Arduino Nano代码在Arduino IDE可编译但VSC报ai0/ai1未声明问题咨询

• 你碰到的'ai0' was not declared in this scope 'ai1' was not declared in this scope报错的核心是Arduino IDE和VS Code的编译预处理逻辑存在差异：Arduino IDE会自动为所有用户定义的函数生成前置声明，不需要手动编写，所以代码能正常编译；但VS Code中使用的Arduino编译工具链（包括PlatformIO、官方Arduino扩展的默认编译逻辑）没有这个自动处理步骤，函数如果在定义之前被调用，就会报未声明的错误。
• 另外当前代码还缺少全局变量counter和temp的定义，解决完函数声明的问题后还会报这两个变量未声明的错误，需要同步修复。

在代码最开头、setup()函数之前补充函数前置声明和全局变量定义即可，完整修复后的代码如下：

// 补充全局变量定义，中断内修改的变量需要加volatile防止编译器优化
volatile int counter = 0;
int temp = 0;

// 补充中断函数的前置声明
void ai0();
void ai1();

void setup() {
  Serial.begin (9600);

  pinMode(2, INPUT_PULLUP); // internal pullup input pin 2 

  pinMode(3, INPUT_PULLUP); // internal pullup input pin 3
  //Setting up interrupt
  //A rising pulse from encodenren activated ai0(). AttachInterrupt 0 is DigitalPin nr 2 on moust Arduino.
  attachInterrupt(0, ai0, RISING);
 
  //B rising pulse from encodenren activated ai1(). AttachInterrupt 1 is DigitalPin nr 3 on moust Arduino.
  attachInterrupt(1, ai1, RISING);
}
 
void loop() {
  // Send the value of counter
  if( counter != temp ){
    Serial.println (counter);
    temp = counter;
  }
}
 
void ai0() {
  // ai0 is activated if DigitalPin nr 2 is going from LOW to HIGH
  // Check pin 3 to determine the direction
  if(digitalRead(3)==LOW) {
    counter++;
  }else{
    counter--;
  }
}
 
void ai1() {
  // ai1 is activated if DigitalPin nr 3 is going from LOW to HIGH
  // Check with pin 2 to determine the direction
  if(digitalRead(2)==LOW) {
    counter--;
  }else{
    counter++;
  }
}

内容的提问来源于stack exchange，提问作者Al1er