Can I set individual chain length ? Will one RPI 4 be enough for 50 panels ?

[GeorgeFlorian]

Hello !

I have a project that involves a big display, composed of 5x10 panels.

I would like to know if I can do this with only one RPI 4 and, since 50/3=16.6, what should the chain_length value should be ?

I am confused by the U-Mapper scheme.

Considering that the panels are pointing UP and looking at the back of the panels, the Input is on the left-side and the output is on the right-side. So, turning them around and looking at them from the front, the input will be on the right-side. As such, a chain will should like this:

   [<][<][<][<][<]↑  }--- Pi connector #1
   [>][>][>][>][>]↓
   [<][<][<][<][<]↑
   [>][>][>][>][>]↓
   [<][<][<][<][<]↑  }--- Pi connector #2
   [>][>][>][>][>]↓
   [<][<][<][<][<]↑
   [>][>][>][>][>]↓
   [<][<][<][<][<]↑  }--- Pi connector #3
   [>][>][>][>][>]↓

Looking from the front:

• First row is comprised of panels pointing UP with the input on the right side
• Second row is comprised of panels pointing DOWN with the input on the left side

First and second chain should have 20 panels each and the third one 10. I will use pixel_mapper_config = "U-mapper"; and parallel = 2. But what should I write at chain_length ?

I will be using an active adapter.

The cables from a row's first panel to the adapter's connector will be very long. I have read something you wrote in a thread:

If possible, go back-and-forth rather than starting from the start with each chain. That way, you keep cables short. So
    ->  -> -> -> |
    <- <- <- <-  v

But I don't understand what you mean.

What do you think ?

Thank you !

[shanerooni]

did you ever figure this out? i'm trying to create a chain of 12 panels in a 3 rows x 4 columns configuration with 32x64 panels. i read something about an "s-mapper", but i'm also reading that "parallel" only works with the chip board that has 3 outputs. i'm using an adafruit hat, so i need to run everything off of 1 continuous chain of 12. thanks!

[hzeller]

you want to run them parallel using one of the parallel adapters, the single chain adafruit hat will result in too low of a refresh rate for 12 panels. You can test the expected refresh rate by running the program with the necessary options and outputting the refresh rate.

[shanerooni]

i actually am running all 12 at once right now, and don't see too much of a refresh rate issue. i'm just using it for a MM:SS timer for a kids running series, and maybe to scroll a few announcements. i snaked them as shown above, basically:

'<<<< - pi4 '>>>> '<<<<

i'm just not sure how to get it to read the panels in the correct way with the mapping. where can i find an adapter? does it take the place of the adafruit hat on the 40 pins? thanks!

[shanerooni]

This is a quick video with the image scroller. I have some flicker, and I'm planning to write the two leads together I saw mentioned in another post.

On Fri, Mar 6, 2020, 5:25 PM Henner Zeller notifications@github.com wrote:

you want to run them parallel using one of the parallel adapters, the single chain adafruit hat will result in too low of a refresh rate for 12 panels. You can test the expected refresh rate by running the program with the necessary options and outputting the refresh rate.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/hzeller/rpi-rgb-led-matrix/issues/904?email_source=notifications&email_token=AGJKW7XTQOSAXM6RHVYAWWLRGFZ7BA5CNFSM4I5OGFL2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEODBUPA#issuecomment-595991100, or unsubscribe https://github.com/notifications/unsubscribe-auth/AGJKW7SLWXWAAUR3KH7TY7TRGFZ7BANCNFSM4I5OGFLQ .

[hzeller]

Check out the page that describes the adapters https://github.com/hzeller/rpi-rgb-led-matrix/tree/master/adapter There is also a 3rd party provider that sells fully built 3 chain connectors for about $3.

[shanerooni]

is there a way to create an S-mapper with the adafruit hat? i'm willing to give it a shot and see how the display looks before venturing to a separate board.

[shanerooni]

sorry to be persistent, but is there a way to do this without the adapter if i'm okay with the low refresh rate? i just need to invert those middle 4 panels. thanks!