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Thread: Some sparkly old pixels w/ AlphaPix16 controller - Compatibility? Timing issue?

  1. #1
    Join Date
    Oct 2012
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    Question Some sparkly old pixels w/ AlphaPix16 controller - Compatibility? Timing issue?

    I bought an AlphaPix16 3 years ago, It is is a v1 board and has the last firmware v1.11 21-July-2016.

    For 3 years now it has happily driven all my WS2812 strips. This year I added a tree with 300 brand new WS2811 pixels, and a fence with 300 WS2811 bullet pixels I've had for several years. (Those 12mm epoxy encased Chinese ones all over eBay and AliExpress in batches of 50, 3 wire, 5 volt) The 2812 strips still work fine. The tree with the new pixels works fine. The old pixels do not! At first I thought it was a cable problem, but after much swapping things around and testing and troubleshooting have eliminated that possibility, and I'm sure the pixels are good.

    Symptoms: The first several pixels work as expected, the next few get progressively flakier, and then from pixel 8-10 or so onward, they just "sparkle" in random colors. (It would be a cool effect if it was intentional and only did it when I wanted it to!)
    The 300 pixels are actually in 3 different interchangeable groups of 100 with matching connectors on both ends. (Which also allows for power injection).
    If I hook the 3 sections up directly to the AlphaPix they all 3 still do the same thing. They do it whenever they are receiving data, either sent over E1.31/DMX/LOR or when the AlphaPix is in it's built-in test modes.
    BUT they work fine with an Arduino and an ESP8266 based testers. They used to work with TinyPix controllers, but once I got the AlphaPix16 I gave the TinyPix's to my nephew and I no longer have them for testing.
    When plugged directly into the AlphaPix they are getting 5.05 volts measured at the first pixel. Even on their normal long cable, which has 12 GA power wires, they are getting 4.79 volts. Even at the end of the long cable (data pair is twisted AND shielded) the data signal looks pretty clean on the oscilloscope with square corners. It's a really cheap scope so I can't be too sure of the frequency but it does appear to be right around 800KHz/Kbps.
    Also, a friend of mine has some AlphaPix16 controllers and a ton of the very same pixels*, all bought at the same time as mine, and they work good for him. I plan to take mine over to his house for testing but he lives on the other side of town so I haven't made it over there yet. (*Well, the majority of his are 12V, but he has some 5V too)

    Soooo... Has anyone seen this before, and did you find a solution?
    Wizlights.com

  2. #2
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    Default Re: Some sparkly old pixels w/ AlphaPix16 controller - Compatibility? Timing issue?

    Hi, about a year ago World Semi the manufacturer of WS2811 and WS2812s (now you know what the WS stands for if you didn’t) issued a new data sheet for their products. This had a couple of differences but one was significant, the ‘reset’ which is sent at the end of the data stream was changed from a minimum of 50uS to a minimum of 280uS. This meant that all controllers (to my knowledge) needed a firmware upgrade to run pixels manufactured after (let’s say) December 2017. It looks as if you may have come across this issue. I’m not familiar with the AlphaPix or its firmware, some of the firmware upgrades for other controllers required the user to set the ‘reset’ time using a new option on the setup page.

    I’m sorry that’s not a definitive answer but hope it might point you in the right direction.

  3. #3
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    Default Re: Some sparkly old pixels w/ AlphaPix16 controller - Compatibility? Timing issue?

    Actually, as you describe it, that should cause the opposite problem. If the new longer reset was the problem, then my new pixels would not work but the old ones should. But my problem is that the new bullet pixels from 2018 work, but the controller from 2016 does not control the bullet pixels which are also from 2016, or maybe 2015, but the pixel strips from 2014 do work. Go figure.
    Wizlights.com

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