Hi there, i am using a LCD keypad Shield with Arduino Uno. I want to know is it possible to add external switch as an input beside using all 5 push button on the LCD Keypad Shield? Kindly reply. :slight_smile:

OK. Here is the schematic:

Note that the buttons connect from pin A0 to ground.

To connect an external button, connect one side to ground, and the other to a resistor which either matches the (sum of the) corresponding resistor(s) on the board, or a different value that you can detect in your sketch, to the A0 pin.

A quick calc indicates a standard value is 6800 ohms for the switch series resistor will work fine with a threshold of <945. This maximises the noise/tolerance margins in the remaining ADC range to about 75.