Tag Archives: Serial LCD


This serial LCD module gets power and data through one wire

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I found this interesting post on EDN by  about driving an HD44780-based LCD module serially through one wire. It receives the display data as well as power supply through the same single wire connected to the UART TX pin of the host microcontroller. The LCD module itself uses a PIC12F508 microcontroller that receives the serial data from the host MCU and transfers it to the LCD in 4-bit mode. The clever trick in this design is during idle condition, the UART TX output from the host MCU remains high, which is used to supply power to the PIC12F508 MCU and the LCD. During the data transmission, a simple capacitor and diode circuit is used to continue providing the stable DC power to the LCD and PIC MCU.

1-wire serial LCD

1-wire serial LCD

Serial LCD Module using PIC16F88

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A varieties of serial LCDs from different manufacturers are available in the market. But if you are good at PIC programming you can make one by yourself. The most popular and low cost LCDs for embedded projects are HD44780 based character LCD modules. They are parallel LCDs because they recieve display data from microcontrollers in parallel format. Their interface require at least 6 I/O pins of a microcontroller. By including an additional microcontroller to your HD44780 LCD module you can convert it to a serial LCD. The idea is very simple. The extra controller will receive the display data from the host microcontroller in a serial format and provide it to the LCD module in an appropriate parallel format. With the new LCD module, you would be able to send the display data with just one wire.

Here’s a project that uses a PIC16F88 microcontroller working as a display controller for serial to parallel conversion of display data. The demonstrating software is written in C and compiled with mikroC.


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