DMX2-24 - Interesting Flickering

Skymaster

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Thanks mate. Will dig in deeper and definitely let you know results. It's an interesting one for sure.
So further to this - the board came in whilst I was down in Melb earlier in the week, thank you Alan!

I have done some testing tonight and I can repeat the results. It certainly "feels" like it's a DMX decoding issue due to the way when the channels flip, the brightness carries across. i.e. if Ch3 is set to 128, and Ch4 is set to 0, they swap. Likewise if Ch3 is set to 255, when it swaps, it blinks to full brightness.

Data rate matters too. If I push 24 DMX channels of data down the line, it happens much more frequently than if I push the full 512ch universe down.

I am having LESS issues now using an ESP32 with ESPixelStick driving it compared to what I had with the Falcon and USB Dongle driving it, so there must be some timing discrepancies between them, not surprising I guess.
 

Kingfisher

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Interesting, I have two boards, one that I brought last year and one I got this year. I'll test them both and report the results.

Btw my set up involves the Enttec 70304 DMX USB Pro Dongle and Enttec 70303 USB dongle and run them both off a windows laptop using QLC+. I didn't have any issues last year with the one I had and being lazy I didn't use any termination on any of my dmx universes (yes I know I should) so I'll test it with and without termination and using both the internal and an external terminator.
 
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AAH

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Interesting, I have two boards, one that I brought last year and one I got this year. I'll test them both and report the results.

Btw my set up involves the Enttec 70304 DMX USB Pro Dongle and Enttec 70303 USB dongle and run them both off a windows laptop using QLC+. I didn't have any issues last year with the one I had and being lazy I didn't use any termination on any of my dmx universes (yes I know I should) so I'll test it with and without termination and using both the internal and an external terminator.
I have run a number of times without a termination over 100-200+m of dmx cat5 cabling and not had issues. I have had issues where I had mistakenly had to different boards terminated.


So further to this - the board came in whilst I was down in Melb earlier in the week, thank you Alan!

I have done some testing tonight and I can repeat the results. It certainly "feels" like it's a DMX decoding issue due to the way when the channels flip, the brightness carries across. i.e. if Ch3 is set to 128, and Ch4 is set to 0, they swap. Likewise if Ch3 is set to 255, when it swaps, it blinks to full brightness.

Data rate matters too. If I push 24 DMX channels of data down the line, it happens much more frequently than if I push the full 512ch universe down.

I am having LESS issues now using an ESP32 with ESPixelStick driving it compared to what I had with the Falcon and USB Dongle driving it, so there must be some timing discrepancies between them, not surprising I guess.
I haven't had time to hook an oscilloscope up to a boards to see if there is anything weird happening with the start bit detection which could potentially cause a 1 byte offset. I was also wondering if maybe there was an issue with me pumping out the dmx data from the Pic to the dimmer IC's having a timing clash of some sort. I am reasonably certain that it takes only a few milliseconds to pump out the data. While typing this I was wondering if maybe the start address that they are set to have any sort of effect on the issue. After my initial coding I probably never went back and tested with anything other than a start address of 1.
 

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While typing this I was wondering if maybe the start address that they are set to have any sort of effect on the issue. After my initial coding I probably never went back and tested with anything other than a start address of 1.
I had this suspicion as well, so I tried a start address of 65 and 257 with the same effect.

The off by 1 isn't quite right, it's a swapping of values. This might be between two frames, however, rather than the same frame.
It is reading channels 1-2-3-4-5-6-7-8, but outputting them as 1-2-4-3-5-6-8-7

My observations so far is that
* it's always the "even" pair of channels that's swapped, never the "odd" pair
* it is all outputs simultaneously, eg you'll never get just 7/8 swapping to 8/7, the others 3/4, 11/12, 15/16 all flip at the same time
* running the board in 12ch mode does not experience this issue
 

Kingfisher

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Ok so this is interesting...

I'm having a different issue, more of a glitch in my opinion.

I don't have any channels flipping around, instead all the even pairs have a glitch where at random times the second half will flash on.

I'm also seeing a flicker that appears to be the same speed as the data led on the boards.

Tested this with both the ENTTEC open DMX and PRO, running default settings using QLC+ on windows 11, same results. Nothing seemed to change regardless if I have the boards terminated or not.

The glitch I'm experiencing doesn't overly worry me as it's not noticeable with the way I program my display with everything always changing.

Here's a video of the glitch.

View: https://drive.google.com/file/d/1-SSU4C3XfjsbewpNm9JudDiZhdvG72sK/view?usp=drivesdk
 

Skymaster

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@Kingfisher - This is exactly the same behaviour I am seeing. The channels are "swapping" in this case - set half to 30%, and the other half to 100%, and you'll see that when this glitch appears, the brightness of the two strings are reversed.
 

Kingfisher

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@Skymaster

Ok, yeah I now understand what your saying, yeah it seems we are having the exact same issue and it's present on both of my 2-24 boards... now I'm wondering if it's also present on the 2-18s... I'll have to check that once I get them set up into a box and fix the 24v lights I use it for.
 

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Flickering fixed but broken other stuff in the process.
I found a couple of bugs that were in there since day dot. Still fixing the few things that I broke.
 
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