i've bought some simple foil / membrane keypads but unfortunately there's no documentation (and i'm a hardware noob). Note this is not a matrix type keypad, it seems there's a dedicated wire for each button.
It's a simple strip with 5 buttons and a LED. The foil cable has 7 wires.
My question: how do i connect this, so i can control the LED (GPIO output) and read the buttons (GPIO input)?
I took my multi-meter to measure conductivity between the pins. i found the 3rd pin is common, i.e. if I hook one wire of my multimeter to it I can check which of the other pins corresponds to buttons. Using this approach I mapped wires to buttons, leaving one pin which is connected to the LED. Not sure if there's a resistor in there, so I've not hooked it up yet.
Now the issue: for the buttons to work, I connect the common pin to Vcc and the button pins to GPIO inputs. When i press a button, Vcc is conducted to the input pin and a button press is registered. But for the LED to work, i need an output pin and ground(?), but i have only one pin left.
Am i missing something? Does this need more hardware or is the LED not supposed to be controlled by a GPIO pin?