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Raspberry PI direct connect LED Pixel to GPIO 18?

Started by CyberMicha, December 21, 2021, 01:04:50 PM

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CyberMicha

Hi all,
i´ve read that it is possible to connect a pixel sting direct to the gpio 18 on the raspberry pi.

Is that wrong? I've tried it but the pixel stay dark when i start the sequenz.

See attached an image of the wiring an settings.

How do i have to setup xlights and flacon player? is there a tutorial for the actual version of falcon player?

kind regards
Michael

CyberMicha

Maybe i have to power up the voltage of the gpio 18? Using 12v Pixel but dont know the needed voltage of the data channel.

pixelpuppy

Quote from: CyberMicha on December 21, 2021, 02:24:03 PMUsing 12v Pixel but dont know the needed voltage of the data channel.
12v pixels use the same 5v data logic as 5v pixels.  Internally they're all 5v pixels.  The 12v pixel have voltage dropping resistors or a voltage regulator to drop the 12v supply voltage down to 5v into the ws2811 chip.   The data is the same for both.

Hard to tell from your picture but make sure you run Data AND Gnd from the GPIO's to the pixel.  Don't run just a data wire by itself.   It looks like you may have it wired right, but hard to see for sure.

More likely its not fully configured in the FPP software.  Post a screenshot of your FPP Channel Outputs -> Pixel Strings page so we can tell you if that's configured properly or not
-Mark

CyberMicha

#3
Hi Mark.
Thanks for your reply. I will post a Screenshot from fpp later.

The gpio 18 uses only 3.3v as far as i know. Problem?

An here´s the Screenshot of fpp

You cannot view this attachment.

pixelpuppy

Yeah, the GPIO is only 3.3v, but its not a problem as long as the distance to the first pixel is fairly close.

Looking at your screenshot shows the "Enable String Cape" check box is not enabled.  That's why nothing lights up.  You need to check that box and SAVE
-Mark

CyberMicha

Quote from: pixelpuppy on December 22, 2021, 06:10:56 AMYeah, the GPIO is only 3.3v, but its not a problem as long as the distance to the first pixel is fairly close.

Looking at your screenshot shows the "Enable String Cape" check box is not enabled.  That's why nothing lights up.  You need to check that box and SAVE
But i have no Cape? I will try later.


I got an answer from the seller of the string an he said that the 3.3v are under the minimun. Should be at least 4.5V.

Poporacer

Quote from: CyberMicha on December 22, 2021, 09:04:49 AMBut i have no Cape? I will try later.
Enabling the Cape is what sends the outputs to the GPIO pins, The capes are connected to those pins, so the cape has to be enabled to tell FPP to send the data to the GPIO pins.
If to err is human, I am more human than most people.

CyberMicha

So it is for now. Tomorrow i receive the logic level converter 3,3v to 5v. Hope it will work then. Don´t want to buy a expensive controller before i tried to control ws2811 pixel leds.

In xlights i will go for port 1 and 2.

pixelpuppy

Quote from: CyberMicha on December 22, 2021, 09:04:49 AMhe said that the 3.3v are under the minimun. Should be at least 4.5V.
It works.  Lots of people do it.  Especially with wearables like the hats you see with small scrolling pixel matrix.  I do it with a few Pi Zeros and pixels connected directly to the GPIO pins.
-Mark

CyberMicha

It´s dont working :(  I ve tested the voltage at gpio 18. It´s between 0.03 and 0.08v direkt at the gpio when i run a sequence.
What can i do :(

I think the output just dont work correctly.

CyberMicha

Again my Settings.


Maybe someone can post his settings with direct connected ws2811 leds?


Poporacer

Quote from: CyberMicha on December 23, 2021, 12:22:54 PMI ve tested the voltage at gpio 18. It´s between 0.03 and 0.08v direkt at the gpio when i run a sequence.
You can't test the Data with a multimeter, the Data is a fluctuation signal that goes from 0 to 3.3v and a multimeter will average the voltage, even on full white, the data signal is still going from 0 to 3.3V! The only real way to see the signal is with an oscilloscope.



Quote from: CyberMicha on December 23, 2021, 12:29:02 PMAgain my Settings.
Well, you do not have any pixels configured on your outputs, so you won't get anything out! Look at your pixel count.
If to err is human, I am more human than most people.

CyberMicha

Quote from: Poporacer on December 23, 2021, 01:26:18 PM
Quote from: CyberMicha on December 23, 2021, 12:22:54 PMI ve tested the voltage at gpio 18. It´s between 0.03 and 0.08v direkt at the gpio when i run a sequence.
You can't test the Data with a multimeter, the Data is a fluctuation signal that goes from 0 to 3.3v and a multimeter will average the voltage, even on full white, the data signal is still going from 0 to 3.3V! The only real way to see the signal is with an oscilloscope.



Quote from: CyberMicha on December 23, 2021, 12:29:02 PMAgain my Settings.
Well, you do not have any pixels configured on your outputs, so you won't get anything out! Look at your pixel count.
I also tried with 50 pixels on port 1 but nothing happens. Very frustated :/

Poporacer

Quote from: CyberMicha on December 23, 2021, 12:29:02 PMAgain my Settings.
You have some important items missing!

In xLights on your controller tab set your Vendor to FPP and Variant to Pi-Hat

Then set the Auto Layout Models and Full xLights control and Save
Then go to the Visualizer and assign the models to the ports you are using by dragging them in the correct place and exit and Save

Once you do that, then FPP Connect will work properly, make sure you put a check in the Cape option in the far right of the screen.
If to err is human, I am more human than most people.

Poporacer

Quote from: CyberMicha on December 23, 2021, 01:32:12 PMI also tried with 50 pixels on port 1 but nothing happens. Very frustated
You need to start at the controller. Test from the controller, if the lights are not lighting up using the test function in the controller itself, then it is usually a wiring problem, pixels wired on the wrong end, V+, Gnd, Data not properly connected to the correct pins, cable length too far for the voltage/Data, etc. 

Don't go any further if the testing from the controller isn't working first. You have to get it working there first.
If to err is human, I am more human than most people.

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