Wrong colors on RGBW strip

[dbartelmus]

Hello, I've followed this tutorial https://www.instructables.com/id/ESP8266-HomeKit-NeoPixel-Light-Strip/ - and almost everything went smooth.
After flashing and getting strip to work there was issue of mixed up colours (each led have different colors) and wrong brightness on somecolors.
I'm using SK6812 RGBW - please help.

ps. is it possible to set custom amount of led or make/build bin file for it?

[AchimPieters]

@dbartelmus It's made for the WS2812 Integrated Light Source, so it's uses just Red, green and blue LEDs. The use for RGBW is on my todo list.

If you want to make you own start here: ESP HomeKit SDK – Full Installation

[rmuike]

@dbartelmus Use this https://github.com/maximkulkin/esp-homekit-demo/blob/master/examples/led_strip/led_strip.c and edit it so it fits your needs. That’s what I did.

[dbartelmus]

Thank you greatly. I will share my job later with you.

[dbartelmus]

This repository seems to support SK6812 through i2s - https://github.com/esp8266-setup/ws2812_i2s and I can see that author is using different bit patterns depending of led strand:

#if LED_TYPE == LED_TYPE_WS2812
const IRAM_DATA int16_t bitpatterns[16] = {
    0b1000100010001000, 0b1000100010001110, 0b1000100011101000, 0b1000100011101110,
    0b1000111010001000, 0b1000111010001110, 0b1000111011101000, 0b1000111011101110,
    0b1110100010001000, 0b1110100010001110, 0b1110100011101000, 0b1110100011101110,
    0b1110111010001000, 0b1110111010001110, 0b1110111011101000, 0b1110111011101110,
};
#endif

#if LED_TYPE == LED_TYPE_SK6812
static const uint16_t bitpatterns[16] = {
    0b1000100010001000, 0b1000100010001100, 0b1000100011001000, 0b1000100011001100,
    0b1000110010001000, 0b1000110010001100, 0b1000110011001000, 0b1000110011001100,
    0b1100100010001000, 0b1100100010001100, 0b1100100011001000, 0b1100100011001100,
    0b1100110010001000, 0b1100110010001100, 0b1100110011001000, 0b1100110011001100,
};
#endif

and code for ws2812_i2c that was linked above by @rmuike is from different source - it seems that this one is striped only for ws2812 strand - but I can be wrong.
On the other hand there is a function named hsi2rgb:
static void **hsi2rgb**(float h, float s, float i, ws2812_pixel_t* rgb)
and it's easy to find related one to RGBW hsi2rgbw - I'm curious if this as simple as this @rmuike?

[Kristian8606]

I would like to contribute to your example.
I added an on / off and reset button as well as a smooth color change and brightness.
https://github.com/Kristian8606/LED_Strip/blob/master/main.c

[AchimPieters]

@Kristian8606 Thank you for your contribution! I will have a look as soon as possible!

[AchimPieters]

very interesting! am curious how you would tackle RGBW?

[dbartelmus]

I've tried to make approach for "W" (RGBW) of @Kristian8606 code customisation but without success

[Kristian8606]

The only LED strip I have is ws2812b which is rgb and does not support W.
I think the one that supports rgbw is sk6812, but I don't have one.

[AchimPieters]

Okay, that's a pity, but how would you approach it?

[Kristian8606]

change this ws2812_i2s_init(LED_COUNT, PIXEL_RGBW); and this ws2812_i2s_update(pixels, PIXEL_RGBW); int r, g, b, w;

w = LED_RGB_SCALE * i * (1 -s);
rgb->red = (uint8_t) r;
rgb->green = (uint8_t) g;
rgb->blue = (uint8_t) b;
rgb->white= (uint8_t) w;

Someone to try will this work for sk6812?

[dbartelmus]

I've tried this, the real deal with HomeKit is to separate RGB and White cold/White warm channel, not to mix it like the HSI to RGB method to with this code to emulate white with all colors.
This code seems to have some references for white channel, look at every commented section like: // convert HSI to RGBW and etc.
I've done all of this but even RGB is flickering some random color not to mention that I don't get separate white channel like this: