Addressable LEDs are beginning to supersede RGB LEDs for their flexibility and relative ease of use. With each individual element capable of displaying an entire spectrum of colors at very high speed, they can be used to create a variety of lighting effects.
At this time, Klipper supports most WS2812 compatible (Neopixels) and APA102 compatible (Dotstar) chips for LED Effects.
Neopixel type LEDs require one digital IO pin and a supply of power. Most are 5V but can be driven from a 3V source. Check manufacturer specifications to ensure they will work with your board. Each individual emitter has 4 pins. VCC, GND, Din, and Dout. Neopixel strips typically have 3 solder pads or a connector with 3 pins and arrows indicating the direction of the data. The D pins are unidirectional and cannot be reversed. When attaching them to your printer, the Din or D→ connection should be attached to an available digital IO pin on the MCU board. The VCC connection is attached to a supply voltages that is compatible with the LED strip. Neopixels will typically use 60mA of current per emitter at full brightness so depending on the power capabilities of your printer board, it is recommended that they be powered from a separate power source. It is important that a GND wire be run from the Neopixel chain back to the MCU board in addition to the GND to the power source. This will ensure the board can communicate with the strips.
The number of discrete emitters per IO pin is limited. It is possible to wire two strips to the same data pin and have them show the same colors. It is also possible to specify multiple LED chains on different IO pins in the LED Effects configuration settings.
APA102 Dotstar LEDs are similar to the Neopixel LEDs with the exception that Dotstar uses one-way SPI for communication. This requires the addition of a clock signal for the emitters. Multiple strips should be able to share the same clock pin but they each require their own data line.
In your config file, each strip or chain connected to an IO pin must have a definition. Each strips data pin (and clock pin if applicable) is defined along with the number of LEDs in the chain. The LED Effect instances are capable of using multiple strips of different types and color orders concurrently, but each strip must first be defined by its type.
[neopixel panel_ring]
pin: ar6
chain_count: 16
Effects are, in a more abstract sense, a state that the strips exist in. Effects can be comprised of 1 led or 100. There can be one effect layer or 10. It is all arbitrary and extensible. This means the only limit to how many layers and LEDs can be run concurrently is how much processing power the host OS is capable of handling. During initial testing, upwards of 100 LEDs and 12 effect layers were run concurrently on a Raspberry Pi 4 at 24 FPS.
For our example printer, there is one Neopixel ring with 16 LEDs that is situated on the front panel, and a short segment of Neopixel LEDs next to the hot end for illuminating the print.
There are also 5 Dotstar LEDs located underneath the bed. Pin numbers listed here are completely made-up.
[neopixel panel_ring]
pin: ar6
chain_count: 16
[neopixel tool_lights]
pin: ar15
chain_count: 6
[neopixel bed_lights]
data_pin: ar21
clock_pin ar22
chain_count: 5
We would like the ring to turn on a light shade of blue when the printer comes online, and we want the brightness to breathe in and out.
[led_effect panel_idle]
autostart: true
frame_rate: 24
leds:
neopixel:panel_ring
layers:
breathing 10 1 top (.5,.5,1)
This has defined an effect called panel_idle that can be controlled
via the gcode command SET_LED_EFFECT EFFECT=panel_idle. Calling the command
enables this effect. It can be disabled again by calling
SET_LED_EFFECT EFFECT=panel_idle STOP=1. Running STOP_LED_EFFECTS disables
all active effects.
autostart: true Setting this to true frame_rate
run_on_error
heater
analog_pin
stepper
The leds: section is a list of Neopixel or Dotstar strips that will
make up the effect. Both types can be used for the same effect. Each
strip is defined on a separate line and indented beneath the leds:
section.
leds:
neopixel:panel_ring
neopixel:tool_lights
dotstar:bed_lights
Additionally, one may decide to only have certain LEDs displaying the effect. This is accomplished by providing the index of the LEDs to be used after the strip name. The index can be a list or a range. If the indices are omitted, the entire strip is used.
As well, if for some reason you needed to, the same strip can be used twice in an effect with different emitters being specified.
leds:
neopixel:tool_lights
neopixel:panel_ring (1-7)
neopixel:panel_ring (9-16)
dotstar:bed_lights (1,3,5)
Effects are generated as frames. Each frame contains the number of pixels equal to the number of LEDs defined for the effect. So an effect with 22 LEDs specified would have 22 pixels per frame.
Each effect layer is generated as a frame. Each layer frame is blended with the next to generate the effect. Blending is cumulative and how colors are blended is defined by the blending mode of the top layer. Each effect layer is listed on its own line and each has its own settings.
Most effect layers such as breathing and gradient are pre-rendered when Klipper starts in order to save on computing them later. Others such as Fire and Twinkle are rendered on demand.
Each layer is defined with the following parameters
- Layer name
- Effect Rate
- Cutoff
- Blending mode
- Color palette
Each layer must be on a single line and each line must be indented. Color palettes can be of unlimited length but may be compressed depending on the size of the frame or number of LEDs on a strip. Colors are defined as groups of Red, Green, and Blue. The range for each color is a decimal number from 0.0 to 1.0. So for yellow, you would use ( 1.0, 1.0, 0.0 ).
Individual colors should be wrapped in parentheses and separated by commas.
Some Sample Palettes:
Rainbow (1.0, 0.0, 0.0),(0.0, 1.0, 0.0),(0.0, 0.0, 1.0)
Fire (0.0, 0.0, 0.0),(1.0, 0.0, 0.0),(1.0, 1.0, 0.0),(1.0, 1.0, 1.0)
Blue Comet (0.8, 1.0, 1.0),(0.0, 0.8, 1.0),(0.0, 0.0, 1.0)
layers:
breathing .5 screen (0,.1,1), (0,1,.5), (0, 1,1), (0,.1,.5)
static 1 bottom (1,.1,0), (1,.1,0), (1,.1,0), (1,1,0)
There are several effects to choose from.
Effect Rate: Not used but must be provided
Cutoff: Not used but must be provided
Palette: Colors are blended evenly across the strip
A single color is displayed and it does not change. If a palette of multiple colors is provided, colors will be evenly blended along the LEDs based on difference in hue.
Effect Rate: 3 Duration of a complete cycle
Cutoff: 0 Not used but must be provided
Palette: Colors are cycled in order
Colors fade in and out. If a palette of multiple colors is provided, it will cycle through those colors in the order they are specified in the palette. The effect speed parameter controls how long it takes to "breathe" one time.
Effect Rate: 1 Duration of a complete cycle
Cutoff: 0 Not used but must be provided
Palette: Colors are cycled in order
LEDs are turned fully on and fully off based on the effect speed. If a palette of multiple colors is provided, it will cycle through those colors in order.
Effect Rate: 1 Number of times per second to strobe
Cutoff: 1.5 Determines decay rate. A higher number yields quicker decay
Palette: Colors are cycled in order
LEDs are turned fully on and then faded out over time with a decay. If a palette of multiple colors is provided, it will cycle through those colors in order. The effect rate controls how many times per second the lights will strobe. The cutoff parameter controls the decay rate. A good decay rate is 1.5.
Effect Rate: 1 Increases the probability that an LED will illuminate.
Cutoff: .25 Determines decay rate. A higher number yields quicker decay
Palette: Random color chosen
Random flashes of light with decay along a strip. If a palette is specified, a random color is chosen from the palette.
Effect Rate: 1 How fast to cycle through the gradient
Cutoff: 0 Not used but must be provided
Palette: Linear gradient with even spacing.
Colors from the palette are blended into a linear gradient across the length of the strip. The effect rate parameter controls the speed at which the colors are cycled through. A negative value for the effect rate changes the direction the gradient cycles (right to left vs left to right)
Effect Rate: 1 How fast the comet moves, negative values change direction
Cutoff: 1 Length of tail (somewhat arbitrary)
Palette: Color of "head" and gradient of "tail"
A light moves through the LEDs with a decay trail. Direction can be controlled by using a negative effect rate value. The palette colors determine the color of the comet and the tail. The first color of the palette defines the color of the "head" of the comet and the remaining colors are blended into the "tail"
Effect Rate: 1 How fast the comet moves, negative values change direction
Cutoff: 1 Length of tail (somewhat arbitrary)
Palette: Color of "head" and gradient of "tail"
Identical settings as Comet, but with multiple lights chasing each other.
Effect Rate: 1 Minimum temperature to activate effect
Cutoff: 0 Disable effect once temp is reached
Palette: Color values to blend from Cold to Hot
This effect becomes active when the specified heater is active or the temperature is greater than the minimum specified temperature. For instance, if a heater is turned on and set to a target temperature, the LEDs will cycle through the gradient colors until the target temperature is met. Once it has been met, the last color of the gradient is used and the effect is essentially a static color until the Heater state changes. If the cutoff parameter is supplied, the effect will be disabled once the target temperature is met. If the heater is turned off, the colors will follow this pattern in reverse until the temperature falls below the minimum temperature specified in the config. This can be used to indicate the hotend or bed is in a safe state to touch.
Effect Rate: 45 Probability of "sparking"
Cutoff: 40 Rate of "cooling"
Palette: Color values to blend from "Cold" to "Hot"
The FastLED library for Arduino has a sample sketch called Fire2012WithPalette included with it. This effect is a port of that sketch. It simulates a flame by "sparking" an LED. The "heat" from that LED travels down the length of the LEDs where it gradually cools. A higher rate of sparking causes a greater amount of heat to accumulate at the base of the strip resulting a more intense flame. Changing the rate of cooling results in longer or shorter overall flames.
Effect Rate: 1 Minimum temperature to activate effect
Cutoff: 0 Disable effect once temp is reached
Palette: Color values to blend from "Cold" to "Hot"
The fire effect but responsive to the temperature of the specified heater. The flame starts as a small ember and increases in intensity as the heater's target temperature is reached. If the cutoff parameter is set to 1, the effect will be disabled once the target temperature is reached, otherwise it will stay active until the heater is disabled.
Effect Rate: 10 Multiplier for input signal
Cutoff: 40 Minimum threshold to trigger effect
Palette: Color values to blend
This effect uses the value read from an analog pin to determine the color. If multiple colors are specified in the palette, it chooses one based on the value of the pin. If only one color is specified, the brightness is proportional to the pin value. An example usage would be attaching an analog potentiometer that controls the brightness of an LED strip. Internally, input voltage is measured as a percentage of voltage vs aref. Another use could be to attach the RPM wire from a fan if the fan has a tachometer. It must be used with care as too much current or too high a voltage can damage a pin or destroy a controller board.
Effect Rate: 4 Number of trailing LEDs
Cutoff: 4 Number of leading LEDs
Palette: Color values to blend
The position of the specified stepper motor is represented by the first color in the palette. The remaining colors in the gradient are blended and mirrored on either side. As the stepper position changes relative to the axis length, the lights move up and down the strip. It should be noted that the effect itself updates stepper position every half second based on the reported position of the stepper similar to the GET_POSITION gcode command. It will not be realtime. A negative value in effect rate will fill the entire strip leading up to the stepper position, a negative value in cutoff will fill the entire strip after the stepper position.
Effect Rate: 4 Number of trailing LEDs
Cutoff: 4 Number of leading LEDs
Palette: Color values to blend
Exact same configuration as Stepper but instead of reporting stepper position, this layer reports print progress.
If you have ever used image editing software you may be familiar with color blending between image layers. Several common color blending techniques have been added to blend LED layers together. Layers defined in the configuration are ordered top to bottom.
If there are 3 layers defined, the bottom layer is first blended with the middle layer. The resultant layer is then blended with the top. The bottom layer will never be blended with anything even if a blending mode is specified.
Layer blending is always evaluated from the bottom up.
Since values cannot exceed 100% brightness and 0% darkness, they are clamped to this range as a floating-point number ( 0.0 - 1.0 )
No blending is done, the value from the color channel of the bottom layer is used.
No blending is done, the value from the color channel of the top layer is used.
( t + b )
Color channels (Red, Green, and Blue) are added to one another. This results in channels becoming brighter.
( t - b )
The the bottom layer is subtracted from the top layer. This results in darkening similar colors.
( t - b ) or ( b - t )
The darker of the layers is subtracted from the brighter of the two
( t + b ) / 2
The average of the channels is taken
( t * b )
The channels are multiplied together, this is useful to darken colors
( t / b )
The channels are divided, this results in brightening colors, often to white
1 - ( 1 - t ) * ( 1 - b )
The values are inverted, multiplied, and then inverted again. Similar to divide, it results in brighter colors
( t if t > b else b )
The brighter of the color channels is used
( t if t < b else b )
The opposite of lighten, the darker of color channels is used
( 2ab if a > .5 else 1 - 2( 1 - a )( 1 - b ) )
Overlay is a combination of multiply and screen. This has a similar effect of increasing contrast.
In the event of critical error, all LED strips breath red in unison to provide a visible indicator of an error condition with the printer. This effect is disabled during normal operation and only starts when the MCU enters a shutdown state.
[led_effect critical_error]
leds:
neopixel:tool_lights
neopixel:bed_lights
layers:
strobe 1 1.5 add (1.0, 1.0, 1.0)
breathing 2 0 difference (0.95, 0.0, 0.0)
static 1 0 top (1.0, 0.0, 0.0)
autostart: false
frame_rate: 24
run_on_error: true
[led_effect bed_effects]
leds:
neopixel:bed_lights
autostart: true
frame_rate: 24
heater: heater_bed
layers:
heater 50 0 add (1,1,0),(1,0,0)
static 0 0 top (1,0,0)
This is an example of how to combine the Analog Pin effect with layer blending so it controls the brightness of the lights. One could connect a potentiometer to a thermistor port and use the voltage reading from that pin to determine the amount of color to subtract from the base layers. The potentiometer would need to be wired so that when it is turned "down" the voltage on the analog pin is on full output and when it is turned up it is on minimum output. This way, when the potentiometer is "down", the color (1.0, 1.0, 1.0) (Full white) is being subtracted from the colors of the layer, resulting in (0.0, 0.0, 0.0) (Full Black). The effect rate and cutoff would need to be tuned to the specific potentiometer and board combination.
[led_effect bed_effects]
leds:
neopixel:bed_lights
autostart: true
frame_rate: 24
analog_pin: ar52
layers:
analogpin 10 0 subtract (1,1,1)
static 0 0 top (1,1,1)
Using a single strip of LEDs, print progress is displayed as a light blue line over a dark blue background
[led_effect progress_bar]
leds:
neopixel:progress_lights
autostart: true
frame_rate: 24
analog_pin: ar52
layers:
progress -1 0 add ( 0, 0, 1),( 0, 0.1, 0.6)
static 0 0 top ( 0, 0, 0.1)
This is usually due to some sort of signal issue. Most addressable LEDs have a specific protocol they use for communication. It typically involves sending bits of data at a specific interval followed by a reset latch to signal them to light up. They will stay the last color they were set until told to do something different.
With most implementations of addressable LEDs in printer firmware, the color data is sent once when the gcode command is executed and not sent again. As long as that initial signal is read, they will stay that color.
With this particular implementation, the color data is being updated at regular intervals determined by the effect frame rate. So 10 frames per second would result in 10 color updates to the LEDs per second.
The data lines are susceptible to electromagnetic interference from other electronics on the printer. When this interference is present, it can result in malformed data going to the LEDs.
To mitigate this, one can try insulating or isolating the data line from other wires. Try to keep the data lines as short as possible. This is especially problematic for 32 bit boards which typically output the data signal at 3.3V.
Signal integrity can also be deteriorated by ringing and reflections on the data line. Especially, when the cable to the first LED is rather long. This can be reduced by adding a 700 Ohm resistor in line to the data line directly in front of the first LED.
Another source of flickering is voltage drop. Addressable LEDs consume between 20 and 60mA of power each depending on how bright they are set. If they are being run on a supply that cannot supply enough power, such as the internal voltage regulator of a printer board, it could manifest as flickering or overall dimness with the strips.
This typically has to do with the LEDs at the ends of the strip not getting enough power compared to the LEDs at the beginning of the strip. The solution is to solder a VCC and GND wire to the end of the strip. These additional power lines will allow the LEDs at the ends to draw the power they need. This usually only occurs on very long strips or if the power supply is already at its limit. It is always recommended to power LEDs like this from a separate 5V source from the board.
Different chip manufacturers and chip styles use slightly different protocols for color data. Some specify the color order be Red, Green, then Blue others specify Green, Red, Blue. The configuration for the LED strip has an optional parameter that can be set in the 'neopixel' section to change the color order.
color_order: GRB
If you are unsure of the color order of your LEDs and want to test this, you can comment out or disable all of the effects you have configured and use a gcode command to set the color of the led strips directly.
SET_LED LED=<config_name> RED=1 GREEN=0 BLUE=0 TRANSMIT=1
This command should turn the entire strip red. If the strip turns green, then it uses a GRB color order.
Some LEDs, like the SK6812, also have a white channel. For that the color order can be set to:
color_order: GRBW