使用arduino nano的串口来控制继电器作为数字开关

switch.ino

#define VCC 2
#define IN 4


const int HEADER = '@';
const char TAIL = '%';

int flag =-1;

void setup() {
  Serial.begin(9600);//打开串口波特率9600
  pinMode(VCC,OUTPUT);
  pinMode(IN,OUTPUT);
  digitalWrite(VCC,HIGH);
  digitalWrite(IN,LOW); //default off for safety
}
 
void loop() {
  if (Serial.available())//判读是否串口有数据
  {
    if (Serial.read() == HEADER)
    {
        delay(3);
        flag = Serial.read();
        Serial.print("received");
        Serial.print(char(flag));
        Serial.print('\n');
        if(Serial.read() == TAIL)
        {
              if(flag== '1')
              { 
                digitalWrite(IN,HIGH);
                Serial.println("IN on"); 
                flag = -1;
              }
              if(flag=='0')
              {
                digitalWrite(IN,LOW);
                Serial.println("IN off");
                flag = -1;
              }
        }

    }
  }
 }