Author Topic: P4 for upclose window display  (Read 755 times)

Offline sklankowski

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P4 for upclose window display
« on: August 29, 2018, 11:20:15 AM »
Looking to create a in window display for upclose viewing.  Ray Wu has the P4 panels available (https://www.aliexpress.com/store/product/P4-indoor-3-in-1-LED-soft-flexible-display-unit-64-32-pixels-256mm-128mm-size/701799_32900999982.html?spm=2114.12010615.8148356.2.787e4f60ml1EP7 ) which I would use about 8 panels, I was wondering which BBB i should go for, black or or pocket for scan rate?

Offline pixelpuppy

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Re: P4 for upclose window display
« Reply #1 on: August 29, 2018, 11:30:59 AM »
They're FLEXIBLE!  Cool!  8)    But ouch .. that price  :-[
-Mark

Offline JonB256

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Re: P4 for upclose window display
« Reply #2 on: August 29, 2018, 12:35:31 PM »
BBB or BBG with an Octoscroller (my favorite for panels, unless you wanted to try Colorlight and RasPi3b+)

As far as price goes, that is the resolution of 4 P10 panels, so it is cheaper per pixel.

Offline pixelpuppy

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Re: P4 for upclose window display
« Reply #3 on: August 29, 2018, 01:38:55 PM »
As far as price goes, that is the resolution of 4 P10 panels, so it is cheaper per pixel.
I was comparing it to P5 panels which are the same resolution for less than half the price (yes I know this have a slightly tighter pitch)

Offline dkulp

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Re: P4 for upclose window display
« Reply #4 on: August 29, 2018, 01:56:26 PM »
Looking to create a in window display for upclose viewing.  Ray Wu has the P4 panels available (https://www.aliexpress.com/store/product/P4-indoor-3-in-1-LED-soft-flexible-display-unit-64-32-pixels-256mm-128mm-size/701799_32900999982.html?spm=2114.12010615.8148356.2.787e4f60ml1EP7 ) which I would use about 8 panels, I was wondering which BBB i should go for, black or or pocket for scan rate?


For 8 panels, you could put 1 panel per output on the OctoScroller and have slightly higher scan rate than the 2 panels per output that would be required for the PocketScroller.   However, 2 panels per output on the PocketScroller would not have any noticable flicker or anything anyway.  Thus, it really doesn't matter which way you go.




Offline pixelpuppy

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Re: P4 for upclose window display
« Reply #5 on: August 29, 2018, 02:41:21 PM »
For 8 panels, you could put 1 panel per output on the OctoScroller and have slightly higher scan rate than the 2 panels per output that would be required for the PocketScroller.   However, 2 panels per output on the PocketScroller would not have any noticable flicker or anything anyway.  Thus, it really doesn't matter which way you go.


Hmmm, this has me thinking.   I have a 4x4 P5 matrix on a BBB with Kulp-Octo-V2  8)


I currently have it wired 4 panels each on Outputs 1-4 with 5-8 unused.   I thought I read somewhere recently that you optimized the code so unused outputs would not use cycles (as long as the used outputs were contiguous).  Or in other words, that it can cycle faster though 4 outputs than through 8 outputs.  Did I get that wrong?   Is this one of those same-either-way scenarios, or is it always better to use the maximum outputs with the fewest panels each?

Offline dkulp

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Re: P4 for upclose window display
« Reply #6 on: August 29, 2018, 02:59:48 PM »
I currently have it wired 4 panels each on Outputs 1-4 with 5-8 unused.   I thought I read somewhere recently that you optimized the code so unused outputs would not use cycles (as long as the used outputs were contiguous).  Or in other words, that it can cycle faster though 4 outputs than through 8 outputs.  Did I get that wrong?   Is this one of those same-either-way scenarios, or is it always better to use the maximum outputs with the fewest panels each?


A longer "chain" is almost always worse than using an additional output.   Thus, it's always better to use more outputs with smaller chains.   The optimization you are talking about is to also not send data to the unused outputs, but they are in order.  THus, if you DON'T use all the outputs for whatever reason, make sure you use outputs starting from 1 and go up without skipping.   If you put 5 panels on output 8 and nothing else, it will be worse than if you put the 5 panels on just output 1.   However, it's still better to break it up and use 5 separate outputs.   


That said, 1 P10 panel per output will almost always trigger throttling.   One panel is too fast for the cheaper panels so I have to throttle things down a bit anyway.   


That all said, if you have it all wired up and you don't see any flickering, don't worry about it.   If it works, don't fix it.

Offline dkulp

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Re: P4 for upclose window display
« Reply #7 on: August 29, 2018, 03:08:10 PM »



If you want more "exact" information, you can check the timing matrices (in hex, clock cycles per row) at the top of:


https://github.com/FalconChristmas/fpp/blob/master/src/channeloutput/BBBMatrix.cpp


For P5, double the number of panels.   Thus, for your "v2" P5 panels, a 4x4 would take 0x53EB clock cycles where as flipping to an 8x2 would be 0x320D.  About 40% faster.

Offline pixelpuppy

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Re: P4 for upclose window display
« Reply #8 on: August 29, 2018, 03:31:25 PM »
For P5, double the number of panels.   Thus, for your "v2" P5 panels, a 4x4 would take 0x53EB clock cycles where as flipping to an 8x2 would be 0x320D.  About 40% faster.
Thanks for the detailed info...I'm a details kinda guy  ;D


A longer "chain" is almost always worse than using an additional output.   Thus, it's always better to use more outputs with smaller chains.   The optimization you are talking about is to also not send data to the unused outputs, but they are in order.  THus, if you DON'T use all the outputs for whatever reason, make sure you use outputs starting from 1 and go up without skipping.   If you put 5 panels on output 8 and nothing else, it will be worse than if you put the 5 panels on just output 1.   However, it's still better to break it up and use 5 separate outputs. 
That's what I suspected, but nice to hear it from "the man" himself  ;)


Quote
That all said, if you have it all wired up and you don't see any flickering, don't worry about it.   If it works, don't fix it.
I wish it were that easy.... there is that pesky little thing called OCD  :-[

Offline dkulp

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Re: P4 for upclose window display
« Reply #9 on: August 29, 2018, 04:20:00 PM »
One more note about the timings:  if the timing in the chart is under 0x4000, it won't matter as we'll increase it anyway.  The absolute minimum we'll output is 0x3500 as anything below that starts causing ghosting on some of the newer panels.   Thus, the 8x2 setup is not really 40% faster as it would get throttled down anyway.   

Offline pixelpuppy

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Re: P4 for upclose window display
« Reply #10 on: September 02, 2018, 10:05:47 PM »

Thus, the 8x2 setup is not really 40% faster as it would get throttled down anyway.   

Dan, since 8x2 is not really going to be 40% faster, then I'm back to wondering about this quote from your V2 Octo board announcement...
More optimized use of BBB GPIO bus - if using 5 or less outputs, the new wiring allow the PRU code to reduce the usage of GPIO bus in the BBB.  This results in less contention and about a 5-10% faster refresh on the panels.   If using 6 or more outputs, the refresh should be identical.
That makes me wonder if 4x4 would be better than 8x2 when using your v2 Octo board? 

Offline dkulp

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Re: P4 for upclose window display
« Reply #11 on: September 09, 2018, 07:28:22 AM »
More optimized use of BBB GPIO bus - if using 5 or less outputs, the new wiring allow the PRU code to reduce the usage of GPIO bus in the BBB.  This results in less contention and about a 5-10% faster refresh on the panels.   If using 6 or more outputs, the refresh should be identical.
That makes me wonder if 4x4 would be better than 8x2 when using your v2 Octo board?


No:  4x4 original:  0x6410
4x4 v2: 0x53EB
8x2: 0x320D




 

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