bad colors with Rpi2

[SylvainGirod]

Hi,

I'm trying to use NeoPixel Jewels with a raspberry pi 2 and raspbian. When I run the tests in the python/examples folder (strandtest.py), I don't get the colors that I should.

instead of red, I've got several colors, as blue, green, magenta, yellow etc) instead of green, I've got a simmilar output with darker colors instead of blue, nothing displays on the leds.

Do someone got that issue ?

[penfold42]

Which model do you have ?

It sounds like you have rgbw not RGB LEDs.

Check out the sk6812 branch. It adds support for rgbw devices

[SylvainGirod]

Hi,

I use the RGB model with integrated drivers (reference adafruit : 2226), so, it must be RGB leds.

Is that possible that the differences between the code and the output is because I have an IMU wired to my pi too ?

[penfold42]

What's an IMU ?

[SylvainGirod]

inertial measurement unit. I use it to detect the raspberry pi's position in the space (like a mobile phone can do to adjust its screen). I need to use it to start or stop the leds depending on the Rpi position

[Gadgetoid]

The pixel order of ws2812 RGB LEDs is GRB. You can see this on Page 5 of the datasheet linked from Adafruit's store page for the NeoPixel Jewel: https://cdn-shop.adafruit.com/datasheets/WS2812.pdf

Composition of 24bit data:
G7 G6 G5 G4 G3 G2 G1 G0 R7 R6 R5 R4 R3 R2 R1 R0 B7 B6 B5 B4 B3 B2 B1 B0

The Adafruit NeoPixel Python library explicitly sets this, like so:

ws.ws2811_channel_t_strip_type_set(self._channel, ws.WS2811_STRIP_GRB)

You probably need a line not dissimilar to the above in your code.

There are, in fact, a number of different pixel orders and types built into this library which you can see here:

https://github.com/jgarff/rpi_ws281x/blob/4f5d727222ef4e48608d43c51b3b932c0840813d/ws2811.h#L45-L64

[Jokelo]

I had a similar problem here.

I agree with @Gadgetoid above. It definitely seems like the the pixel order is incorrectly setup. From what I've seen, I don't believe you can change the strip type within the strandtest.py without doing some major altercations to the initialization statement. I'd recommend changing the strip type within the neopixels.py, and see if that works. You might have to use trial and error to find the right strip type.

If that doesn't work you can try using SK6812_strandtest.py and change the LED_STRIP (line 19) to the strip type of your LEDs and see if that works.

Hope this helps.

[jgarff]

You can simply change the strip type in the call to Adafruit_NeoPixel() in strandtest.py. All different strip types are supported. As for the strip type in your setup, there are several variants, so I believe the problem is simply that yours is different from the default. I've got several different types of strips, and I often have to use non-default settings.