即使串行可用，代码也会不断循环

Question

I'm using an external application to sync my RGB peripherals with my WS2812B Strip. I wanted to make a default color that it could switch to when the application isn't running but after 2 seconds of enabling the strip in the software, it goes back to the default color I set (255,255,255).

#include <Adafruit_NeoPixel.h> 
#define PIN 6
#define NUMPIXELS 30

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + 
NEO_KHZ800);

void setup() {
  pixels.begin();
  Serial.begin(19200, SERIAL_8E1);
}

void loop() {
  for (int w = 0; w < NUMPIXELS; w++) {
    pixels.setPixelColor(w, 255, 255, 255);
  }    
  pixels.show();
  int w = 0;
  if (Serial.available()) {
    int n = 0;
    for (int n = 0; n < 3; n++) {
      byte rgb[3];
      Serial.readBytes(rgb, 3);
      uint32_t r = int(rgb[0]);
      uint32_t g = int(rgb[1]);
      uint32_t b = int(rgb[2]);
      for (int i = 0; i < NUMPIXELS; i++) {
        pixels.setPixelColor(i, r, g, b);
      }
      pixels.show();
    }
  }
}

Answer 1

The function Serial.available() does something else than what you expect:

You expect it to return if there is a communication partner available. Instead it checks if there are bytes to read available:

Get the number of bytes (characters) available for reading from the serial port. (Source: https://www.arduino.cc/en/Serial/Available )

This means: Your Arduino has run out of bytes to read, because it empties the pipeline too fast. So, as there are no more bytes to read, it will just make the leds show white.

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Sidenote: The if condition should be changed to reflect this (see post on Arduino website):

if (Serial.available() > 0) {