LED Marquee – Part 3

Soo, the project has been dead for about… well 2.5 years now 😯

I recently got the time and reason to continue, as a i have an EE course called “Advanced MicroProcessors” where we have to do a project and want to use the display.

I scrap’ed the idea of revers-engineering the controller board and jumped straight to the protocol between the controller and the daisy-chained LED driver boards.

Preliminary continuity tests between the bus and component on the board gave me an idea about the pinout of the connector.

Poking around with my Logic16 gave my some understanding as well, but not much.

After this i threw in som single wires (i forgot the term) in the connection. (all hail AliExpress for saving me the work of doing these plugs by hand!)

led8_l

 

Anyway…
With this i could start pulling wires to see what effect they had on the display in relation to my preliminary pinout.

What i saw on the logic analyzer seemed noisy, but i wasn’t sure if it was noise or not as i could only do 100 MHz on a single wire on the Saleae. And so i hooked up a 20 y/o logic analyzer that had been sitting on a shelf at my school for years.

led9_l

After spending half an hour getting it to boot it from floppy-disks, we realized how much of an improvements modern GUI’s are over old gear and we gave up on it!

Back to the Saleae:

led12_l

 

led13_l

 

I had eight lines that seem like data lines and 24 that clearly controlling the 24 lines of the display, but the communication on the data lines still didn’t make any sense.

I’d been searching for some sort of clock for the data and found it after realizing the i had placed a hook wrong, eureka!

There was a _lot_ going on on the display lines when the clock was flat, and on the assumption that it did not affect i programmed up a ATMega324P with som basic code…

led14_l

One line working!!!

A few more hours fiddling around with the code i had a working display with a static image and a frame counter!

led15_l
Now we’re ready for the actual part of the AMS course, doing some proper MCU work!

EDIT: Logic screenshots coming!

(And up untill now has been what i moved from the old HaD forums! Any further stuff is new)

 

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