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https://github.com/doumanash/rpi_ws281x-sys

Rust bindings to rpi_ws281x
https://github.com/doumanash/rpi_ws281x-sys

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Rust bindings to rpi_ws281x

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README 

        
# rpi_ws281x-sys



![Rust](https://github.com/DoumanAsh/rpi_ws281x-sys/workflows/Rust/badge.svg?branch=master)

[![Crates.io](https://img.shields.io/crates/v/rpi_ws281x-sys.svg)](https://crates.io/crates/rpi_ws281x-sys)

[![Documentation](https://docs.rs/rpi_ws281x-sys/badge.svg)](https://docs.rs/crate/rpi_ws281x-sys/)



Bindings to [rpi_ws281x](https://github.com/jgarff/rpi_ws281x)



Sources from [1ba8e385708fb7802b09c0177a7ea4293948e25c](https://github.com/jgarff/rpi_ws281x/commit/1ba8e385708fb7802b09c0177a7ea4293948e25c)



### GPIO Usage:



The GPIOs that can be used are limited by the hardware of the Pi and will

vary based on the method used to drive them (PWM, PCM or SPI).

Beware that the GPIO numbers are not the same as the physical pin numbers

on the header.



PWM:

```

        PWM0, which can be set to use GPIOs 12, 18, 40, and 52.

        Only 12 (pin 32) and 18 (pin 12) are available on the B+/2B/3B



        PWM1 which can be set to use GPIOs 13, 19, 41, 45 and 53.

        Only 13 is available on the B+/2B/PiZero/3B, on pin 33

```



PCM:

```

        PCM_DOUT, which can be set to use GPIOs 21 and 31.

        Only 21 is available on the B+/2B/PiZero/3B, on pin 40.

```



SPI:

```

        SPI0-MOSI is available on GPIOs 10 and 38.

        Only GPIO 10 is available on all models.

        See also note for RPi 3 below.

```



### Power and voltage requirements



WS281X LEDs are generally driven at 5V. Depending on your actual

LED model and data line length you might be able to successfully drive

the data input with 3.3V. However in the general case you probably

want to use a level shifter to convert from the Raspberry Pi GPIO/PWM to 5V.



It is also possible to run the LEDs from a 3.3V - 3.6V power source, and

connect the GPIO directly at a cost of brightness, but this isn't

recommended.



Know what you're doing with the hardware and electricity. I take no responsibility for damage, harm, or mistakes.



### Important warning about DMA channels



You must make sure that the DMA channel you choose to use for the LEDs is not [already in use](https://www.raspberrypi.org/forums/viewtopic.php?p=609380#p609380) by the operating system.



For example, **using DMA channel 5 [will cause](https://github.com/jgarff/rpi_ws281x/issues/224) filesystem corruption** on the Raspberry Pi 3 Model B.



The default DMA channel (10) should be safe for the Raspberry Pi 3 Model B, but this may change in future software releases.



### Limitations:



#### PWM



Since this library and the onboard Raspberry Pi audio

both use the PWM, they cannot be used together.  You will need to

blacklist the Broadcom audio kernel module by creating a file

`/etc/modprobe.d/snd-blacklist.conf` with



    blacklist snd_bcm2835



If the audio device is still loading after blacklisting, you may also

need to comment it out in the /etc/modules file.



On headless systems you may also need to force audio through hdmi

Edit config.txt and add:



    hdmi_force_hotplug=1

    hdmi_force_edid_audio=1



A reboot is required for this change to take effect



Some distributions use audio by default, even if nothing is being played.

If audio is needed, you can use a USB audio device instead.



#### PCM



When using PCM you cannot use digital audio devices which use I2S since I2S

uses the PCM hardware, but you can use analog audio.



#### SPI



When using SPI the led string is the only device which can be connected to

the SPI bus. Both digital (I2S/PCM) and analog (PWM) audio can be used.



Many distributions have a maximum SPI transfer of 4096 bytes. This can be

changed in `/boot/cmdline.txt` by appending

```

    spidev.bufsiz=32768

```



On an RPi 3 you have to change the GPU core frequency to 250 MHz, otherwise

the SPI clock has the wrong frequency.



Do this by adding the following line to /boot/config.txt and reboot:



```

    core_freq=250

```



On an RPi 4 you must set a fixed frequency to avoid the idle CPU scaling changing the SPI frequency and breaking the ws281x timings:



Do this by adding the following lines to /boot/config.txt and reboot:



```

    core_freq=500

    core_freq_min=500

```



SPI requires you to be in the `gpio` group if you wish to control your LEDs without root.