Testing touch sensitive inputs

Before you start writing code it’s a good idea to check that your touch sensitive input keys work. PiFace Emulator is ideal for this.

  • Start the emulator by double clicking the icon on the Desktop or by typing piface-emulator in a Terminal.
  • Disable the ‘Enable pullups’ feature of the PiFace, by turning off Input Pullups from the Enable menu in the emulator. (Untick ‘Input Pullups”)
  • Hand holding wire from PiFace ground terminal
    Disabling the input pullup resistors

  • The emulator shows how the Raspberry Pi is interpreting the inputs keys with dots on the corresponding input terminal. Without holding an object, no inputs should be shown. If a yellow dot is shown then it is most likely the 33Mohm resistor is not connected to 5V properly.
  • Hold the ground wire and touch an object. The emulator will register this by showing a dot on the corresponding input. If no input is registered then check your wiring. You can try touching the ground wire directly to the input terminal to check it is registered and then work methodically along the wires to check there is a good connection.
  • Diagram of how to wire the PiFace for touch sensitive inputs
    Diagram of PiFace wired for touch inputs