NEW PROTOTYPE: USB Universal LCD backpack

The USB Universal LCD backpack controls LCDs with up to 16 interface pins at 3.3volts or 5.0volts. This includes common HD44780 character LCDs and larger graphical LCDs.

  • Small backpack mounts behind most LCDs
  • USB control for common 1×8, 1×16, 2×8, 2×16 … up to 4×40 character displays and some graphic displays
  • 3v3 and 5v LCDs
  • FT232R breakout, all pins to a header
  • 5volt backlight control with 500mA current limiter

This open source project was developed collaboratively in the forum. See it come to life here, and check out the design history and work-product on the wiki.

Available now for $15 at Seeed Studio. Each purchase at Seeed keeps the prototypes coming, thanks for your support!

Overview

The Universal LCD backpack is a dumb USB IO board, the computer does all the work of bitbanging data to the LCD. The back pack itself doesn’t have any intelligence and can’t control a display on its own.

This project is different than “smart” LCD backpacks that have a simple serial interface. Serial displays are easier to use, but the Universal LCD backpack is more flexible and can support many different displays. We designed it with common chips (FT232, 74HC595) so the parts are inexpensive and readily available.

An FT232 provides the PC-side USB connection. The FT232’s bitbang mode is used to send serial signals to the logic chips, and the logic chips put parallel output on the LCD pins. The 74HC595 is a more rugged interface to the LCD than the FT232 alone, and we get twice as many IO pins. The extra FT232 pins interface a backlight control with 500mA current limit.

The first batch is tested and available now for $15. PCBs in the first batch will be yellow.

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