Let's take a tour of the pins! Starting with the top control & power pins...
- RS - this is the reset pin. To reset the module, pull this pin to ground. It does not affect pairing.
- L2 - this is the same output that is connected to the Pair LED. If you want to put this in a box and have an external Pair indicator LED, wire an LED from this pin, through a 1K resistor, to ground.
PB - this is the pair button pin. It is connected to the button onboard that is used to reset the pairing. If you want to make another, external pair button, connect a switch from this key to 3V (not ground!)
- L1 - this is the same output that is connected to the Key LED. If you want to put this in a box and have an external Key-press indicator LED, wire an LED from this pin, through a 1K resistor, to ground.
- RX - this is the UART input, used if you want to send UART->Keypress data, or re-map the buttons. It is 5V compliant, use 3V-5V TTL logic, 9600 baud.
TX - this is the UART output, used for watching debug data or re-mapping the buttons. It is 3V logic level output.
This row is easy, it is 12 individual pins that connect to a switch that will trigger a keypress. Each pin has a pullup resistor internally to 3V. To activate a keypress, connect the pin to ground. When it is connect to ground, a KEYDOWN is sent, when it is disconnected, a KEYUP is sent.
Do not inject 5V into these pins! They connect directly to the BT module which runs at 3V.