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سؤال: Is there a technical data-sheet for the cjmc-2812-16?

السؤال بواسطة gregnier على 2018-07-04 03:25:41

BG344213471 You want to look up the datasheet for "WS2812 5050". The LEDs used are WS2812 5050. The 5050 refers to the size of the LED (5.0mm × 5.0mm). There are also 2020 models (2.0mm × 2.0mm) and the newer B-model, WS2812B. The different models seem to have different timings, but they have a fair amount of timing tolerance and the protocol is the same. Some small adjustments should make your code work on all these models. Just note that some timings are in the 300 ns range. That's 4 clock cycles on a 16MHz AVR (like the ATmega328P found on Arduino Nano). Probably wise to disable interrupts during data transfer. Check the assembly output and count clock cycles or use a logic analyser (the cheap LA 1001 is a must have unless you already have a better one). In your bit pushing loop you either don't need any delays or a few no-op's (1 cycle doing nothing = 62.5 ns delay) for the longer delays.

2022-12-21 08:10:39 مساعدة (1)
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BG344213471 I found them rather easy to program but you definitely have a point thought because there are some variations of these LEDs that looks identical at a first glance but they've got slightly different timings and they're kind of tight on your average MCU so make sure you get the right datasheet. They're so-so but for an engrish datasheet and the simplicity of the protocol they're good enough, if they bother to actually mention which model it applies to. Having read through the timings for different models there is a common timing scheme that seems to work on most devices. The reset time varies and is not very accurate in regards to actual use (they might say 50 ms when 8 ms is plenty, or maybe it was micros but regardless... it's a bit of trial and error of you're writing your own code but it's not that time consuming, just a few tweaks here and there and they'll happily cause temporary blindness if you're not aware of how bright these things can be).

DrMichael 12/08/2022
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BG344213471 Thanks for the detailed review. I've 50 of these on the way for a project or two. I have the 64 (8x8) WS2812B 5050 matrix, wrote my own AVR code for it to make work because I wanted to (surprisingly easy to program) and my burned eyebrows confirms that my code is indeed working. Man these things are bright! Question. Do these things get dimmer at 3.3V vs 5V? I can't really tell the difference in brightness after about 50% (128,128,128) and (255,255,255) appear pretty similar. The other thing is gamma, but I'm guessing at least Adafruit has some features to handle this. Do you use gamma tables for more accurate color mixing? One table for each primary or one common table (sacrifices some accuracy given how green is a lot brighter than the other two, and there's also a difference between red and blue but not as extreme). Do you use the whole range or reduce it to a predefined gamma corrected 16 or 256 color palette? I mean if you've played around with it to that extent that is. I guess most people just want it to work and use existing libraries to get things going, but since I'm a curious idiot I run into things like this so ... any feedback from you or anyone else always appreciated. Thanks! Have fun!

Neo2121 02/06/2016
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سؤال: does this come with a users manual?

السؤال بواسطة james على 2017-11-13 12:13:08

BG344213471 Depends on what you mean by "users manual". The datasheet for the MAX7219 controller is excellent and all you need to know to program these things. If you want plug and play there are multiple libraries to choose from.

2022-08-31 02:16:09 مساعدة (0)
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سؤال: Can I daisy chain several of these? By just connecting output of the first with input of the next?

السؤال بواسطة halvorkise على 2019-07-26 02:27:41

BG344213471 Yes. Remember, there are already 4 of these ICs chained together. The PCB comes with connections for further chaining, but as mentioned you probably need to inject some extra power.

2022-08-31 02:13:36 مساعدة (0)
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سؤال: what colors are possible?

السؤال بواسطة KATOK على 2017-12-25 10:43:26

BG344213471 @BG495298131 look it up in the MAX7219 datasheet. Another cool thing about these ICs is the need for just one resistor to limit the current for all segments x digits (64 per IC) to retain the same brightness whether only one LED is on or all 64. IIRC there's a chart there with recommended resistor values depending on number of LEDs. I could probably lift one of the 8x8 matrices off and see what resistor value they've used, but the datasheet should give you an idea. Assume you need an external power supply though. They're not super bright but it's still 256 LEDs.

2022-08-31 02:08:01 مساعدة (0)
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