Hi Guys,
First off, sorry that its taken so long to update this thread. Other work has kept me really busy.
Second, here is an update.
I hooked it all up to an arduino, threw it all in a cardboard box from the dollar store
and took it down to the sign to test it. Worked right off the hop. I've ordered a good plastic enclosure with a proper keystone jack for the ethernet and a dc port that can be screwed to the enclosure wall. It includes plastic wings for screwing it to the board in the back of the controller box.
Programming it was an absolute nightmare. While I was able to use the hardware SPI interface, the way the packets were laid out made them difficult to construct. I basically had to construct a bitmap for each of the characters. I then had to parse the time from the RTC and run through using a function that takes an X and Y position in the packet and uses the bitmap for the character to read and write bits in the packet to generate the correct time. I can post the source if anyone is interested.
Once it was up and running, they complained about the sign being too dim. Turns out it was running in the dim mode for night operation. Changing the first byte in the packet from 00000010 to 00000011 switched the sign into bright mode. The surrounding ambient light at night is so bright that I just left the sign in bright mode all the time instead of fiddling with the light sensor out in the -40c wind chill.
Thanks to everyone involved for their assistance. Admittedly, it was a bit much for me to bite off for my first project back into electronics repair but it all turned out ok in the end. I will update the thread again once everything is in its proper enclosure and installed in the box at the sign.
Photos attached.
Pictures below.