How To LCD connections, basic setup

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

It looks like you have a 1K resistor going from the contrast pin to +5v,
and that's the entire contrast circuit. If so, that's not correct.

You should change it so there is a 1K resistor going between the contrast
pin and ground, and also a 10K resistor bewteen contrast and +5v.
This will set the contrast pin voltage to approximately 0.45 volts.
You should check it with a voltmeter to confirm this.

You should also check all the connections between the PIC and the LCD
with an ohmeter. Turn off the power and put one probe on the PIC pins
and the other probe on the LCD pins, and go through each set of pins
to verify the connections. You have three sets of wires, and at least
four connectors to be concerned with. It should be checked.

Here is a schematic of the contrast circuit.