Documentation
¶
Overview ¶
Package apa102 drives a strip of APA102 LEDs connected on a SPI port.
These devices are interesting because they have 2 PWMs: one global of 5 bits of resolution and one per channel of 8 bits of resolution. This means that the dynamic range is of 13 bits.
This driver handles color intensity and temperature correction and uses the full near 8000:1 dynamic range as supported by the device.
Datasheet ¶
https://cpldcpu.files.wordpress.com/2014/08/apa-102c-super-led-specifications-2014-en.pdf
Example ¶
package main
import (
"image"
"image/color"
"log"
"periph.io/x/periph/conn/spi/spireg"
"periph.io/x/periph/devices/apa102"
"periph.io/x/periph/host"
)
func main() {
// Make sure periph is initialized.
if _, err := host.Init(); err != nil {
log.Fatal(err)
}
// Use spireg SPI port registry to find the first available SPI bus.
p, err := spireg.Open("")
if err != nil {
log.Fatal(err)
}
defer p.Close()
// Opens a 300 lights strip at 50% intensity with color temperature at
// 3500°Kelvin.
o := apa102.DefaultOpts
o.NumPixels = 300
o.Intensity = 127
o.Temperature = 3500
dev, err := apa102.New(p, &o)
if err != nil {
log.Fatalf("failed to open apa102: %v", err)
}
img := image.NewNRGBA(image.Rect(0, 0, dev.Bounds().Dy(), 1))
for x := 0; x < img.Rect.Max.X; x++ {
img.SetNRGBA(x, 0, color.NRGBA{uint8(x), uint8(255 - x), 0, 255})
}
if err := dev.Draw(dev.Bounds(), img, image.Point{}); err != nil {
log.Fatal(err)
}
}
Output:
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var DefaultOpts = Opts{
NumPixels: 150,
Intensity: 255,
Temperature: 5000,
}
DefaultOpts is the recommended default options.
Functions ¶
Types ¶
type Dev ¶
type Dev struct {
// Intensity set the intensity between 0 (off) and 255 (full brightness).
//
// It can be changed, it will take effect on the next Draw() or Write() call.
Intensity uint8
// Temperature is the white adjustment in °Kelvin.
//
// It can be changed, it will take effect on the next Draw() or Write() call.
Temperature uint16
// contains filtered or unexported fields
}
Dev represents a strip of APA-102 LEDs as a strip connected over a SPI port. It accepts a stream of raw RGB pixels and converts it to the full dynamic range as supported by APA102 protocol (nearly 8000:1 contrast ratio).
Includes intensity and temperature correction.
func New ¶
New returns a strip that communicates over SPI to APA102 LEDs.
The SPI port speed should be high, at least in the Mhz range, as there's 32 bits sent per LED, creating a staggered effect. See https://cpldcpu.wordpress.com/2014/11/30/understanding-the-apa102-superled/
As per APA102-C spec, the chip's max refresh rate is 400hz. https://en.wikipedia.org/wiki/Flicker_fusion_threshold is a recommended reading.
func (*Dev) ColorModel ¶
ColorModel implements display.Drawer. There's no surprise, it is color.NRGBAModel.
type Opts ¶
type Opts struct {
// NumPixels is the number of pixels to control. If too short, the following
// pixels will be corrupted. If too long, the pixels will be drawn
// unnecessarily but not visible issue will occur.
NumPixels int
// Intensity is the maximum intensity level to use, on a logarithmic scale.
// This is useful to safely limit current draw.
Intensity uint8
// Temperature declares the white color to use, specified in Kelvin.
//
// This driver assumes the LEDs are emitting a 6500K white color.
Temperature uint16
}
Opts defines the options for the device.
Source Files