问Arduino上的Timer1使串行打印无法正常工作

EN

/*
timer1-arduino-makes-serial-not-work.ino
- a demo to help out this person here: 
  http://stackoverflow.com/questions/28880226/timer1-arduino-makes-serial-not-work

By Gabriel Staples
http://electricrcaircraftguy.blogspot.com/

5 March 2015
- using Arduino 1.6.0
*/

// Note: ISR stands for Interrupt Service Routine

// Global variables
volatile unsigned long numISRcalls = 0; // number of times the ISR is called

void setup() 
{
  Serial.begin(115200);

  // http://www.instructables.com/id/Arduino-Timer-Interrupts/?ALLSTEPS

//  noInterrupts(); // Not necessary

  TCCR1A = 0; // set entire TCCR1A register to 0
  TCCR1B = 0; // same for TCCR1B
  TCNT1  = 0; // initialize counter value to 0
  
  // better to put this line AFTER configuring TCCR1A and TCCR1B below, but in
  // Arduino 1.6.0 it appears to be ok here (may crash code in older versions),
  // see comment by "Thorsten" here:
  // http://www.righto.com/2009/07/secrets-of-arduino-pwm.html?showComment=1297626476152#c2692242728647297320
  OCR1A = 20; 
  // SETTING OCR1A TO 1 OR 2 FOR SURE BREAKS THE CODE, as it calls the interrupt
  // too often to even allow the main loop to run at all.
  // OCR1A = 1;
  
  // turn on CTC mode [Clear Timer on Compare match---to make timer restart at
  // OCR1A; see datasheet pg. 133]
  TCCR1B |= (1 << WGM12); 
  // Set CS11 bit for 8 prescaler [0.5us ticks, datasheet pg. 135]. Each timer
  // has a different bit code to each prescaler
  TCCR1B |= (1 << CS11);
  // enable timer compare match 1A interrupt; NOW YOU *MUST* SET UP THE
  // CORRESPONDING ISR OR THIS LINE BREAKS THE CODE

  // IT IS RECOMMENDED TO SET OCR1A HERE, *after* first configuring both the
  // TCCR1A and TCCR1B registers, INSTEAD OF ABOVE! Like this:
  // OCR1A = 20; 

  TIMSK1 |= (1 << OCIE1A);

//  interrupts(); // Not necessary

  Serial.println("setup done, input a character");
}

void loop() 
{
  if (Serial.available()) 
  {
    // read and throw away the first byte in the incoming serial buffer (or else
    // the next line will get called every loop once you send the Arduino a
    // single char)
    Serial.read(); 
    Serial.println("a");
    
    // also print out how many times OCR1A has been reached by Timer 1's counter 
    noInterrupts(); // turn off interrupts while reading non-atomic (> 1 byte) 
                    // volatile variables that could be modified by an ISR at
                    // any time--incl while reading the variable itself.
    unsigned long numISRcalls_copy = numISRcalls;
    interrupts();
    Serial.print("numISRcalls = "); Serial.println(numISRcalls_copy);
  }
    
//  Serial.println("test");
//  delay(1000);
}

// SINCE YOU ARE ENABLING THE COMPARE MATCH 1A INTERRUPT ABOVE, YOU *MUST*
// INCLUDE THIS CORRESPONDING INTERRUPT SERVICE ROUTINE CODE
ISR(TIMER1_COMPA_vect)
{
  // insert your code here that you want to run every time the counter reaches
  // OCR1A
  numISRcalls++;
}

void setup() {
    Serial.begin(115200);

    TCCR1A = 0; // set entire TCCR1A register to 0
    TCCR1B = 0; // same for TCCR1B
    TCNT1  = 0; // initialize counter value to 0
    
    // turn on CTC mode
    TCCR1B |= (1 << WGM12);
    // Set CS11 bit for 8 prescaler. Each timer has a different bit code to each
    // prescaler
    TCCR1B |= (1 << CS11);

    OCR1A = 20;

    // enable timer compare interrupt
    TIMSK1 |= (1 << OCIE1A);
}

void loop() {
    //if (Serial.available()) {
    //    Serial.println("a");
    //}
    
    Serial.println("a");
    delay(500);
}

// ISR(TIMER1_COMPA_vect)
// {
//   // insert your code here that you want to run every time the counter reaches
//   // OCR1A
// }

void setup() {
    Serial.begin(115200);

    TCCR1A = 0; // set entire TCCR1A register to 0
    TCCR1B = 0; // same for TCCR1B
    TCNT1  = 0; // initialize counter value to 0
    
    // turn on CTC mode
    TCCR1B |= (1 << WGM12);
    // Set CS11 bit for 8 prescaler. Each timer has a different bit code to each
    // prescaler
    TCCR1B |= (1 << CS11);

    OCR1A = 20;

    // enable timer compare interrupt
    TIMSK1 |= (1 << OCIE1A);
}

void loop() {
    //if (Serial.available()) {
    //    Serial.println("a");
    //}
    
    Serial.println("a");
    delay(500);
}

ISR(TIMER1_COMPA_vect)
{
  // insert your code here that you want to run every time the counter reaches
  // OCR1A
}

EMPTY_INTERRUPT (TIMER1_COMPA_vect);

OCR1A = 1;

TCCR1B |= (1 << WGM12);
TCCR1B |= (1 << CS11);

TCCR1A |= (1 << WGM12);
TCCR1B |= (1 << CS11);