How to use timer 0 in arduino to make 8 MHz PWM?

Projects Programming
1

Hi. Recently i'm working on the ov7670 camera and i need to supply it with a 8Mhz clock rate. I tried googling about that, and only found a solution on timer 1. I tried to look up the datasheet, but somehow my code fails to work.
const int
D0 = A0,
D1 = A1,
D2 = A2,
D3 = A3,
D4 = 4,
D5 = 5,
D6 = 6,
D7 = 7, // D0:8 are the output pins from ov7670
XCLK_pin = 6; // OC1A output pin for ATmega32u4 (Arduino Micro)

void setup()
{
  /*
  * TCCR0A Bits 7:0
  * +-------+-------+-------+-------+-------+-------+-------+-------+
  * | COM0A1| COM0A0| COM0B1| COM0B0|   -   |   –   | WGM01 | WGM00 |
  * +-------+-------+-------+-------+-------+-------+-------+-------+
  */
  /*
  * TCCR0B Bits 7:0
  * +-------+-------+-------+-------+-------+-------+-------+-------+
  * | FOC0A | FOC0B |   -   |   –   | WGM02 |  CS02 |  CS01 |  CS00 |
  * +-------+-------+-------+-------+-------+-------+-------+-------+
  */
  
  pinMode(XCLK_pin, OUTPUT);
  TCCR0A = TCCR0B = 0;
  
  // toggle mode
  TCCR0A &= ~bit(COM0A0);
  TCCR0A |=  bit(COM0A1);
  
  // don't use timer B
  TCCR0A &= ~bit(COM0B0);
  TCCR0A &= ~bit(COM0B1);
  
  // fast PWM mode with TOP = OCR0A
  TCCR0B |=  bit(WGM02);
  TCCR0A |=  bit(WGM01);
  TCCR0A |=  bit(WGM00);
  
  // not using force output
  TCCR0B &= ~bit(FOC0A);
  TCCR0B &= ~bit(FOC0B);
  
  // not using prescaler
  TCCR0B &= ~bit(CS02);
  TCCR0B &= ~bit(CS01);
  TCCR0B |=  bit(CS00);
  
  OCR0A = TCNT0 = 0;
  Serial.begin(9600);
}

void loop() {
  Serial.println(F("hello"));
  delay(1000);
}

The serial monitor just printed "he" and stopped. I cannot figure why this happened. Any help is much appreciated. Thanks.

2

Timer0 is used for millis() and delay() and should not be modified.

Use Timer1 or 2. You might study Nick Gammon's excellent tutorial on timers.

In any case, you can't produce 8 MHz PWM using the Arduino. You can have an 8 MHz signal output. Here is how to do it with Timer1:

  // set up 8 MHz timer on pin 9
  pinMode (9, OUTPUT);
  // set up Timer 1
  TCCR1A = bit (COM1A0);  // toggle OC1A on Compare Match
  TCCR1B = bit (WGM12) | bit (CS10);   // CTC, no prescaling
  OCR1A =  0;       // output every cycle