NEW PROTOTYPE: USB & serial LCD backpack
Small character LCDs can show new mail stats, system performance, news feeds, and more. The USB and Serial LCD backpack connects HD44780-compatible character LCD screens to your USB (or serial) port.
Almost every open source hardware shop sells some type of serial LCD backpack. Our goal is to build an update to the classic serial LCD backpack, something better suited to a USB-centric world:
- USB control, upgrades, and power are a must. This backpack has a USB connection via MINI-B jack, and a USB breakout header for easy connections inside a computer case
- It still supports the simple 5volt serial control found on other LCD backpacks
- Software backlight dimming, optional software contrast adjustment too
- Extra pins for buttons and inputs
- Support in popular open source LCD apps like LCD Smartie and LCD Proc
- Same price as other serial-only LCD backpacks!
This was one of the most popular free PCBs ever. Now you can get one assembled for $16.95 at Seeed Studio.
Hardware design overview
The LCD Backpack uses a PIC18F2550 8bit microcontroller (IC1) with USB. It’s powered directly by the USB 5v supply. For extra protection, we added a 500mA fuse (F1).
An HD44780-compatible character display, with our without backlight, connects to the long header on the edge of the PCB. The LCD backpack uses the full 8bit data mode, both read and write are supported.
Adjustment
A 100ohm potentiometer, labeled BACKLIGHT, adds a resistor to the backlight if your LCD needs it.
The backlight is software dimmable. The PIC hardware pulse-width modulator controls the backlight through transistor (T1) with a 1K base resistor (R2).
Screen contrast is adjusted through a 10K potentiometer (CONTRAST). An optional hack enables software contrast adjustment. We didn’t know if software contrast adjustment would work for every LCD, so we used a solder jumper to make it a hackable feature.
Read the complete hardware design overview.
Works with LCD Smartie, LCD Proc
LCD Smartie is a Windows application that shows news, email, system information, and more on an external LCD screen. The USB and Serial LCB backpack works with LCD Smartie in ‘Matrix Orbital’ mode. LCD Smartie is free, open source (GPL) software.
See LCD Smartie configuration instructions.
Linux users can check out LCD Proc.
Get one
Get one for $16.95 at Seeed Studio. Get USB and the latest features for the same price as a serial-only LCD backpack.
- USB and Serial LCD backpack home page
- Hardware design overview
- Firmware updates
- Command protocol
- LCD Smartie configuration
Comments
What are the connections at the bottom of the board? Are there silk screen labels on the other side of the board? Can you include a picture of the other side of the board, please?
Hi Michael,
Here’s a picture of the back of the board:
http://dangerousprototypes.com/docs/File:Lcb-bp-back.jpg
All the pins are named on the silk.
The connections on the bottom are two IO for buttons, 5volt serial for normal serial control or extra IO, and access to the USB signals for connection directly to a computer motherboard.
Michael, if you look up higher on the page it gives all the pin outs and what they do.
Thank you Gentlemen. That’s an incredibly nice looking board…
It was the most popular free PCB (and most built) ever :)
Really?
OMG! Popular than BP!!!
This is very nice DP. Parallax sells a far inferior 4×20 serial LCD for $40! What a rip-off. PWM back light control is a must, thanks for that. Off to Seeed…
Great work at a really affordable price!
What about to extend the circuit/firmware so it could be able to control also 4 x 40 displays?
The most common commercially available models of 4 x 40 displays have 2 independent HD44780 (or compatible) LCD controllers onboard; they share the data bus, RS and R/W control signals but the Enable (E) signal is duplicated (that is there are 2 independent E lines, one for the first 2 rows and 1 for the other 2 rows).
From the schematic diagram I see that some I/O pins of the MCU seems to be free and I think that the firmware can be easily extended to support another E line.
Also, at the price of a small increment in size of the PCB, I think it could be a good idea to include the other standard form of display connector, that is the 2 x 7 one.
Francesco, Italy