Tuesday, 5 January 2016

Spectrum/Alpha 4160c LED message board

Im sure you've all seen them, those scrolling LED message displays in shops and offices. Well, I have one, seemingly in working order other than a big chunk knocked off of the end of the case (I have the chunk so thats an easy repair!), acquired from scrap.

But I have a problem. I dont have the correct firmware version to allow me to actually interface to it and make it work! So the hunt is on to find the firmware. The manufacturer wants an extortionate price for an EPROM, so that route is out. At present then im looking at the possibility of reverse engineering it to bypass the built in computer. This would mean a drastic loss of capability, but then just how many ways do you really need an LED sign to scroll, fade, etc?

The EPROM is a 27C1001, which is a 1Mbit (128k x 8) device, so clearly the firmware file for this machine is pretty hefty!

The actual sign is made up of five boards (one of which has the computer piggy-backed to it), each containing the driver capabilities for two rows of five 8x8 bicolour LED matrix units. The driver electronics look to be pretty standard - hex buffer/driver logic, and shift registers.

Heres one of the boards, ive had this one out whilst I metered out the LED matrix pin-outs -

Im not overly impressed I have to say with the power connection in the middle of the board! A proper high current low voltage bus would have been a much better idea!

If I can find a way to get this working, then it will be available for use by the Lions club for any events etc where it would be useful.

1 comment:

Jordan said...

Awesome to see the inner workings of stuff like that! I bet this is really fun to work with.