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我正在寻找一些帮助我尝试学习计时器中断的困惑的东西

您最好将我视为新手。除了学习一些我认为可以加到我的帽子上的有用羽毛以外，我这里没有其他目标！

我写了下面的草图作为一个僵硬的框架，用于以不同的速度执行不同的fcn。我已经使用millis（）做过类似的事情，并且在工作的同时，我发现它很优雅，a）没有明显的方法来检查任务超限和备份执行率，b）通过检查millis（）来捆绑处理器）每个程序周期。*

基本上，我认为应该在Timer2上发生1ms的定时器中断（16MHz / 64预分频器/ 250比较寄存器= 1000hz）出现在0.5ms左右。我已经为此困惑了几个小时，但我准备接受这可能是基础/基本的事情！

工作中还产生了一个问题，那就是使用串行通讯来尝试和调试更快的任务速率似乎会大大降低速度，因此我通过计算1ms任务来调用10,100和1000ms任务来推断问题。调试速度较慢。我想以9600baud的速度咀嚼几个字符可能很慢。**

我粘贴了以下代码。任何指针高度赞赏。随心所欲：）

欢呼

Al

*虽然我不感到困惑，但也欢迎对我的逻辑发表任何评论 **尽管我不了解Serial.println如何降低程序速度。它是由中断驱动的，因此它肯定应该只删除通信并执行下一个ISR-实际上是任务超限。这里的任何评论也欢迎

//NOTES
//https://www.robotshop.com/letsmakerobots/arduino-101-timers-and-interrupts
//https://sites.google.com/site/qeewiki/books/avr-guide/timers-on-the-atmega328
//http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-42735-8-bit-AVR-Microcontroller-ATmega328-328P_Datasheet.pdf
//

//INITIALISE EVERYTHING

const int ledPin = 13;
volatile int nStepTask1ms = 0; // init 0 - to be used for counting number of 1ms tasks run and hence calling 10ms task
volatile int nStepTask10ms = 0;
volatile int nStepTask100ms = 0;
volatile int nStepTask1000ms = 0;
volatile int LEDFlashState = 0; // init 0 - variable to flip when LED on
volatile int millisNew = 0; // to store up to date time
volatile int millisOld = 0; // to store prev time
volatile int millisDelta = 0; // to store deltas

//
void setup() 
{
Serial.begin(9600); //set up serial comms back to PC
pinMode(ledPin,OUTPUT); //to flash the embedded LED

noInterrupts(); //turn off interrupts while we set the registers
//set up TIMER first

TCCR2A = 0; //sets TCCR1A byte to zero, bits to be later individually mod'd
TCCR2B = 0; //sets TCCR1B byte to zero, bits to be later individually mod'd
TCNT2 = 0; //ensures counter value starting from zero
Serial.println("Timer1 vars reset");

TCCR2B |= (1<<WGM12); // bitwise or between itself and WGM12. TCCR2B = TCCR2B | 00001000. Sets WGM12 high. (CTC mode so WGM12=1, WGM 13,11,10 all 0) https://stackoverflow.com/questions/141525/what-are-bitwise-shift-bit-shift-operators-and-how-do-they-work
Serial.println("Mode 4 CTC set");
Serial.println("TCCR2B=");
Serial.println(TCCR2B,BIN);

TCCR2B |= (1<<CS11); // sets CS11 high
TCCR2B |= (1<<CS10); // sets CS10 high (i.e. this and above give /64 prescaler)
Serial.println("Prescaler set to 64");

OCR2A = 250; //compare match register for timer2
Serial.println("Compare Register set");
Serial.println("OCR2A=");
Serial.println(OCR2A);

TIMSK2 |= (1 << OCIE2A); //enables interrupts - https://playground2014.wordpress.com/arduino/basics-timer-interrupts/
Serial.println("Interrupt Mask Register Set");
Serial.println("TIMSK2=");
Serial.println(TIMSK2);

interrupts(); //enable interrupts again - not sure if this is required given OCIE1A being set above?
}

//set up ISR for Timer2 - timer structure called every interrump (1ms) that subsequently calls 1,10,100 and 1000msec task fcns
ISR(TIMER2_COMPA_vect)
{
TASK_1ms();
if (nStepTask1ms>9)
  {
    TASK_10ms();
    if (nStepTask10ms>9)
      {
        TASK_100ms();
        if (nStepTask100ms>9)
          {
            TASK_1000ms();
          }
      }
  }
}

void TASK_1ms()
{
  // 1ms tasks here
  nStepTask1ms++;
}

void TASK_10ms()
{
  //10ms tasks here
  nStepTask1ms=0;
  nStepTask10ms++;
}

void TASK_100ms()
{
  //100ms tasks here
  nStepTask10ms=0;
  nStepTask100ms++;
  //Serial.println(nStepTask100ms);
}

void TASK_1000ms()
{
  //1000ms tasks here
  nStepTask100ms=0;


  //do something 
  changeLEDFlashState();

  //check timing tick of this task
  millisNew=millis();
  millisDelta=millisNew-millisOld;
  Serial.println(millisDelta);
  millisOld=millisNew;

  nStepTask1000ms++; 
}

void changeLEDFlashState()
{
if(LEDFlashState==0)
{
  digitalWrite(ledPin,HIGH);
  LEDFlashState=1;
  //Serial.println("LED Turned On");
}
else
{
  digitalWrite(ledPin,LOW);
  LEDFlashState=0;
  //Serial.println("LED Turned Off");
}
}


void loop() 
{
// empty
}

Answer 1

您在这里有两行：

TCCR2B |= (1<<CS11); // sets CS11 high
TCCR2B |= (1<<CS10); // sets CS10 high (i.e. this and above give /64 prescaler)

这两行将TCCR2B的低三位设置为011，即/ 32预分频器。

请注意，对于Timer1和Timer2，预分频器设置与Timer0不同。对于Timer0，上面的设置将为您提供/ 64预分频器。

Arduino CTC计时器中断快约2倍

1 个答案: