USB & Serial LCD backlight and contrast adjustment
The adapter features software and manual backlight adjustment. Contrast is adjusted manually, but an optional hack can enable software contrast adjustment.
The backlight is software dimmable. The dim command sent from control software sets the backlight brightness.
A 100ohm potentiometer labeled BACKLIGHT can be used to add a resistor to the backlight if your LCD requires it. Please check the datasheet to see if a resistor is required.
LCD contrast is adjusted through a 10K potentiometer.
Software adjustment hack
An optional hack can enable software contrast adjustment. We didn't know if software contrast adjustment would work, so we used a solder jumper to make it a hackable feature.
Cut the trace between pads 2 and 3 of the solder jumper (SJ1). Next solder pads 1 and 2 together. The PIC's second pulse-width modulator (CPP2) is now the power source for the contrast. This is largely untested.