Mac OS X USB LCD
Sunday, April 24th, 2005
I’m working on a small project which will allow you to connect a small LCD to your Mac via USB, and I’m curious if people have any suggestions as to what they would use it for — current iTunes track, unread mail, RSS headlines? At right you can see an image of the circuit I’ve put together. The chip on the left is a Cypress USB interface from Delcom Engineering, and the one on the right is a standard MAX232 chip, which converts signal levels to RS-232 from the Cypress chip. Using these two together, you can send RS-232 data from your Mac, and I’ve connected it to a serial LCD from Scott Edwards Electronics (the most expensive part of the project), and am able to send any data to the LCD, even control the backlight!
I intend to build up a full page about how I did it in the very near future, but I’m still working on the C code which does the work of talking to the USB I/O chip. Right now, though, I’m looking for suggestions of things to implement for the release. If you have a neat idea, post it in the comments. I’ll be working with a 4 line by 20 character LCD, if it helps.
Update: Also, if anyone has a preferred way of getting data to the LCD, post that as well. Would you prefer AppleScript, Python, something else? I’m sure AppleScript will be involved somewhere along the way to communicate with Mac OS X apps, but what about the “glue” between that and my command-line app? I’m partial to PHP, but it’s not used very often as a system-level scripting system.
One of my favorite behind-the-scenes programs for Mac OS X is a network filter called Little Snitch. It allows you to limit any outbound network connection that your Mac makes, and permit or deny it based on the server address, port, or both. For example, if a new program tries to connect to the internet send data out to a server, Little Snitch pops up and asks you what you want to do. At that point, you can allow or deny the connection once, forever, or until the application quits.