Author Topic: pixel limits for rpi 281x on board support  (Read 9971 times)

Offline gadgetsmith

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pixel limits for rpi 281x on board support
« on: March 03, 2016, 04:36:34 PM »
At the moment, i'm successfully driving 900 pixels (2700 channels) on a single output on a B+ at 25ms timing.  Going up to 1050 pixels, I start getting flickering.  Going to a 50ms timing file, I can run 1050 pixels (3150 channels) without an issue, so i'll need to add more channels to test further.

I thought i'd take a moment to report what I was getting, but i'm also interested in trying to get a good test fseq file to test with.  Something that will stress the lights to the limits.  Could this just be a quick fade up and down to full white?  If someone wants to make an fseq file, with about 5000 channels worth of data, starting at 1 and going to 5000, I can run it as a test.  Or if you just have an idea of an effect in xlights that will test the 281x library, please let me know what it would be, and I can create the fseq myself.

I'll be interested in how far I can go after initiating the second output!

I will be providing video of these test shortly.  :)



Offline CaptainMurdoch

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pixel limits for rpi 281x on board support
« Reply #1 on: March 03, 2016, 05:49:59 PM »
Wow, great numbers.  Sounds like we can easily change the current 400 pixel limit to 1000.

I think the butterfly would be a good test since it is constantly changing a lot of values.  It also will be easy to see if it stutters or jumps.  Make a large matrix model starting at channel 1 and that should be some good data.  Maybe throw in some all white and all black intermixed to see if the whole string changes at the same time.
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Chris

Offline mararunr

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Re: pixel limits for rpi 281x on board support
« Reply #2 on: March 04, 2016, 07:46:57 AM »
Wow....so you are increasing it to 1,000 pixels PER gpio and we can use 2 gpios, so effectively I could run my 32 x 50 megatree (1600 pixels) off a single Pi with FPP and no other controller...WOW!  Between this and the Bridge/AP point work going on, you all are really changing the game (again)!  Thank you so much.
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 This is just my opinion/suggestion/viewpoint.  Others with other viewpoints/experiences may have different advice.  I am a hobbyist with a couple years real world experience, not an expert.

Offline Aesl1982

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Re: pixel limits for rpi 281x on board support
« Reply #3 on: March 04, 2016, 08:12:30 AM »
I'm assuming This is with power injection?


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Offline russellmcfarland

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pixel limits for rpi 281x on board support
« Reply #4 on: March 04, 2016, 08:24:41 AM »
Yes.   The Pi is really only driving data.  You'd have to inject power with those counts on a string no matter which controller you are using.


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Offline JonB256

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Re: pixel limits for rpi 281x on board support
« Reply #5 on: March 04, 2016, 09:23:34 AM »
Slight topic hijack but relevant:

I have not tried driving pixels directly from a Pi (yet) but I have a question about the Data out from the GPIO port(s).

I understand that it will be 3.3vdc from the GPIO. Normal pixels expect 5.0vdc for data (Din).

Is the 3.3vdc going to be good enough to get to the first pixel (since that first pixel will then output 5vdc on Dout)?

Or should I use a uAmp as a level shifter to get it up to 5vdc immediately?

Offline gadgetsmith

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Re: pixel limits for rpi 281x on board support
« Reply #6 on: March 04, 2016, 10:37:59 AM »
Slight topic hijack but relevant:

I have not tried driving pixels directly from a Pi (yet) but I have a question about the Data out from the GPIO port(s).

I understand that it will be 3.3vdc from the GPIO. Normal pixels expect 5.0vdc for data (Din).

Is the 3.3vdc going to be good enough to get to the first pixel (since that first pixel will then output 5vdc on Dout)?

Or should I use a uAmp as a level shifter to get it up to 5vdc immediately?

See this thread about a pixel star I did for my Dad this past Christmas.

http://falconchristmas.com/forum/index.php/topic,3635.msg38806.html#msg38806

I used a buffer/line driver from RobG to get that distance, but a uAmp would surely do the same job. Buffer boards were only ~$1.50/ea

Offline gadgetsmith

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Re: pixel limits for rpi 281x on board support
« Reply #7 on: March 04, 2016, 10:42:57 AM »
Wow, great numbers.  Sounds like we can easily change the current 400 pixel limit to 1000.

I think the butterfly would be a good test since it is constantly changing a lot of values.  It also will be easy to see if it stutters or jumps.  Make a large matrix model starting at channel 1 and that should be some good data.  Maybe throw in some all white and all black intermixed to see if the whole string changes at the same time.

I think we're looking at more than that... and I haven't gotten to the v2 yet.  :)

I'm assuming This is with power injection?

Yes, most certainly power injection is required.

Offline CaptainMurdoch

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Re: pixel limits for rpi 281x on board support
« Reply #8 on: March 04, 2016, 10:53:12 AM »
I have not tried driving pixels directly from a Pi (yet) but I have a question about the Data out from the GPIO port(s).

I understand that it will be 3.3vdc from the GPIO. Normal pixels expect 5.0vdc for data (Din).

There are several solutions, you could use a uAmp, one of RobG's amp boards, or one of Ron's Pi Hat's which have the level shifter chip on the board.

Offline JonB256

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Re: pixel limits for rpi 281x on board support
« Reply #9 on: March 04, 2016, 10:58:43 AM »
Thanks to both. Since I have some uAmps I'll try them if it acts badly. Didn't order any of Ron's boards, though.
Ultimate goal will be to use a Pi Zero, but a Pi B+ will be fine. Now, if my WS2812b lights will get here from China. :(

Offline russellmcfarland

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Re: pixel limits for rpi 281x on board support
« Reply #10 on: March 04, 2016, 11:44:55 AM »
Has the code been updated where you can drive pixels from a Pi v2 yet?   I believe someone worked out a fix, but didn't know if it had been folded into the general FPP release.


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Offline DMJPixel

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Re: pixel limits for rpi 281x on board support
« Reply #11 on: March 04, 2016, 03:13:24 PM »
Has the code been updated where you can drive pixels from a Pi v2 yet?   I believe someone worked out a fix, but didn't know if it had been folded into the general FPP release.


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See this thread for info - works great:
http://falconchristmas.com/forum/index.php/topic,3709.msg45866.html#msg45866




Offline russellmcfarland

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Re: pixel limits for rpi 281x on board support
« Reply #12 on: March 04, 2016, 03:25:58 PM »
Excellent.  Thanks!


Offline DMJPixel

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Re: pixel limits for rpi 281x on board support
« Reply #13 on: March 04, 2016, 03:31:24 PM »
Sure - holler if it doesn't make sense or you have more questions.


Offline DMJPixel

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Re: pixel limits for rpi 281x on board support
« Reply #14 on: March 04, 2016, 03:34:59 PM »
Also, I have been messing with one of Ron's boards - here is a link to thread at another site; hope its OK to post...someone let me know if I should not link to other forums.


http://www.diychristmas.org/vb1/showthread.php?5358-PI-SPI-to-pixels-WS281x




 

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