Getting Started

Chapter 7: Microcontroller Interrupts and Timers

value

se Correct mode, CLK/8 prescaler

GM01)|(1<<WGM00)|(1<<CS01);

id s ount)

mpare value

ccurs twice per Millisec, timed for PWM

RTD &= 1) cbi(PORTD, 0);

else sbi(PORTD, 0);

once per second

1000)

d = speed; // store most recent speed in Hz

IGNAL(SIG_PIN_CHANGE1)

le changes. We reused the pin interrupt code from

he interrupt routine we increment a speed counter

opy the speed counter value to ‘lastspeed’ variable,

z when requested.

mbering to reset the AVRStudio programming tool to use

omm.hex, which I forgot AGAIN! Open HyperTerminal, toggle

// Sets the compare
setOCR0A(count);

// Set PWM Pha
TCCR0A = (0<<FOC0A)|(0<<W

}

vo etOCR0A(unsigned char c
{
// Sets the co
OCR0A = count;
}

// Interrupt o
SIGNAL(SIG_OUTPUT_COMPARE0)
{
// Toggle PORTD pin 0
if(PO

// get the speed count
if(second++ >=
{
second = 0;
lastspee

speed = 0;
}
}

S
{
speed++;
}

We’ve made a couple of simp
the joystick software and in t
variable. Once per second we c
which we report as the speed in H

Compile and load, reme
the correct PC_C