Generating 8 MHz clock using Arduino Micro

Projects Programming
10

matt_s:
I've found the problem: The bit WGM12 is actually in TCCR1B, not TCCR1A. The code below is working, generating a 8 MHz clock on pin 9 (Arduino Micro). Thanks to everybody for the help!

//

//
// Use of timer1 to generate 8 Mhz clock on pin 9
//
//

const int freqOutputPin = 9;  // OC1A output pin for ATmega32u4 (Arduino Micro)

// Constants are computed at compile time

// If you change the prescale value, it affects CS22, CS21, and CS20
// For a given prescale value, the eight-bit number that you
// load into OCR1A determines the frequency according to the
// following formulas:
//
// With no prescaling, an ocr1val of 0 causes the output pin to
// toggle the value every  CPU clock cycle. That is, the
// period is equal to two clock cycles.
//
// With F_CPU = 16 MHz, the result is 8 MHz.
//
 
// To change the timer prescale division, use different bits for CS22:0 below

const int ocr1aval  = 0;

void setup()
{
    pinMode(freqOutputPin, OUTPUT);

// Set Timer 1 CTC mode with no prescaling.  OC1A toggles on compare match
    //
    // WGM12:0 = 010: CTC Mode, toggle OC
    // WGM2 bits 1 and 0 are in TCCR1A,
    // WGM2 bit 2 and 3 are in TCCR1B
    // COM1A0 sets OC1A (arduino pin 9 on Arduino Micro) to toggle on compare match
    //
    TCCR1A = ( (1 << COM1A0));

// Set Timer 1  No prescaling  (i.e. prescale division = 1)
    //
 
    TCCR1B = ((1 << WGM12) | (1 << CS10));

// Make sure Compare-match register A interrupt for timer1 is disabled
    TIMSK1 = 0;
    // This value determines the output frequency
    OCR1A = ocr1aval;

}

void loop()
{
    //
}

Is there a way to modify the code to output 4MHz? I'm pretty good with Arduinos but I am SO lost with this....