Please beware that 95% of LCDs will reference their Vee to the Vcc. When you look at the data sheets the Vee requirement is often specified as a negative voltage number with respect to Vcc. If the spec says that Vee needs to be -5V then for a display operating at a Vcc of 5 volts it is sufficient to attach the Vee to GND.

I rarely design an LCD module into a product without providing a voltage below ground to which Vee can then be biased. I most often have a software / hardware provision to produce Vee in a variable manner from say 3V to -5V to permit user adjustable and/or temperature compensated contrast adjustment. A PWM works nice for this feature. A small I²C D/A converter part or an SPI digital POT also can provide the Vee adjustment.

Michael Karas