teensy 3.1 and NeoPixel not working Moderators: adafruit_support_bill, adafruit

[briandw]

Hi,

I just got my NeoPixels and Teensy 3.1 board. It looked pretty simple to do with the OctoWS2811 lib. I got the Basic RGB LED Test for the lib loaded without difficulty. I wired pins 15 and 16 together hooked up the NeoPixel strip (just 10) with D1 on pin 2. I'm powering the whole thing from 3 D cells. When I plug it in the LEDs all flash then nothing. As far as I can tell everything should be fine but I don't see any blinking lights and I don't know where to start debuting this. Any suggestions would be much appreciated.

Brian

[adafruit_support_mike]

Post a photo of how you have everything connected and we'll take a look. The forum puts a limit on file sizes, but 800x600 tends to strike a nice balance between detail and size.

[briandw]

Thanks so much. Here is a quick snap. Please let me know if its good enough.

IMG_2415.JPG (175.12 KiB) Viewed 7554 times

[briandw]

As far as I can tell it should be this simple, but I must me missing something as I'm still stuck. You don't see the batteries, i have 3D cells coming in from the right. With all the talk about the difficult with power supplies I thought I would play it safe. I do see level shifters mentioned for the 3.3 to 5v issue, but on the teensy page they don't show them(I didn't see them) on that big video screen. Is a level shifter required?

Thanks again
Brian

[adafruit_support_mike]

Your connections look fine, and a 3-pack of D cells will make a fine power supply.

Post the code you're using and we'll take a look at that.

[pburgess]

Do you have a more 'vanilla' Arduino (e.g. Uno) to test with? That'd help distinguish whether it's a problem with the strip or the code. There've been some concerns that the timing values in the library are a bit out of whack.

[briandw]

Thanks for having a look. The code I'm using is the sample from the OctoWS2811 lib "led_display". I've also tried stripping that code down to just this:

#include <OctoWS2811.h>

const int ledsPerStrip = 10;

DMAMEM int displayMemory[ledsPerStrip*6];
int drawingMemory[ledsPerStrip*6];

const int config = WS2811_GRB | WS2811_800kHz;

OctoWS2811 leds(ledsPerStrip, displayMemory, drawingMemory, config);

void setup() {
leds.begin();
for (int i=0; i < ledsPerStrip; i++) {
leds.setPixel(i, 0xFF0000);
}

leds.show();
}


Thanks again.

[briandw]

Can I run these with a Adafruit Trinket ? The Trinket doesn't have enough storage for my needs but it would be a inexpensive way to test.

[pburgess]

Yeah, if you could try the basic strandtest sketch, that'd be great.

[briandw]

I ordered an Adafruit Trinket. I'll update when I get it.

[paulstoffregen]

Did you install Teensyduino 1.17 or 1.18-rc2? Updates were made in 1.18-rc1 and rc2 for Teensy 3.1, especially for the DMA-based OctoWS2811 library. If you installed 1.17, it probably would not work.

[paulstoffregen]

I tried this test just now, using 1.18-rc2, and I was able to reproduce the problem.

It turns out the latest WS2812B NeoPixels do require a 5 volt data signal. Older ones worked with 3.3V. Looks like the very newest ones do not.

Here it is with 3.3V signal directly from Teensy 3.1.

octo1.jpg (57.81 KiB) Viewed 7411 times

And here it is with the same signal converted to 5V using a 74HCT245 chip.

octo2.jpg (238.41 KiB) Viewed 7411 times

[paulstoffregen]

I have updated a OctoWS2811 page with a warning in red text and link to this thread.

I'm sorry you had to go through this frustrating experience. 3.3V signals have worked well for many WS2811/WS2812 LED strips. It seems they have changed recently. Hopefully that warning will save anyone else from this same problem.

[briandw]

Thanks for looking into this Paul. Sad that it's not working but glad that I'm not doing anything stupid :) I ordered the level shifter and I'll try again when I get it.

[pburgess]

Well that's cruddy news, and might impact some of the little Flora and Gemma projects.

Near as you can tell, does it have to be 5.0 Volts, or is the threshold voltage just a little bit higher than before? The datasheet claims Vdd * 0.7 (which would suggest 3.5V)...so really, technically, we were lucky to get away with this before...but it might be sufficient to lower the LED voltage to 4.5V (threshold is then 3.15V).

I've updated the NeoPixel Überguide to mention the level shifter. Thanks for the insights there.