Information for using small character LCDs such as the HD44780 with Mac OS X, LCDproc and Growl. And other Apple and Mac USB stuff.

Thursday, May 26, 2005

LCD Software

So, I am continuing to develop some software for the display.

Here are the priorities:

  1. Develop simple user-space code to access the parallel port functions. - Almost finished.
  2. Develop some simple code for running the HD44780.
  3. Write a small interactive Cocoa application to output data to the LCDs
  4. Write a display plug-in for Growl.
  5. Finally, create a kernel extension for accessing the parallel ports through Apple's IOKit. This may become an open source project, or maybe even part of Darwin.

Wednesday, May 25, 2005


4 line LCD

2 line LCD

What makes this so interesting is that this particular cable only works on windows, and the mac version does not work on Mac OS X, and either one will only work with printers.

Just to recap, this is USB -> parallel -> LCD,
not USB -> Serial -> parallel -> LCD.
And all for under $20!!

Tuesday, May 24, 2005

It works!!!

So I got it working!

Images to come....

Thursday, May 19, 2005

PL-2305 chip not working out

I have been trying to use the Prolific PL-2305 USB to parallel chip to get this done. Unfortunately, the data sheet does not mention the vendor-specific commands required to properly control the parallel port beyond simple printing. It only mentions that the commands exist, Prolific tech support has not responded, and reverse engineering the chip has proven beyond my patience.

Fortunately, Lucent makes a chip, the USS720, which I am already using in my Belkin printer adapter. It will be much simpler to implement since the vendor-specific commands are well documented. Unfortunately, they are a little more expensive, and more difficult to find. They typically appear in name-brand adapters. Either way, they aren't too expensive, and it is worth the time saved.

Wednesday, May 4, 2005

LCD source

I found a cheap source near my home for LCDs and got everything hooked up through the usb adapter. The LCDs displayed the black bars which indicate that the LCDs are getting power and work correctly.

On the software side, I have connected to the usb module, but commands aren't getting to the LCD apparently due to some flakey wiring. Once I get that worked out, I will post some pics.