arduino生成38KHz问题

[ArdyPro]

参照网上ladyada的代码写了一个红外发送的程序，需要用arduino生成38KHz的载波，我已经根据MEGA1280调整了高低电平延时，连续高电平在1000μs之内是，生成的载波误差比较小，但是发现有两个连续高电平7190μs和9130μs的情况时，误差太大到难以理解。下面第一组数据，本来是需要连续9130μs的高电平，按照26μs一个周期，则需要351个周期，实际是用了352个周期，花费816μs，相当于每个周期才2.3μs，远低于单个指令之后的延时6μs！

各位亲们，帮我看看程序到底错在哪里。

//源代码片段

程序代码

// This procedure sends a 38KHz pulse to the IRledPin 
// for a certain # of microseconds. We'll use this whenever we need to send codes

void pulseIR(long microsecs, long Interval) 
{
     // we'll count down from the number of microseconds we are told to wait
    Serial.print(microsecs);
  
    long i;   i= micros();
    long c;   c=0;  //
  
    cli();  // this turns off any background interrupts
    while (microsecs > 0) 
      {
        // 38 kHz is about 13 microseconds high and 13 microseconds low
       digitalWrite(IRledPin, HIGH);  // this takes about 3 microseconds to happen
       delayMicroseconds(Interval);         // hang out for 10 microseconds
       digitalWrite(IRledPin, LOW);   // this also takes about 3 microseconds
       delayMicroseconds(Interval);         // hang out for 10 microseconds
       // so 26 microseconds altogether
       microsecs -= 26;
       c++;
     }

    sei();  // this turns them back on
    i = micros() -i;
  
    Serial.print("  ");  Serial.print(c );  Serial.print("cycles and takes  ");
    Serial.print(i);  Serial.println(" us");
}

//跟踪信息
9130  352cycles and takes  816 μs   <--误差很大，每个cycle才2.3μs，难以理解
850  33cycles and takes  856 μs
....
560  22cycles and takes  572 μs
7190  277cycles and takes  948 μs   <--误差很大
560  22cycles and takes  572 μs




[/size]

[ArdyPro]

int IRledPin =  13;    // LED connected to digital pin 13
int _38HZ_Space=6;     //38KHz interval

//定义按键的波形特征码
long PowerOnArray[][2]=
{
  1,913,0,412,1,85,0,22,1,87,0,23,1,87,0,25,1,85,0,25,1,85,0,26,1,85,0,
  27,1,83,0,27,1,84,0,27,1,84,0,138,1,83,0,138,1,83,0,138,1,82,0,138,1,
  82,0,139,1,82,0,140,1,80,0,32,1,75,0,144,1,76,0,146,1,74,0,38,1,69,0,
  153,1,66,0,156,1,64,0,46,1,64,0,47,1,63,0,48,1,61,0,50,1,59,0,51,1,59,
  0,163,1,56,0,55,1,56,0,55,1,55,0,166,1,56,0,165,1,56,0,166,1,55,0,165,
  1,56,0,4021,1,719,0,209,1,56,0,0
};

void setup()   {               
  // initialize the IR digital pin as an output:
  pinMode(IRledPin, OUTPUT);     

  Serial.begin(9600);
}

void loop()                     
{
  //Serial.println("Sending IR signal");

  char Recv;

  if (Serial.available()>0)
  {
    //Serial.println("Has incoming chars");
    Recv=Serial.read();
    Serial.println(Recv);

    switch (Recv)
    {
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      {
        Serial.println("Power On...");
        _38HZ_Space = Recv - 48;
        Serial.println(_38HZ_Space);
        PowerOn();
        break;
      };
    default:
      { 
      };
    }
  }

  //delay(60*1000);  // wait one minute (60 seconds * 1000 milliseconds)
}

void PowerOn()
{
  long i,c;
  long cmd,value;
  c=sizeof(PowerOnArray)/sizeof(PowerOnArray[0][0]);
  for (i=0; i<=c; i++)
  {
    cmd=PowerOnArray[0];
    value=PowerOnArray[1];
    if (cmd==1)
      pulseIR(value*10,_38HZ_Space);
    else
      delayMicroseconds(value*10);
  }
}

// This procedure sends a 38KHz pulse to the IRledPin
// for a certain # of microseconds. We'll use this whenever we need to send codes

void pulseIR(long microsecs, long Interval) {
  // we'll count down from the number of microseconds we are told to wait
  Serial.print(microsecs);

  long i;   
  i= micros();
  long c;   
  c=0;  //

  cli();  // this turns off any background interrupts
  while (microsecs > 0) {
    // 38 kHz is about 13 microseconds high and 13 microseconds low
    digitalWrite(IRledPin, HIGH);  // this takes about 3 microseconds to happen
    delayMicroseconds(Interval);         // hang out for 10 microseconds
    digitalWrite(IRledPin, LOW);   // this also takes about 3 microseconds
    delayMicroseconds(Interval);         // hang out for 10 microseconds
    // so 26 microseconds altogether
    microsecs -= 26;
    c++;
  }
  sei();  // this turns them back on
  i = micros() -i;

  Serial.print("  "); 
  Serial.print(c ); 
  Serial.print("cycles and takes  ");
  Serial.print(i); 
  Serial.println(" us");
}

后面部分怎么变成斜体了？

[Contra]

貌似编辑器最近很脆弱。。。

[ArdyPro]

我在官网咨询了一下，建议注释掉cli()和sei()，结果似乎正常，需要验证一下。至于原来代码中为什么要调用它俩，希望有明白的兄弟给解释一下。

[ChocolateUniverse]

我觉得是怕中断影响Timer，因为后面的代码是完全按照既定时间来操作的。