NeoPixel¶
NeoPixels are Adafruit’s brand of LED strips that can be individually controlled. The MetaWear firmware can communicate with up to 3 strands on the WS2811 protocol with the NeoPixel interface.
We have a blog post that provides instructions on how to connect a strand to a MetaWear board. Though the example code is for an older API, the usage and structure of the v3 API is similar to the v1 API.
import com.mbientlab.metawear.module.NeoPixel;
final NeoPixel neopixel = board.getModule(NeoPixel.class)
Initializing a Strand¶
Before we can interact with a NeoPixel strand, we first need to initialize memory on the MetaWear board to store NeoPixel information. To initialize the strand, call the initializeStrand method. When calling the function, you will need to take into consideration these parameters:
Operating frequency (either 800 Hz or 400 Hz)
How many LEDs to use
What color ordering the strand requires (RGB, GRB, etc.)
Which gpio pin the data wire is connected to
import com.mbientlab.metawear.module.NeoPixel.*;
// initialize memory for a strand #2 that operates at 800KHz (fast), has 60 leds,
// uses rbg color order, and has a data wire connected to gpio pin 1
Strand npStrand = neoPixel.initializeStrand((byte) 2, ColorOrdering.MW_WS2811_RBG, StrandSpeed.FAST, (byte) 1, (byte) 60);
The function returns a Strand object and can be retrieved at a later time by calling lookupStrand with the same strand number used for initializeStrand.
Strand npStrand = neoPixel.lookupStrand((byte) 2);
Setting Colors¶
When you have received your strand object, you can start turning on the LEDs using setRgb. Any changes to the led state will immediately be propogated to the strand unless a hold is enabled with the hold function. When release is called, all the LED changes will appear simultaneously.
// Enable hold to lock the strand state
npStrand.hold();
npStrand.setRgb((byte) 0, (byte) 255, (byte) 0, (byte) 0);
npStrand.setRgb((byte) 1, (byte) 0, (byte) 255, (byte) 0);
npStrand.setRgb((byte) 2, (byte) 0, (byte) 0, (byte) 255);
// Disable hold, which will now update the strand with any state changes
npStrand.release();
Pattern Rotation¶
Once you have a color pattern on your strand, you can rotate the pattern indefinitely using rotate or its variant function to specify a fixed number of rotations. If using the former method, call stopRotation to terminate the rotation.
import com.mbientlab.metawear.module.NeoPixel.Strand.RotationDirection;
// Rotate pattern 16 times, moving away from the board with a delay of 500ms
npStrand.rotate(RotationDirection.AWAY, (byte) 16, (short) 500);
// Rotate pattern indefinitely, moving towards the board with a delay of 250ms
npStrand.rotate(RotationDirection.TOWARDS, (short) 250);
// Stop pattern rotation
npStrand.stopRotation();