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Controlling WS2812 device on Omega2 board



  • Re: Controlling WS2812 device (RGB LED strip)

    I have ported the above mentioned ws2812 driver in to latest SDK running kernel 4.14.
    Driver source: https://github.com/jnweiger/ws2812_sprites/tree/master/carambola2/package/ws2812_draiveris/src
    I haven't modified anything in the driver except #include <asm/uaccess.h> to #inlclude <linux/uaccess.h> as the asm/uaccess.h was throwing error of incompatibility.

    After compiling it successfully for omega2, i am able to insert it successfully via insmod, the dmesg shows appropriate logs as well.
    But when I try to write to glow LEDs(echo "}!!!}!!!}" > /dev/ws2812) it does not show any effect on the specified GPIO pin.

    I am using GPIO 18 and my LED has 5 leds in it; I am following below sequence,
    insmod ws2812_driveris.ko gpios=18 leds_per_gpio=5
    echo "}!!!}!!!}" > /dev/ws2812

    This does not have any effect on LEDs, LEDs are in Off state.

    I am suspecting that the low level GPIO registers which are being written/read in the driver are not for Omega2.
    Help me to understand this better!

    Thanks in advance.



  • However I am able to access the GPIO 18 with sysfs interface, to make it hgh-low.



  • Hi @dixit,

    the ws2812_draiveris driver is for the AR9331 SoC. This was used in the first Omega(1), that's what we've had at the time, and that's what I ported ws2812_draiveris for back in 2016.

    Today's Omega2 family however are all based on MediaTek's MT7688 SoC, which is quite different hardware. So you ws2812_draiveris will never work on a Omega2.

    But no worries - a much better solution than ws2812_draiveris exists since 2017 for the Omega2, and has in fact become part of the official firmware - p44-ledchain. It uses MT7688 PWM to generate the WS281x data without blocking IRQs. See this thread for the history how it came into existence.

    The p44-ledchain README explains how to use it, and there are also a few other threads in this forum with some Q&A about WS281x and p44-ledchain.

    happy LED hacking šŸ˜‰



  • @luz I got it from there only, Thanks.



  • p44-lechain is amaaaaazing! Makes using LEDs really easy. Thank you @luz



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