NeoPixel RGB Neon-like on Raspberry Pi 3B+ won't light up Moderators: adafruit_support_bill, adafruit

[OleTR]

I'm currently having difficulties getting the NeoPixel RGB Neon-like from here to run on a Raspberry Pi 3B+

I have the 74AHCT125 connected to GPIO 18. This is powered by the 5V of the Pis GPIO.
The needed 12V are from an external power supply. The grounds are all connected.

When I set GPIO 18 to high, I get the needed 5V, so that part is working.

But when I connect the NeoPixel and run this simple code, nothing happens.

Code: Select all | TOGGLE FULL SIZE

import board
import neopixel

pixels = neopixel.NeoPixel(board.D18, 20) # Raspberry Pi wiring!

pixels[1] = (255, 0, 0)

I tried changing the pixel numbers to 19, but that also gave no results.

Is there something that I am missing?

[dastels]

Can you post clear photos that show your wiring and, more importantly, your connections?

Dave

[danhalbert]

I would also suggest that you try lighting a few NeoPixels with the same code, wired to a 3.3V pin and a 3.3V supply. That would remove the level shifter from consideration initially, and you could subdivide the problem.

[danhalbert]

Sorry, I mean without using the fancy 12V strip, if you have any regular NeoPixel strips. The 12V strip would not work in that wya.

[OleTR]

Here are some pictures of the wiring.
The two wires (red and blue) coming in are the 12V.
I hooked up a regular 5V 3000mA power supply to the Pi.

I checked with an oscilloscope and I get 5V data signals on the connector. I didn't check the timings, just if I get anything.
I tried with a 3.3V data signal, also no result.

Unfortunately I don't have any other NeoPixel at hand.

[dastels]

I agree with Dan: testing with a 5v NeoPixel product would simplify the situation.

Dave

[OleTR]

So I've gotten myself hold of a 5V LED stripe with WS2812.

I tried with the level shifter and directly to GPIO 18.

Nothing happens.

Is there anything I need to change on the pi interface options for it to run properly?

[danhalbert]

Try powering it with 3.3V (assuming it's not hugely long) and bypassing the level shifter. That will tell you whether there's a level-shifter problem or not.

[OleTR]

It's 60 LEDs, but I removed the fill command from my program, so I would only lit up like 3 LEDs, so it should be fine.
I could also go ahead and shorten the stripe if that is a problem.

I tried powering it with 3.3V, still nothing happens.

[danhalbert]

You could see if the 3.3V is sagging too much, but my guess is not. Make sure the strip is in the right direction (look at the arrows). If you are seeing NeoPixel signals on GPIO18, then it could be a timing issue or wiring.

[OleTR]

Arrows are in the right direction.
Like I mentioned previously, I do get data on pin 18, so it might be a timing issue.
Might there be any incompatibilites with the library and certain Raspberry OS versions?

[danhalbert]

What versions of everything are you using: OS, library, etc?

[OleTR]

Raspberry OS version is "Raspbian GNU/Linux 11 (bullseye)"

Python version is 3.9.2

For the libraries, if I run pip3 I get this:

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sudo pip3 install adafruit-circuitpython-neopixel
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Requirement already satisfied: adafruit-circuitpython-neopixel in /usr/local/lib/python3.9/dist-packages (6.3.0)
Requirement already satisfied: Adafruit-Blinka in /usr/local/lib/python3.9/dist-packages (from adafruit-circuitpython-neopixel) (7.3.0)
Requirement already satisfied: adafruit-circuitpython-pixelbuf in /usr/local/lib/python3.9/dist-packages (from adafruit-circuitpython-neopixel) (1.1.3)
Requirement already satisfied: Adafruit-PureIO>=1.1.7 in /usr/local/lib/python3.9/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (1.1.9)
Requirement already satisfied: adafruit-circuitpython-typing in /usr/local/lib/python3.9/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (1.6.0)
Requirement already satisfied: Adafruit-PlatformDetect>=3.13.0 in /usr/local/lib/python3.9/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (3.22.1)
Requirement already satisfied: rpi-ws281x>=4.0.0 in /usr/local/lib/python3.9/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (4.3.4)
Requirement already satisfied: pyftdi>=0.40.0 in /usr/local/lib/python3.9/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (0.54.0)
Requirement already satisfied: sysv-ipc>=1.1.0 in /usr/local/lib/python3.9/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (1.1.0)
Requirement already satisfied: RPi.GPIO in /usr/lib/python3/dist-packages (from Adafruit-Blinka->adafruit-circuitpython-neopixel) (0.7.0)
Requirement already satisfied: pyusb!=1.2.0,>=1.0.0 in /usr/local/lib/python3.9/dist-packages (from pyftdi>=0.40.0->Adafruit-Blinka->adafruit-circuitpython-neopixel) (1.2.1)
Requirement already satisfied: pyserial>=3.0 in /usr/lib/python3/dist-packages (from pyftdi>=0.40.0->Adafruit-Blinka->adafruit-circuitpython-neopixel) (3.5b0)
Requirement already satisfied: adafruit-circuitpython-busdevice in /usr/local/lib/python3.9/dist-packages (from adafruit-circuitpython-typing->Adafruit-Blinka->adafruit-circuitpython-neopixel) (5.1.8)


[jwinslade]

But when I connect the NeoPixel and run this simple code, nothing happens.

I've had trouble getting NeoPixels to work properly on the Pi 3 as well, and from what I can tell it's a low-level timing issue. Sometimes it seems to work, often it just remains dark.

Same code, similar pinout on the Feather will run fine. If you want a good sanity check, use a Feather or other Arduino type board to test the code.

[danhalbert]

I tried NeoPixels with the latest Bullseye on multiple RPi's.

I tried a simple example on a Pi 3B with the desktop running, and the NeoPixels did not work at all. Then I tried NeoPixels on a Pi 400 with desktop, and it worked.

But then I also installed the Lite version (no desktop), and tried it on a Pi Zero W and the same Pi 3B, and the NeoPixels worked.

So my guess is that the desktop is interfering with some aspect of the NeoPixel timing on slower Pi's. The Pi 4 is fast enough (or multiple-core enough) that it isn't an issue.