Stan: FT232-based USB LCD backpack

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I have been experimenting with the FT232R as a USB to SPI interface. Some of it is on the web at www.chinwah-engineering.com.

After looking at the BP LCD interface I got to thinking that driving the LCD directly with FT232R is a bad idea and that using the '595 simplifies the software immensely. And so it follows that it would be possible to build a backpack for a LCD to run off of the USB bus. Sort of like the Olimex PIC-MT-USB but without the PIC. Should be a lot cheaper.

Contents

Forum

Development thread

Goals

  • Backpack (80x36)
  • USB
  • Simple/Low cost
  • Dumb requires host for programming
  • Support for the most common 1x16, 2x8 and some graphic displays
  • Support for 3v3 and 5v
  • FT232R breakout
  • Limit the total USB current to 500mA.

2x8 HD44780 pinout

HD44780 8x2 Header.png

Latest Schematic

USB LCD BACKPACK-5.png

Early schematics

USB LCD BACKPACK-4.png USB LCD BACKPACK-3.png

USB LCD BACKPACK-2.png USB LCD BACKPACK-1.png

PCBs

FT232R Backpack - Header Positions C.png

PCB size

The standard board size for a basic 16x2 character LCD display is 80x36 mm and has the 1x16 connector in the top left front. There are four mounting holes. There are a lot of variation in the sizes and connectors. Some even have the 1x16 connector at the bottom left but the pinout is 14-1,16,15 left to right. Some displays have the 2x8 connector but pins 1 and 2 have reversed voltage polarity. I think we should stay with what we have discussed and with a board size of 80x36.

Software

LCD pinouts

DisplayComparisons.png

This diagram includes pinouts for HD44780, SparkFun's 128*64 and [160*128], and Seeed's 128*64, but not Seeed's second 128*64.

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