Mobile Lap Timer for Track and Field Events
I happened to have an old AMS (Betabrite) LED marquee sitting around, so I decided to configure it as a large readout. The sign is controlled via rs232 with an Arduino RBBB. A Betabrite sign can read/write text, dots, strings, or configuration commands. A text message is the easiest to configure and is a good starting point (see resources below for examples). However, the sign will blink every time a text message updates. The sign blink isnt a problem for things that update infrequently, but it becomes annoying for a clock (that updates once a second).
Strings are designed to be rapidly updated, but are more challenging to implement.
Here is the basic sequence for using strings:
1) A space in sign memory is allocated for a string.
2) A text message is saved in memory. This message will call the string as a variable. (e.g. Text:The Temperature is XX degrees Celsius, String: XX = 12)
3) A string is sent to the sign, every time display data updates.
See my string example code for an implementation for Arduino.
Resources
I came across a few good resources that covered interfacing with Betabrite signs:
Good resource for basic hardware configuration (cable fabrication and test code)
http://www.i-hacked.com/content/view/225/90/
Someones test code (good for verifying cable integrity)
Helpful discussion of Betabrite communications protocol (useful example code)
http://dens-site.net/betabrite/betabrite.htm#basic_proto_overview
Another discussion of Programming LED signs
http://wls.wwco.com/ledsigns/alpha/protocol.html
Here is a copy of the Alpha Sign Communication Protocol. The manual is a bit cryptic at first, but there are a few good code examples.