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How to control Fixed Address NeoPixel LED Fairy Lights
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How to control Fixed Address NeoPixel LED Fairy Lights

by dnwklin on Wed Dec 01, 2021 1:23 am

I have a problem controlling https://www.adafruit.com/product/4917 the fixed address NeoPixel

I am using it with Arduino Uno and with this example code https://github.com/adafruit/Adafruit_Ne ... simple.ino

Suppose the line pixels.setPixelColor(i, pixels.Color(0, 150, 0)); will light up the LED from 0 to 99 where i is the address. However, whatever I do, it seem like the LED will just randomly light up and blink with random color. And it seems like only the first 7 or 8 LED will light up.

Any idea what I am doing wrong? I connect the red wire to +5v and black wire to ground in the power supply and the green wire to Arduino UNO.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by blnkjns on Wed Dec 01, 2021 4:31 am

The guide you link to pretty much explains the strange behaviour:
These look a lot like our NeoPixel fairy lights here, but have a funky twist. In fact, we're a little hesitant to call them NeoPixels because while they can be controlled by "NeoPixel" code, they don't function like NeoPixels. Technically, an NeoPixel is an LED that also acts as a shift register. 24 or 32 bits of brightness data comes in the input pin, and the LED removes it and passes along the rest. This is what lets folks chain as many pixels as they like onto the end: each pixel just grabs the first color data, and passes the rest down like a bucket brigade

These LEDs are not shift registers. In fact, if you look closely, there's no input and output pin, only one data line. That's because each LED in this strand is pre-addressed from 0 to 100. Whenever it receives the NeoPixel data, it picks out the n'th color data (matching to its pre-address) and displays that. You cannot change the pre-address, its fixed permanently - or at least, we have no idea how to re-address it.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by dnwklin on Wed Dec 01, 2021 2:57 pm

blnkjns wrote:The guide you link to pretty much explains the strange behaviour:
These look a lot like our NeoPixel fairy lights here, but have a funky twist. In fact, we're a little hesitant to call them NeoPixels because while they can be controlled by "NeoPixel" code, they don't function like NeoPixels. Technically, an NeoPixel is an LED that also acts as a shift register. 24 or 32 bits of brightness data comes in the input pin, and the LED removes it and passes along the rest. This is what lets folks chain as many pixels as they like onto the end: each pixel just grabs the first color data, and passes the rest down like a bucket brigade

These LEDs are not shift registers. In fact, if you look closely, there's no input and output pin, only one data line. That's because each LED in this strand is pre-addressed from 0 to 100. Whenever it receives the NeoPixel data, it picks out the n'th color data (matching to its pre-address) and displays that. You cannot change the pre-address, its fixed permanently - or at least, we have no idea how to re-address it.


It basically said each LED has a fixed address. So, if I send the signal to LED 0, the LED 0 should light up. If I send to LED 99, the 99 should light up.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by dnwklin on Sat Dec 04, 2021 2:24 pm

Anyone has any ideas on how to send commands using existing NeoPixel code? Or a different library to use?

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by adafruit_support_mike on Sun Dec 05, 2021 9:29 pm

They use the same control signals as regular NeoPixels.

The difference is that all the pixels listen to the data line at the same time. The Nth pixel knows how to select the Nth packet of color information it sees, and will ignore all the others. Regular NeoPixels pass information from one to the next, each consuming the first packet of color info it sees.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by dnwklin on Tue Dec 07, 2021 3:02 pm

adafruit_support_mike wrote:They use the same control signals as regular NeoPixels.

The difference is that all the pixels listen to the data line at the same time. The Nth pixel knows how to select the Nth packet of color information it sees, and will ignore all the others. Regular NeoPixels pass information from one to the next, each consuming the first packet of color info it sees.



Yeah, I understand the limitation on that. But I assume this sample NeoPixel code should work https://github.com/adafruit/Adafruit_Ne ... simple.ino
But it somehow only lights up the very first few LEDs. And the colors doesn't seem to match the what's set in the code. I did try adding a resistor between Arduino output and data line. No difference.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by blnkjns on Wed Dec 08, 2021 4:47 am

Do you think the RGB order is different. While initialising the NeoPixel library you can change the colour order. Default is GRB.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by dnwklin on Wed Dec 08, 2021 1:18 pm

blnkjns wrote:Do you think the RGB order is different. While initialising the NeoPixel library you can change the colour order. Default is GRB.


I have tried that. No difference. The color shows up on the LED just random and blinking while the code I use only specify one color. And also the command seems stop working after 16th-ish LED. The example code did default to 16 LED. I have change that number to 100

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by adafruit_support_mike on Wed Dec 08, 2021 8:30 pm

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

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Re: How to control Fixed Address NeoPixel LED Fairy Lights

by dnwklin on Thu Dec 09, 2021 4:27 pm

adafruit_support_mike wrote:Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.


I finally find out what's wrong with my setup. I'll post it here in case anyone else has the same problem.

You need to connect the ground wire from the LED to the GND in Arduino. Once it's connected, the LED is behaving what I expected.

Common Ground wire to Arduino is necessary.

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