制作交通灯代码：南北方向绿灯30s，黄灯3s，东西方向绿灯15s，黄灯3s，利用数码管倒计时，红黄绿灯用LED显示

以下是一个简单的交通灯控制程序，使用Arduino IDE编写，需要连接4个LED和一个数码管。其中，南北方向的绿灯使用LED1，东西方向的绿灯使用LED2，黄灯和红灯分别使用LED3和LED4，数码管显示倒计时。

// 定义引脚
const int LED1 = 2;
const int LED2 = 3;
const int LED3 = 4;
const int LED4 = 5;
const int DIGIT1 = 6;
const int DIGIT2 = 7;

// 定义状态
const int STATE_NS_GREEN = 0;
const int STATE_NS_YELLOW = 1;
const int STATE_EW_GREEN = 2;
const int STATE_EW_YELLOW = 3;

// 定义时间参数
const int NS_GREEN_TIME = 30;
const int NS_YELLOW_TIME = 3;
const int EW_GREEN_TIME = 15;
const int EW_YELLOW_TIME = 3;

// 定义计时器
int timer = 0;

// 定义当前状态
int state = STATE_NS_GREEN;

void setup() {
  // 初始化引脚
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
  pinMode(DIGIT1, OUTPUT);
  pinMode(DIGIT2, OUTPUT);
}

void loop() {
  // 状态机控制交通灯
  switch (state) {
    case STATE_NS_GREEN:
      digitalWrite(LED1, HIGH);
      digitalWrite(LED2, LOW);
      digitalWrite(LED3, LOW);
      digitalWrite(LED4, HIGH);
      displayTime(NS_GREEN_TIME);
      if (timer >= NS_GREEN_TIME) {
        state = STATE_NS_YELLOW;
        timer = 0;
      }
      break;
    case STATE_NS_YELLOW:
      digitalWrite(LED1, LOW);
      digitalWrite(LED2, LOW);
      digitalWrite(LED3, HIGH);
      digitalWrite(LED4, HIGH);
      displayTime(NS_YELLOW_TIME);
      if (timer >= NS_YELLOW_TIME) {
        state = STATE_EW_GREEN;
        timer = 0;
      }
      break;
    case STATE_EW_GREEN:
      digitalWrite(LED1, LOW);
      digitalWrite(LED2, HIGH);
      digitalWrite(LED3, HIGH);
      digitalWrite(LED4, LOW);
      displayTime(EW_GREEN_TIME);
      if (timer >= EW_GREEN_TIME) {
        state = STATE_EW_YELLOW;
        timer = 0;
      }
      break;
    case STATE_EW_YELLOW:
      digitalWrite(LED1, LOW);
      digitalWrite(LED2, LOW);
      digitalWrite(LED3, HIGH);
      digitalWrite(LED4, HIGH);
      displayTime(EW_YELLOW_TIME);
      if (timer >= EW_YELLOW_TIME) {
        state = STATE_NS_GREEN;
        timer = 0;
      }
      break;
  }
  // 计时器加1
  timer++;
  // 等待1秒
  delay(1000);
}

// 数码管显示倒计时
void displayTime(int seconds) {
  int minute = seconds / 60;
  int second = seconds % 60;
  digitalWrite(DIGIT1, HIGH);
  digitalWrite(DIGIT2, LOW);
  displayDigit(minute);
  delay(1000);
  digitalWrite(DIGIT1, LOW);
  digitalWrite(DIGIT2, HIGH);
  displayDigit(second);
  delay(1000);
}

// 数码管显示数字
void displayDigit(int digit) {
  switch (digit) {
    case 0:
      digitalWrite(8, LOW);
      digitalWrite(9, LOW);
      digitalWrite(10, LOW);
      digitalWrite(11, LOW);
      break;
    case 1:
      digitalWrite(8, HIGH);
      digitalWrite(9, LOW);
      digitalWrite(10, LOW);
      digitalWrite(11, LOW);
      break;
    case 2:
      digitalWrite(8, LOW);
      digitalWrite(9, HIGH);
      digitalWrite(10, LOW);
      digitalWrite(11, LOW);
      break;
    case 3:
      digitalWrite(8, HIGH);
      digitalWrite(9, HIGH);
      digitalWrite(10, LOW);
      digitalWrite(11, LOW);
      break;
    case 4:
      digitalWrite(8, LOW);
      digitalWrite(9, LOW);
      digitalWrite(10, HIGH);
      digitalWrite(11, LOW);
      break;
    case 5:
      digitalWrite(8, HIGH);
      digitalWrite(9, LOW);
      digitalWrite(10, HIGH);
      digitalWrite(11, LOW);
      break;
    case 6:
      digitalWrite(8, LOW);
      digitalWrite(9, HIGH);
      digitalWrite(10, HIGH);
      digitalWrite(11, LOW);
      break;
    case 7:
      digitalWrite(8, HIGH);
      digitalWrite(9, HIGH);
      digitalWrite(10, HIGH);
      digitalWrite(11, LOW);
      break;
    case 8:
      digitalWrite(8, LOW);
      digitalWrite(9, LOW);
      digitalWrite(10, LOW);
      digitalWrite(11, HIGH);
      break;
    case 9:
      digitalWrite(8, HIGH);
      digitalWrite(9, LOW);
      digitalWrite(10, LOW);
      digitalWrite(11, HIGH);
      break;
  }
}

需要注意的是，此程序仅为示例，实际使用时需要根据实际需要进行修改和调整。例如，需要根据实际情况设置引脚和时间参数，以及添加必要的安全措施，如红灯闪烁等。