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