About the article

I2C Display

I2C Display
Pretty graphical simulators are all very well when developing circuits using microcontrollers, but sometimes there is no substitute for a proper display connected to real hardware. LCD panels based on the Hitachi HD44780 controller are popular as they are cheap and, at least in principle, easy to use. Unfortunately they require a large number of control signals, which in turn means bulky cables and losing the use of many of the microcontroller’s I/O pins. Here we present a solution to the problem in just three characters: I2C!
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info / Update


* Universal LCD module for microcontrollers
* Requires just two I/O port pins
* Multiple displays on one I2C bus
* Simple to use with AVR firmware

Component list
P1 = 5kO, SMD (Murata)
R2,R3,R4 = 1kO8, SMD 0805
R5 = 39O, SMD 0805 (see text)
C1,C2 = 100nF, SMD 0805
C3 = 10µF 16V, SMD (Vishay), diam. 4mm
IC1 = PCF8574 (PCF8574A) (see text)
T1 = BC807, SMD SOT23
LCD with HD44780 compatible controller
K1 = 4-way SIL pinheader, lead pitch 0.1" (2.54mm)
K2 = RJ11 socket, PCB mount
K3 = solder islands
J1,J2 = 2-way pinheader with jumper, 0.1" lead pitch
20-way pinheader, 0.1" pitch, for LCD connection
PCB # 080525-1
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