LED matrix electronics donation?


#1

I’ve got a lot of new RED LED clusters 8x8 and 8x5 from China Semi which have been sitting at work since the late 90’s / early 00’s that we just want to get rid of to make space. Also, there are several assembled and bare PCBs for a scrolling message display application. Can I drop these off somewhere as a donation? How does that work?


#2

There is always the “Freebie” shelf. Short of that, these items sound distinctly electronics related. As such I’m tagging the committee chair @artg_dms.


#3

If Art doesn’t want them for the space, I’d love to take them.

I’ve been working on a project to convert the Golden Tee Tournament LED signs that were tossed aside by the pallet load by arcade operators to run using the Arduino Nano and a handful of common components.

RJ


#4

I can actually help to pin out the headers so that people would know how to control these signs.

As a slightly more aggressive project, I have a pretty dense LED matrix character display that we are tossing as well. It isn’t seamless, so it would only be good as a text info display (think movie theater ticket counter display or airport flight / gate info).


#5

Sounds cool :slight_smile:


#6

I have worked with these things before and would love to collaborate on projects using them.


#7

Electronics will take them.
Could be some interesting class builds/demos for the LED SIG.
What we don’t need can go to the donation.shelf.
Include documentation if you get it.
Do you need a receipt for taxes?
Thanks!


#8

Great! A receipt would be nice, but is not necessary. Let me know how to proceed. Just to set expectations, we are not talking about a shipping container of parts. There are about 7 boxes which will not totally fill the bed of my small pickup truck.


#9

I’m also bringing a few assembled and working signs. I do not know how to update them, so in order to be useful, you would have to swap the controller for a BeagleBone or Arduino.


#10

Drop them off in the ELab.
Stack some under the center table, the rest on top.
I’ll start the paperwork.
Suggest taking picts of the stuff for your records.
Thanks again!


#11

Interesting! @childofthehorn and I ran a successful Kickstarter using 5*7 red/green LED matrices, probably much like yours. We manufactured PCBs to mount the panels (Displayboards) and to handle power & communication (Partnerboards). The LEDs are driven over RS232/TTL with a custom data protocol using an ATmega168, which was specially picked for its pin count & ability to drive relatively high current from its pins without needing driver transistors. My panels are the mid-sized dot pitch, maybe 0.75cm in diameter, leading to a PCB of 1.45" * 2.1". I have a box of mondo-sized red LED panels that are twice as big in both dimensions that could be fun to play with too, but you definitely need drivers for them to work nicely.

Anyway, here’s the project: https://github.com/ledgoes/
And the campaign (an old relic from a by-gone era by now): https://www.kickstarter.com/projects/558452768/ledgoes
And the website: www.ledgoes.com


#12

@Team_Electronics Is anyone interested in developing a class using these? I can lend a hand.

If no one picks up on it, I will look into doing one. My interest would be an intro level class similar to my Arduino classes. One or more advanced classes would be very appropriate as well.


#13

There are a number of LED strips that have 8x8 led matrix dsplys. 8 to a strip. Strip has decoding and serial in for scanning. Has 5821a serial to parallel open collector drvrs. Strips can be placed end to end to make that long scrolling dsply you suggested for the new ELab!

One of our committee members has traced out the connector. A full schematic shouldn’t be to hard to do. There are also blank boards we can assemble.


#14

I’ve submitted three classes that will hit the Event Calendar tomorrow and presentations need to be updated. I’m also working on a new class. I hope someone will do classes/projects with these 8x8s. If not, I’ll look at it in a couple of weeks.


#15

This is great that everyone is getting excited about these! I hope that they end up being useful at the space as signage somehow.

I’m super-slammed at work right now, so I don’t have a lot of bandwidth to help do anything with them at the moment. I did actually publish an extremely basic Linux Kernel Module to drive one of these LED message signs here:

The problem was, as many have lamented, Linux is not a real time os (RTOS), so the display showed visual artifacts (stuttering).

So, using a BeagleBone Black, I created a PRU driver which provides excellent performance, however I found developing c code for the PRU very challenging since there are two incompatible ways of doing it. TI is deprecating one way in favor of the other. It’s a long story. I have not published my PRU code since it is not totally complete, but could if anyone was interested.

Much inspiration was taken from here:

Be advised that the LEDscape project coded the PRU is assembly, which is not too hard, but I didn’t try to get into it deeply.


#16

It doesn’t look that hard…


#17

What’s frustrating Bill is there’s a lot of info out there using the old PRU method (and that link is one of them).

The PRU’s in general aren’t too hard to get up and running, but communicating between the two PRU’s for instance has proven a lot harder than it should be IMO. I feel like BB’s would much more popular if TI had provided a “mortal friendly” SDK at some point. :wink:


#18

@Kentamanos is right. The issues is with prussdrv.h, which is the old method of loading the PRU with code. The new method is called rproc and is a fancier method with message queues and whatnot, but it is a little bit difficult to get straight answers about how to do basic things. To make matters worse, if you do not use Code Composer Studio, it is that much harder. I was trying to do everything on my main machine, which is running Debian. I got a working solution, but sometimes I would do something that would cause the code to stop working, and debugging in my environment was non-existent.

While looking around just now, I found this which I want to dump here for future reference:
https://elinux.org/EBC_Exercise_30_PRU_via_remoteproc_and_RPMsg