LED Strip Configuration
Detailed descriptions of the LED Strip Configuration dialog.
This documentation aims to explain all of the settings in the LED Strip Configuration dialog, so you can make the most use of them.
Strip Type
Selection
The type of strip you have connected, for a complete list see supported hardware
Number of LEDs
Number
I hope this one is obvious enough 🙂
Max Brightness
Percentage
The maximum brightness the strip should reach in any effect.
GPIO Pin
Number
Colour Correction Settings
Number
The correction values for the red, green and blue channels. If your LED strip has a strong red, or the green is too bright, you can balance it out using these settings. They are applied as percentages, the defaults are 100% on all channels.
Use dedicated white
Checkbox
Dedicated white LEDs on an RGBW strip will be used if the R, G, B values in an M150 command are equal, or a W is specified in the command.
Skip first LED
Checkbox
If enabled, all effects will start at the second LED. Useful if a single LED is being used to stabilise the signal to the rest of the strip.
Frequency
Number
Frequency to drive the LEDs at. This should be 800 000 in normal use, some older strips may require different values.
Invert Pin output
Checkbox
Invert the signal from the Raspberry Pi. Useful if your setup uses a level shifter that inverts the signal, it can be inverted again to make it the right way around in the end.
DMA Channel
Number
(Not available in the UI)
Do not change the DMA channel if you do not know what you are doing.
This should be 10 in normal use, other values can cause severe problems.
PWM Channel
Number
(Not available in the UI)
Internal PWM Channel. Irrelevant to the plugin since it uses SPI in most cases.
DMA Channel and PWM channel are only available for editing using config.yaml, just in case you need to change this. You probably won't.
GPIO Pin Options
What other pins work?
To run this without root access, you must use an SPI pin. WS281x LEDs require specific timing pulses, and not every pin can produce these.
On all Pi's, the default, GPIO 10 can be used.
On all Pi's except the original Pi 1 model A and Pi 1 model B, GPIO 20 can be used. This requires adding dtoverlay=spi1-3cs to the /boot/config.txt file to enable SPI1
Other SPI interfaces are available, specific to certain Raspberry Pi models. More details on them can be found on the Raspberry Pi Documentation which contains detailed information. It is unknown if they all work with WS281x LEDs.
Using GPIO 20 is untested, and may not work with the library correctly.
Can I use a PWM pin?
Using a PWM pin to drive WS281x LEDs on a Raspberry Pi requires root access. This is out of my control. It is not recommended to run OctoPrint (or any web server) with root privileges due to security reasons. So while yes, you can use PWM you are on your own to configure OctoPrint to run as root.
What about some other GPIO pin?
If it's not an SPI capable pin, or a PWM capable pin then no. This is a hardware limitation of the Raspberry Pi.
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