Arduino Timers: Complete Usage Guide

Core Concept: Arduino microcontrollers (ATmega328P/ATmega2560) contain dedicated hardware timers that handle time-sensitive operations independently of the CPU.

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1. Available Timers by Board

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2. Critical Timer Applications

A. PWM Generation

• Timer-controlled pins marked with ~ (3,5,6,9,10,11 on Uno)

• Frequency adjustment example:

  cpp

    // Set Timer1 PWM to 4kHz (default ~490Hz)
    TCCR1B = (TCCR1B & 0b11111000) | 0x02;
  

B. Precise Event Scheduling

• Hardware interrupts vs software delays:

  cpp

    // Hardware-timed (accurate)
    TIMSK1 |= (1 << OCIE1A); 
    OCR1A = 15999; // 1ms @ 16MHz/1 prescaler
  
    // Software delay (inaccurate)
    delay(1); // Varies with interrupts
  

C. Motor Control

• Servo library uses Timer1 (conflicts with AnalogWrite on 9,10)

• Advanced ESC control requires 16-bit timers

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3. Register-Level Configuration

Timer1 Setup for 1Hz Interrupt:

cpp

void setupTimer1() {
  noInterrupts();
  TCCR1A = 0; // Clear control registers
  TCCR1B = 0;
  TCNT1 = 0;  // Reset counter

  // Compare match value for 1Hz
  OCR1A = 15624; // 16MHz/1024 prescaler - 1

  TCCR1B |= (1 << WGM12); // CTC mode
  TCCR1B |= (1 << CS12) | (1 << CS10); // 1024 prescaler
  TIMSK1 |= (1 << OCIE1A); // Enable interrupt
  interrupts();
}

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4. Common Pitfalls & Solutions

1. Resource Conflicts

   • Symptom: Servo jitter when using tone()

   • Fix: Use separate timers (Servo→Timer1, tone→Timer2)

2. PWM Frequency Limitations

   • 8-bit timers max out at ~62.5kHz (16MHz/256)

   • Solution: Use 16-bit timers or clock dividers

3. ISR Timing Drift

   • Always clear overflow flags:

cpp

    ISR(TIMER1_OVF_vect) {
      TIFR1 |= (1 << TOV1); // Clear flag
      // Your code
    }

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5. Advanced Techniques

Phase-Correct PWM (for motor control):

cpp

TCCR1A = (1 << COM1A1) | (1 << WGM10);
TCCR1B = (1 << CS10); // No prescaling

Input Capture (for frequency measurement):

cpp

TCCR1B |= (1 << ICES1); // Rising edge capture
TIMSK1 |= (1 << ICIE1); // Enable capture interrupt

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6. Performance Considerations

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7. Debugging Tips

1. Verify timer clock source:

   cpp

    Serial.println(TCCR1B & 0x07); // Prescaler bits
   

2. Check for overflow:

   cpp

    if(TIFR1 & (1 << TOV1)) { /* Handle overflow */ }
   

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When to Use Which Timer

• Timer0: System functions (don't modify)

• Timer1: High-resolution control (16-bit)

• Timer2: Audio applications (8-bit with async operation)

For time-critical applications (quadcopter flight controllers, digital signal processing), always use hardware timers instead of software timing functions.