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Re: 32x64 LED monitor

PostPosted: Sun Sep 09, 2018 6:31 pm
by nanowaver
Have just seen these which look to be ideal for a 48 x 32 display.

https://www.ebay.co.uk/itm/P3-RGB-pixel ... SwrohZ4D1A

How easy are they to drive?

Baz

Re: 32x64 LED monitor

PostPosted: Mon Sep 10, 2018 12:03 pm
by Steve Anderson
It's often the headache with e-bay and the like, "How about some data guys?" They say it's 'generic', but generic to what?

I've Googled the part number and the vendor and got nowhere - I might be interested in these too.

About the only useful info I've found is it requires 5V at 4A (20W) and the data and control are parallel not serial. The two sockets are for 'daisy-chaining' more than one display.

Steve A.

Re: 32x64 LED monitor

PostPosted: Mon Sep 10, 2018 8:49 pm
by dominicbeesley
Hello, I'd start with this https://cdn-learn.adafruit.com/download ... matrix.pdf all the ones I got used something along these lines. I keep meaning to dig them out and get it all working again. I've been moving houses repeatedly this past couple of years and the LED matrix stuff is all packed up patiently waiting for me to get a workshop space sorted again, and the time!

Good luck an post to this thread if you have any questions, I'll try and rack my brains to remember how it all worked, if you'd like I can dig out my code - it was very specific to an arduino teensy using the ARM/SAM chip IIRC

D

Re: 32x64 LED monitor

PostPosted: Mon Sep 10, 2018 8:51 pm
by dominicbeesley
PS: I didn't use the RGB matrix shield but if I was to do it again I probably would, either that, or use some sort of FPGA or CPLD to do all the bit shifting...

Re: 32x64 LED monitor

PostPosted: Tue Sep 11, 2018 1:49 pm
by Steve Anderson
Thanks for the link Dominic - as mentioned there appears to be no datasheets or timing info 'out there', but it is a start. But I'm not going to rush into this as I have too much on my plate already!

Steve A.

Re: 32x64 LED monitor

PostPosted: Tue Sep 11, 2018 8:50 pm
by dominicbeesley
No, there's not much out there at all. I had a lot of trial and error to get things working. First getting anything to appear took me a while then there was a lot of messing to get decent gamma. There are delays in turning the LED's on (but seemingly not off) which mean that the faster you drive the array - you need to do this fast! - the dimmer things become so PWM needs some thought.

Also, to get the teensy arduino running fast enough I had to do some funky things like splitting the PWM data into "planes" that roughly corresponded to powers of two of brightness and then using timers/interrupts to output each row for a set time....it's starting to come back - it was tricky but it worked. The display was pretty good I mainly was then trying to do fancy DSP to decode colour and sync everything up in the not very long time left over after all the bit shifting.

I really ought to get it finished and bring in to a convention! Where does all the time go?

D

Re: 32x64 LED monitor

PostPosted: Wed Sep 12, 2018 5:00 am
by nanowaver
I'd be very interested to look at the code as I will need all the help I can get!

Baz

Re: 32x64 LED monitor

PostPosted: Thu Sep 13, 2018 11:39 pm
by dominicbeesley
Hi Baz,

Zip file attached, the main .ino is full of some very scary looking stuff that is to do with reading the ADC port using DMA to buffers and then trying to tweak the timers so that everything lines up with the syncs and lots of DSP stuff to do colour decoding.

The main stuff for driving the RBG matrix, which is where you probably want to start is in DomRGBScreen.cpp and .h

I'm afraid its all a bit of a dog's dinner. Give me a shout if its not clear

D

Re: 32x64 LED monitor

PostPosted: Fri Sep 14, 2018 2:01 pm
by Steve Anderson
"A dog's dinner." That brought a smile to my face - I haven't heard that expression in decades!

Steve A.

Re: 32x64 LED monitor

PostPosted: Fri Sep 14, 2018 11:12 pm
by nanowaver
Dom
Many thanks! I must get down to my homework after a hearty dog's dinner!

Baz

Re: 32x64 LED monitor

PostPosted: Sat Sep 15, 2018 1:52 am
by nanowaver
Dom

your code looks very impressive and much more sophisticated than my efforts so far - how do I send an attachment? I've tried both .ino and .txt files but they do not seem to be allowed.

Baz

Re: 32x64 LED monitor

PostPosted: Sat Sep 15, 2018 2:39 am
by smeezekitty
nanowaver wrote:Dom

your code looks very impressive and much more sophisticated than my efforts so far - how do I send an attachment? I've tried both .ino and .txt files but they do not seem to be allowed.

Baz


.zip files are allowed

Re: 32x64 LED monitor

PostPosted: Sat Sep 15, 2018 3:25 am
by nanowaver
Dom

see attached my feeble first effort!

Baz

Re: 32x64 LED monitor

PostPosted: Sat Sep 15, 2018 2:05 pm
by Steve Anderson
Zip files are allowed, there is a list of allowed attachment extensions that are valid. I'll see if I can post it here.

As you compose your message scroll down a little and you'll see a tab "Upload attachments" - from there it's pretty straight forward. Maximum file size is 20 Mb, you can attach more than one at a time, I've done 50 in the past.

Steve A.

Re: 32x64 LED monitor

PostPosted: Sat Sep 15, 2018 6:08 pm
by nanowaver
Many thanks for the advice about attaching files.

Baz