Control and Power a 16×2 LCD Display with Only Two Wires




You’ve probably seen or used generic 16 x 2 LCD character displays in various electronics projects. While they do a good job of showing text as needed, they require four data lines, two additional control pins, and +5VDC and ground lines as well. If this was designed today — as Vinod S. notes in his LCD simplification project write-up — connecting such a display would only take a single wire for data, or perhaps a pair for I2C or TWI.

To correct this shortcoming, Vinod came up with a solution that uses not one or two wires, but no dedicated data lines — instead transmitting data and power through the same wire. Part of the trick here is that he’s using an Arduino Pro Mini as a translation device, taking in signals from his computer via the power/data line, then pushing out parallel signals as necessary to the display.

The even more clever part of this setup is the use of a p-channel/n-channel MOSFET circuit to take signals from a USB to UART converter, then resolve it into a combined power + data output line. When the power rail is pulled to zero, the Arduino is able to sense this input; however, a diode and capacitor keep the instantaneous power supply to the LCD constant enough to prevent it from blanking out. Check it out on display in the video below.


Control and Power a 16×2 LCD Display with Only Two Wires was originally published in Hackster Blog on Medium, where people are continuing the conversation by highlighting and responding to this story.





Original article: Control and Power a 16×2 LCD Display with Only Two Wires
Author: Jeremy S. Cook