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Beta Sk6812 rgbw support

Discussion in 'Development' started by penfold42, 2 May 2016.

  1. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Is missing.

    I just bought some and will try to add support when they arrive.

    So.... RGB support is easy - we just send zeros for the white component.

    Any thoughts on how we should implement a 4 channel device ???
     
  2. Brindosch

    Brindosch Administrator Administrator

    Messages:
    585
    Hardware:
    RPi1/Zero, RPi2, RPi3, +nodeMCU/ESP8266
    A 4 channel chip, sounds interesting. You could mix up a white led with the rgb.
    Result maybe a better color?

    Puh, but how.
    Maybe @tvdzwan have an idea :)
     
  3. Rick164

    Rick164 Administrator Staff Member Administrator

    Messages:
    159
    Hardware:
    RPi2, +Arduino, +AtmoOrb
    One of the AtmoLight devs tried RGBW leds a while back however calibrating those things proved to be difficult and even FastLED support is lacking so driving those via an Arduino as a workaround with Hyperion would be hacky.
     
  4. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    My 2801 to 281x bridge should handle the 32 bit colours for those who want an arduino/atmega based adaptor.

    Guess I need to also provide rgbw support in hyperions 2801 driver too (which, is really just a raw SPI driver)

    I'll reuse this - http://codewelt.com/rgbw for the colour conversion.

    Looks like I'll need some more parameters - "rgbw transform" = ignore, warmwhite, coolwhite, naturalwhite
     
  5. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
  6. Brindosch

    Brindosch Administrator Administrator

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    585
    Hardware:
    RPi1/Zero, RPi2, RPi3, +nodeMCU/ESP8266
    Yeah great to hear that. But sadly no :(
     
  7. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
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  8. Alanwang

    Alanwang New Member

    Messages:
    1
    Hardware:
    +Arduino
    in fact you can use Arduino to control SK6812 LED RGBW chip , the thing you need to is write the 4 time channel as White ,
     
  9. penfold42

    penfold42 Moderator Developer

    Messages:
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    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    I've tested my fork and it works.

    I'm going to create a PR tonight
     
  10. Brindosch

    Brindosch Administrator Administrator

    Messages:
    585
    Hardware:
    RPi1/Zero, RPi2, RPi3, +nodeMCU/ESP8266
    Great! Sad that i don´t own them.
     
  11. penfold42

    penfold42 Moderator Developer

    Messages:
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    PR done
     
    • Like Like x 1
  12. thommy86

    thommy86 New Member

    Messages:
    27
    Hardware:
    RPi1/Zero, RPi2, RPi3, +Arduino, +PhilipsHue
    Is it possible to provide a SK6812rgbw example video? I wanted to exchange my ws2812b for some new apa102.. But now with this development I'm not sure anymore.
     
  13. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    I'll see what I can do on the weekend - I'm not sure it will show much difference tho.

    What don't you like about the 2812 ?
     
  14. Doc.Ex

    Doc.Ex Member

    Messages:
    72
    Hardware:
    RPi2, +PhilipsHue
    I am also interested with the potential difference.
    I currently use the lpd8806 and I am not quite satisfied with the performance and colour accuracy in dark scenes. Tried everything with calibration, but it seems the thresholds of the leds or the possible brightness steps aren't good enough. Maybe the APA102 would perform better because of the 8bit pwm resolution instead of 7-bit of the lpd8806.

    However, maybe the colour accuracy is better with rbgw anyway. This video is very promising:
     
  15. Brindosch

    Brindosch Administrator Administrator

    Messages:
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    i bought one. Waiting for delivery now. I may able to do a comparison of APA102 behind the TV and this one.
     
    • Like Like x 1
  16. Doc.Ex

    Doc.Ex Member

    Messages:
    72
    Hardware:
    RPi2, +PhilipsHue
    Nice, I am excited. How is the support implemented? Are the white leds only used for full white input or do they mix with the rgb colours to produce lighter colours?
     
  17. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    right now there are only 2 algorithms for calculating W. The code is in utils/RgbToRgbw.cpp
    white_off:
    W'=0, R'=R, G'=G, B'=B

    subtract_min:
    M=min(R,G,B)
    W'=M, R'=R-M, G'=G-M, B'=B-M

    There are problems with a simple subtraction (but it does work for now):

    • the light output isnt really linear (more like logarithmic) so simple subtraction isnt ideal
    • there are different variants of SK6812RGBW with different colour temperatures for the W component. We should use different algorithms to take this into account too.
     
    • Informative Informative x 2
  18. Doc.Ex

    Doc.Ex Member

    Messages:
    72
    Hardware:
    RPi2, +PhilipsHue
    Ah okay, yeah I figured it is not linear. Regarding the different variants, for ambilight purposes a rgbw stripe with neutral white (around 4000K) should always be used. Otherwise you would have to mix blue or red and green into it, which makes everything a lot more complicated. But yeah, I guess that people will buy ones with with warm white etc so maybe just consider them when implementing the support for rgbw.
     
  19. penfold42

    penfold42 Moderator Developer

    Messages:
    394
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Has anyone else tested this ?
     
  20. Brindosch

    Brindosch Administrator Administrator

    Messages:
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    Need to find some time, a 5 meter roll waits for testing :)