/Modules/AVR/Text_Examples/SW/TIMER_DEMO1/timer_demo1.c
0,0 → 1,103
// timer_demo1.c
// -------------
//
// Example file for ATmega88 (and similar AVR chips) demonstrating how to use
// timer interrupt just to blink by LED.
//
// The program uses TIMER1 to generate interrupts and the interrupt routine
// toogles the LED state. Connect LED to ground with apropriate serial resistor
// (value about 330 OHM).
//
// (c) miho 2014 http://www.mlab.cz
//
// History
// 2014 01 29 - First demo
 
 
// System Configuration
#define F_CPU 4000000 // Do not forget to set FUSEs to external XTAL osc with DIV/8 off and connect xtal
 
 
// LED Ports Configuration
#define LED_S_PORT C
#define LED_S_PIN 4
#define LED_M_PORT C
#define LED_M_PIN 5
 
 
// -------------- DO NOT EDIT BELOW THIS LINE --------------
 
 
// Library Headers
#include <avr/interrupt.h>
 
 
// Comaptibility ATmega8 / ATmega88
#ifndef TIMSK
#define TIMSK TIMSK1
#endif
 
 
// Macro for Port (enables to easily define IO signals)
#define GLUE(A,B) A##B
#define DDR(PORT_LETTER) GLUE(DDR, PORT_LETTER) // Makes DDRC from DDR(C)
#define PORT(PORT_LETTER) GLUE(PORT,PORT_LETTER) // Makes PORTC from PORT(C)
#define PIN(PORT_LETTER) GLUE(PIN, PORT_LETTER) // Makes PINC from PIN(C)
 
 
// Global Variable
volatile int Seconds;
 
// Interrupt Routine for TIMER1 Output Compare A
ISR(TIMER1_COMPA_vect)
{
// LED on/off
PORT(LED_S_PORT) ^= (1<<LED_S_PIN);
if (Seconds<59)
{
Seconds++;
}
else
{
Seconds=0;
// Toogle Minute LED
PORT(LED_M_PORT) ^= (1<<LED_M_PIN);
}
}
 
 
// Main
int main()
{
// Enable LED Output
DDR(LED_S_PORT) |= (1<<LED_S_PIN);
DDR(LED_M_PORT) |= (1<<LED_M_PIN);
 
// Set MAX value for Timer1
OCR1A = F_CPU/256/2-1; // 1/2s
 
// Set Timer1 to CTC with presacaller 1/256
// CTC Mmode counts from 0 to value stored in OCR1A
// and generates interrupt every time it goes back to 0
// CS12 CS11 CS10 Prescaller
// 0 0 1 clkI/O/1 (No prescaling)
// 0 1 0 clkI/O/8 (From prescaler)
// 0 1 1 clkI/O/64 (From prescaler)
// 1 0 0 clkI/O/256 (From prescaler)
// 1 0 1 clkI/O/1024 (From prescaler)
TCCR1B |= (1<<CS12) | (1<<WGM12);
 
// Enable Interrupt for Timer1 OCRA
TIMSK |= (1<<OCIE1A);
 
// Enable Global (CPU) Interrupt
sei();
 
// Main Loop
for(;;)
{
// Do any job here
}
 
return 0;
}