Stan: FT232-based USB LCD backpack

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Stan: FT232-based USB LCD backpack
Codename Stan
Status Test production
Development development forum
ID # {{{id}}}

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

Resources

Goals

  • Backpack (80x36)
  • USB
  • Simple/Low cost
  • Dumb requires host for programming
  • Support for the most common 1x8, 1x16, 2x8, 2x16 ... up to 4x40 character dispalys and some graphic displays
  • Support for 3v3 and 5v
  • FT232R breakout (all pins)
  • Limit the total USB current to 500mA.

v2

  • jumpers to swap Vcc and Gnd at the JP3 and JP4

Prototypes

LCD pic-usb-backpack-board.jpg

LCD BACKPACK-ft232-test.jpg

Mini-back-ft232-test.jpg

LCD mini-ft232-test.jpg

LCD BACKPACK-ft232-bp.jpg LCD BACKPACK-pcbs.jpg

Latest Schematic

USB LCD BACKPACK-6.png

Early schematics

USB LCD BACKPACK-5.png USB LCD BACKPACK-4.png USB LCD BACKPACK-3.png

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

PCBs

pic version

Pic-lcd-bp-pcb.png

micro version

Mini-lcd-brb-pcb.png

mini version

Mini-lcd-bp-pcb.png


standard version

Usb-lcd-bp-pcb.png


older PCBs

Lcd-bp-pcb-v5.pngLcd-bp-pcb-v4.pngLcd-bp-pcb-v3.png

Concept drawings

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.

Test program

TestProgram.png


Software

FT232R outputs

SPI Screenshot.jpg


595 timing table

595-timing.png

LCD Addressing

LCDAddressing.png

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.

2x8 HD44780 pinout

HD44780 8x2 Header.png

LCDs tested/supported

Here we will list the LCDs we have tested with the LCD backpacks successfully and explain how to connect them if they can't be plugged into the backpack directly. We encourage users to add LCDs they have tested successfully with the USB LCD backpacks to this list.

A. LCD character displays (HD44780 compatible)

Character LCDs
FormatModel/Name Manufacturer Description Controller IC Notes Source
8*2 LMB0820DFC TOPWAY 8*2 character, white/blue KS0066 connects to 2x8 header JP3 Seeed Studio

ITead Studio

16*2 DEM16217 SYH-PY Display Elektonik GmbH 16*2 character, STN yellow/green ST7066U-0A-B connects to 1x16/24 header JP4,

pin 1-14 LCD --> pin 1-14 backpack, pin L+, L- LCD --> pin 15 (+BL), 16 (GND) backpack

reichelt

many others

16*2WH1602B-TMI-JT#040 WINSTAR 16*2 characters, white/blue S6A0069 connects to 1x16/24 header JP4 Sure Electronics (DE-LM201)
20*4LMB204BCF TOPWAY 20*4, white/blue, white LED backlight KS0073 connects to 1x16/24 header JP4 Seeed Studio

ITead Studio

20*4JHD204A 040319 REV 1.0 JHD (?) 20*4, yellow/green, yellow LED backlight, cheap generic LCD unknown connects to 1x16/24 header JP4 eBay

B. LCD graphic displays

Little engineers

Little-engineer.png

Manufacturing test plan

Ft232-LCD-attach.jpg

  • Connect a HD44780 LCD to the backpack as shown
  • Place a jumper on JP1 to select the backlight ground (usually GND to GND), the inner two pins
  • Place a jumper on JP2 to select the LCD power supply, usually 5.0V
  • Plug in the USB cable

Ft232-LCD-test-app.png

  • Start the LCD application
  • Choose the display size from the Display drop-down menu
  • Select backlight->on to turn on the backlight
  • Type some text in the box and click Enter Line 1 to display it on the LCD

If the backlight is enabled, and the text displays, then the board should be fully functional.