With my other LED reverse-engineering project waiting on a cable, I picked up an Alpha PPD220 (Personal Priority Display) LED Sign—probably the most basic model there is in their product line—off eBay at about 15% of the MSRP. (I’d prefer a Alpha 4160C, but I’m pretty sure the WAF (wife acceptance factor) wouldn’t permit it.) Alpha PPD220

Telling by the message that was still in its memory when I powered it on, this particular LED sign used to serve as a display at a lottery terminal somewhere in South Carolina. Within an hour or so of hacking away on some code from these guys, however, I was able to interface it using PHP and Perl—the latter posing as the messenger with the RS-232 serial interface—to accept messages from the public at large.

So, with that done, it was time to improve upon it. In between moments of helping my wife recover from all four of her wisdom teeth being pulled, I decided to build a library (from scratch) for the sign. Because of the shared protocol, the library I have in development should work with most, if not all Alpha and Betabrite models from Adaptive Displays, but I really can’t test that to verify beyond this basic little unit.

Here’s a bit of what it does in its current state:

  • Supports the Alpha 1.0 protocol mostly, with a little (untested) 2.0 and 3.0
  • Accommodates both paged sequences (AA-AZ) and PRIORITY Text (A0)
  • Synchronizes the system clock on the unit with the server automatically
  • Pulls in RSS feeds using Simplepie
  • Pulls in Current Weather and the Local Forecast via Yahoo’s API
  • Allows people visiting my site to enter messages without interrupting the flow of information (news, weather, time, etc.)
  • Added basic administrative functions (soft reset, speaker on/off, clear memory, etc.)
  • Added the ability to update a Twitter account with the last submitted message from the web. Sad.
  • Added the ability to notify me by email when someone submits a message. Doubly sad.
  • Updates every hour on the hour via a crontab which refreshes all the data

There’s still a lot of work to be done to maximize its utility (and for me to be comfortable enough to release it), but I’ll get to it as time permits. As it is, it’s become something far more useful than displaying lottery numbers and jackpot totals.

Want to give it a whirl? Feel free to check the sign out over here and drop a note while you’re at it.

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Posted on Sun, Jan 11, 2009 at 06:28PM

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