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NeoPixel-UserGuide-Arduino (voir la source)
Version du 24 février 2014 à 14:54
, 24 février 2014 à 14:54→Inspectons le code
<nowiki>strip.setPixelColor(n, red, green, blue);</nowiki>
<nowiki>strip.setPixelColor(n, red, green, blue);</nowiki>
The first argument — n in this example — is the pixel number along the strip, starting from 0 closest to the Arduino. If you have a strip of 30 pixels, they’re numbered 0 through 29. It’s a computer thing. You’ll see various places in the code using a for loop, passing the loop counter variable as the pixel number to this function, to set the values of multiple pixels.
The next three arguments are the pixel color, expressed as red, green and blue brightness levels, where 0 is dimmest (off) and 255 is maximum brightness.
To set the 12th pixel (#11, counting from 0) to magenta (red + blue), you could write:
<nowiki>strip.setPixelColor(11, 255, 0, 255);</nowiki>
An alternate syntax has just two arguments:
<nowiki>strip.setPixelColor(n, color);</nowiki>
Here, color is a 32-bit type that merges the red, green and blue values into a single number. This is sometimes easier or faster for some (but not all) programs to work with; you’ll see the strandtest code uses both syntaxes in different places.
You can also convert separate red, green and blue values into a single 32-bit type for later use:
<nowiki>uint32_t magenta = strip.Color(255, 0, 255);</nowiki>
Then later you can just pass “magenta” as an argument to setPixelColor rather than the separate red, green and blue numbers every time.
setPixelColor() does not have an immediate effect on the LEDs. To “push” the color data to the strip, call show():
<nowiki>strip.show();</nowiki>
This updates the whole strip at once, and despite the extra step is actually a good thing. If every call to setPixelColor() had an immediate effect, animation would appear jumpy rather than buttery smooth.
You can query the color of a previously-set pixel using getPixelColor():
<nowiki>uint32_t color = strip.getPixelColor(11);</nowiki>
This returns a 32-bit merged color value.
The number of pixels in a previously-declared strip can be queried using numPixels():
<nowiki>uint16_t n = strip.numPixels();</nowiki>
The overall brightness of all the LEDs can be adjusted using setBrightness(). This takes a single argument, a number in the range 0 (off) to 255 (max brightness). For example, to set a strip to 1/4 brightness:
<nowiki>strip.setBrightness(64);</nowiki>
Just like setPixel(), '''this does not have an immediate effect'''. You need to follow this with a call to show().
You can’t move from a lower brightness to a higher setting without some loss in fidelity. Certain animation effects are better served by leaving the brightness at max and calling setPixel() repeatedly to fill the strip.
=== I’m calling setPixel() but nothing’s happening! ===
There are two main culprits for this:
# forgetting to call strip.begin() in setup().
# forgetting to call strip.show() after setting pixel colors.
Another (less common) possibility is running out of RAM — see the last section below. If the program ''sort of'' works but has unpredictable results, consider that.
=== Can I have multiple NeoPixel objects on different pins? ===
Certainly! Each requires its own declaration with a unique name:
<nowiki>Adafruit_NeoPixel strip_a = Adafruit_NeoPixel(16, 5);
Adafruit_NeoPixel strip_b = Adafruit_NeoPixel(16, 6);</nowiki>
The above declares two distinct NeoPixel objects, one each on pins 5 and 6, each containing 16 pixels and using the implied default type (NEO_KHZ800 + NEO_GRB).
{{NeoPixel-UserGuide-TRAILER}}
{{NeoPixel-UserGuide-TRAILER}}