LCD Display
LCD Display - 8 bits - Hitachi HD44780
Fig. 1 LCD Display
Description:
This board implements an alphanumeric LCD display, compatible with Hitachi HD44780 chip. It uses an 8 bits port, but interfaces with the display with 4 bits, so the 8 bits are enough to control the display (data and control lines).
The board will accomodate many types of display, from 1 to 4 lines, and up to 40 caracters per line. A jumper is used to enable the optional backlight.
The example uses a 4x20 display.
The board can be powered by 3.3 or 5V processor board, depending on the specification of the display used.
Specifications:
Input voltage 3.3 to 5V
Interface8 bits with processor
4 bits with display
Number of lignes1, 2 or 4
Nb of caractersUp to 40 per line
Schematic:
The display is connected in 4 bits mode. The 3 control lines (E, RS and RW) takes 3 bits of the 8 bits bus, and 4 are used for the data lines. The data lines are connected to bits 0 to 3. R2 is used to pull up RS, or bit 4. Bit 6 is E and 7 is RW.
JP1 and R3 enable the optional backlight. A jumper across JP1 will switch the backlight on or off.
The contrast is adjusted with R4.
Fig. 2 LCD Display schematic
Bit 5 could easily be used to drive the backlight of the display. A small NPN transistor could be used to switch it on or off. I haven't used it because I often connect the display to port A, and pin 5 is often input only.
Construction:
The PCB fits on a single sided board. All components are on the top side.
Fig. 3 LCD Display layout
Start with the 7 wire links, then continue with the lowest components, and finish with the display. The display can be mounted on some pin header, if it needs to be changed regularly.
Once all the components are soldered, you can test the board as described below.
Pads 1 to 4 can be drilled to 3mm to fix the board, or put spacers.
| LCD Display Component list |
|---|
| C1: 100 nF C2: 22 uF R1: 10 K R2: 100 K R3: 33 R4: Ajustable 1K DS1: Hitachi HD44780 based LCD display JP1: jumper 1x3 K1: Connector AMP MT 10pins male |
How to use / Testing:
To check the board, connect the board to an 8 bits interface and power up the board. When adjusting R4, you should be able to see some lines. This just checks the display is powered. Check the backlight with JP1.
To check the display itself, you need a processor board running the LCD tutorial. Don't forget to check and adjust R4 if the display is blank.
Files and links:
Eagle PCB and schematics files for LCD display.PDFs of PCB, layout and schematics of LCD display.
PIC Tutorials for LCD display.