This circuit allows you to connect HD44780 compatible LCD modules to your PC via USB interface by using the virtual serial port implemented by FTDI USB chip.
Adding a cheap LCD module to your PC case mod is a popular and enjoyable DIY project for many beginners in electronics. Especially when we consider that most of the new computer mainboards are coming with no COM and LPT ports, this application will be essential for this purpose. FT232BM USB chip creates a virtual COM port. You can directly interface with your HD44780 compatible LCD with the help of CrystalFontz serial protocol and an LCD software such as LCD Smartie. An external programmable EEPROM is used to store information and settings.
You can also change the brightness and contrast since they are both connected to the PWM outputs on the ATTiny2313 microcontroller. Additionally you can power the backlight from USB port if it draws less than 400mA. AVR code is written in C, compiled on AVR-GCC and provided at the project page with PCB layouts.
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