Microcontroller LCD interface using HD44780

This is doubtless the most simple way of hooking up a character based LCD display with a built-in HD44780 controller (and almost all character LCD displays are like this). The Vcc and Vdd are connected as usual, with the 0.1uF decoupling capacitor. For the contrast voltage a 10k potentiometer is used. Normally this has to be calibrated once, so a tiny one that you set with a screwdriver is good. The R/W is grounded, ensuring that the connection is write only (do NOT use a resistor for this. Quite some current goes through this pin, and not grounding it will cause the I/O ports to occasionally go into read mode, which will destroy your microcontroller, even if it is a PIC). The RS and E(nable) lines are hooked up to arbitrary pins on the 16F628A, and the D0-D3 are left disconnected. D4-D7 are connected to half a port of the microcontroller, in this case PORTA (RA0-RA3). Pins 15 and 16 are sometimes absent and are used to control the backlight. Regardless, they are left disconnected too.

Controlling this uses the 4-bit interface with maximum delays (it is not possible to use shorter delays, as it is a write only connection and there is no way of knowing whether the sent nybble has arrived). The software should show how it works. The initialization sequence is crucial, and I recommend copying it from the code, as it is easy to get wrong. When you see no characters appear, also fiddle with the contrast setting, as this could be set such that nothing displays.