USB to LCD as Message Pump

Overview

This backpack device allows an LCD display to connect directly to a computer using a PIC microcontroller to drive the LCD, and a FTDI USB to serial chip to connect to a computer.

Explanation

Creating a virtual com port (VCP) makes the FTDI chip to work wherein the opening of VCP to the Message Pump, the LCD will display any ASCII serial data sent to it. The messages will be displayed on the Message Pump as long as the computer can access a serial port. Opening the Hyper Terminal or other terminal software is the easiest way to use the Message Pump. The COM port for the Message Pump is selected and opened before typing.

The Message Pump is using surface mounted parts where they are soldered at through holes. The FTDI USB chip is the most popular part used in this project. A current limiting resistor needs to be added to either R4 or R7 if the display has back-lighting feature. R4 is a SMT resistor while R7 is a standard through hole resistor. 

MOSFET Q1 turns OFF the power to the display and PIC if USB bus goes into suspend mode.