RGB LED 有四支腳，我們所用的模組為共陰極，陰極腳接地，其他三支腳位分別控制 R、G、B 色彩。

以下的電路示意與第一段程式碼，示範情境為：以 digitalWrite 對三個顏色的腳位給予不同電位，產生不同的顏色組合。

電路示意圖

RGB LED Circuit

範例程式

int red_led = 11;
int gree_led = 10;
int blue_led = 9;

void setup() {
  pinMode(red_led, OUTPUT);
  pinMode(gree_led, OUTPUT);
  pinMode(blue_led, OUTPUT);
}
void loop() {
  //0 black
  digitalWrite(red_led, LOW);
  digitalWrite(gree_led, LOW);
  digitalWrite(blue_led, LOW);
  delay(1000);
  //1 red
  digitalWrite(red_led, HIGH);
  digitalWrite(gree_led, LOW);
  digitalWrite(blue_led, LOW);
  delay(1000);
  //2 gree
  digitalWrite(red_led, LOW);
  digitalWrite(gree_led, HIGH);
  digitalWrite(blue_led, LOW);
  delay(1000);
  //3 yellow
  digitalWrite(red_led, HIGH);
  digitalWrite(gree_led, HIGH);
  digitalWrite(blue_led, LOW);
  delay(1000);
  //4 blue
  digitalWrite(red_led, LOW);
  digitalWrite(gree_led, LOW);
  digitalWrite(blue_led, HIGH);
  delay(1000);
  //5 purple
  digitalWrite(red_led, HIGH);
  digitalWrite(gree_led, LOW);
  digitalWrite(blue_led, HIGH);
  delay(1000);
  //6 Cyan
  digitalWrite(red_led, LOW);
  digitalWrite(gree_led, HIGH);
  digitalWrite(blue_led, HIGH);
  delay(1000);
  //7   white
  digitalWrite(red_led, HIGH);
  digitalWrite(gree_led, HIGH);
  digitalWrite(blue_led, HIGH);
  delay(1000);
}

程式碼二 以迴圈和 analogWrite() 產生三色輪動之燈光明滅的效果（呼吸燈）

const int led[] = {11, 10, 9};
int pinCount = sizeof(led) / sizeof(int);
int brightness = 0;
int lightenstep = 5;
int direct = 1;
int DEBUG = 1;
int delayTime = 50;

void setup() {
  for (int pin = 0 ; pin < pinCount; pin++) {
    pinMode(led[pin], OUTPUT);
    analogWrite(led[pin], brightness);
  }

  Serial.begin(9600);
}

void loop() {
  int pin = 0;
  while (pin < pinCount) {
    if (DEBUG) {
      Serial.print("=== Using Pin: ");
      Serial.print(led[pin]);
      Serial.println(" ===");
    }

    breath(pin);

    pin++;
    delay(delayTime);
  }

}

void breath(int ledNums) {
  for (int i = 0; i < 255; i += lightenstep) {
    brightness += lightenstep;
    analogWrite(led[ledNums], brightness);
    if (DEBUG) {
      Serial.println(brightness);
    }
    delay(delayTime);
  }

  for (int j = 255; j > 0; j -= lightenstep) {
    brightness -= lightenstep;
    analogWrite(led[ledNums], brightness);
    if (DEBUG) {
      Serial.println(brightness);
    }
    delay(delayTime);
  }
}

思考練習

7LEDs