Slashdot Mirror
LED displays with Linux?
Timothy asks:
"It seems that everywhere I look I see articles about Linux/chickenwire
based MP3 players for cars that utilize a LED display instead
of an actual computer screen for outputting track information and such.
My question for you is simple: where can I find information on buying/using
a LED display in Linux. Where can you buy them, what's an
average cost for one (so I could gauge what's listed)? Would it hook up to
a serial/com device? Do you need a special card to
interface it into a computer system? How would you go about writing
information to the LED and such?"
I have interfaced Linux with a Pro-Lite LED Sign Board for use as a message board at a radio station. The interface is Simple! It connects to the computer via a serial port and accepts simple ASCII character commands for programming. In fact, you can go to their website and register to have them email you the ASCII command set. It seems to work great! If you need more information , write me at andrew.bunker@ksl.com
LEDs are 'Light Emitting Diodes', the most common choice for any little blinking light on your computer (they tend to be just a little colored light.)
LCD is 'Liquid Crystal Display' which has this liquid crystal that's polarized and changes polarization when some electricity is run through it. This is what's used on digital watches, calculators, laptop displays and the little linux based MP3 player thingy that I've seen before.
If you're interested in the former, look on metalab (ex-sunsite) under Linux/system/status you'll find that there is a led-stat.txt describing a short program and cable with LEDs, etc. (there's also a ledstatus tarball and lsm) You can modify this LED status program in a number of ways, at one place I worked we had it set up with a colored "load meter" (gets higher when more load) combined with a heartbeat (goes back and forth to give you a 'feel' of how much CPU is available) and with two of the parallel port pins hooked up to a relay hooked up to the reset switch of the NT machine next to it, so we could send a specific signal to lcdmeter and reboot the NT machine when it froze.
If you're interested in an LCD display panel, as I suspect you really are, Matrix Orbital Corporation makes a series of LCD display panels (also VFD (Vacuum Fluorescent Display) modules that appear to be completely compatible and brighter than the LCD panels) that are sold through a few different channels, including Linux Central. These appear to use RS-232, (or I2C, whatever that is) so you'll need a spare serial port.
The software to drive these is LCDproc which works on a fairly configurable client/server interface, so it should be possible to display anything you want with LCDproc as long as you can write a client that can speak the protocol.
If you're looking for a cheap way to get an LCD running on your system, check out the Sanyo DM016Z at this place (scroll down-near the bottom). It's a 2x16 character backlit LCD that uses the industry-standard Hitachi HD44780 controller for only USD $5.99 + S&H. You may also want to purchase the lcd cable for $0.99 if you want to make life easier. There are also links on the page to schematics to show you how to connect the device to a parallel port or serial port.