Notes on the pinouts and implementation
The controller has an onboard power supply (Vee) for the LCD contrast. By connecting a 20k POT between Vee (Pin 18) and 5+v Vdd (Pin 2) with the pots wiper connected to Vo (Pin 3) one is able to adjust the LCD’s contrast. Pins 19 and 20 are the cathode (K) and anode (A) of the backlit led. One should insert a 100-200 ohm resister in series with the anode to provide overload protection.