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| /*********************************************************************************************************************************** |
| * File: timer.c |
| * |
| * Purpose: sets up a flag that is coming up every 2 ms |
| * |
| * Functions: void init_Timer0(void) |
| * ISR(TIMER0_COMP_vect) |
| * unsigned char Flag2ms() |
| * |
| * hardware: AVR-Ctrl experimental board without LCD display as I2C bus is used |
| * |
| * Created: Jan 2013 |
| * |
| * Version: 1.00 experimental version |
| * |
| * Copyright: (c)2013 dk9nw -at- darc.de |
| * All rights reserved. This software is available only for non-commercial amateur radio or educational applications. |
| * Other uses are prohibited. This software may be modified only if |
| * the resulting code be made available publicly and the original author(s) given credit. |
| * |
| ***********************************************************************************************************************************/ |
| #include "timer.h" |
| |
| #include <stdlib.h> |
| #include <stdio.h> |
| #include <avr/io.h> |
| #include <avr/pgmspace.h> |
| #include <avr/interrupt.h> |
| |
| |
| volatile unsigned char c2ms = 0; // flag that switches on every 2 milliseconds |
| |
| |
| |
| // ************************************************************************************************************* |
| // Purpose: Function to init Timer0 |
| // Input: none |
| // Returns: none |
| // -------------------------------------- |
| void init_Timer0(void) |
| { |
| // TCCR0 = Timer/Counter Control Register -> FOC0 WGM00 COM01 COM00 WGM01 CS02 CS01 CS00 |
| // ------------------------------------------------------------------------------------- |
| // WGM = Waveform Generation Mode = 10 = Clear Timer on Compare Match (CTC) mode |
| TCCR0 |= (1<<WGM01); // CTC Compare Mode |
| TCCR0 &= ~(1<<WGM00); // CTC Compare Mode |
| |
| // TCCR0 = Timer/Counter Control Register -> FOC0 WGM00 COM01 COM00 WGM01 CS02 CS01 CS00 |
| // ------------------------------------------------------------------------------------- |
| // CS02 CS01 CS00 The three Clock Select bits select the clock source to be used by the Timer/Counter |
| TCCR0 |= (1<<CS02); // prescale = 100 = clkI/O/256 (From prescaler) |
| TCCR0 &= ~((1<<CS01)|(1<<CS00)); // prescale = 100 = clkI/O/256 (From prescaler) |
| |
| OCR0 = 126; // 1/(Fcpu/256) * 126 = 2.016 ms |
| |
| // TIMSK = Timer/Counter Interrupt Mask Register -> OCIE2 TOIE2 TICIE1 OCIE1A OCIE1B TOIE1 OCIE0 TOIE0 |
| // OCIE0 = Timer/Counter0 Output Compare Match Interrupt Enable |
| // |
| TIMSK |= (1<<OCIE0); // Interrupt Enabled |
| |
| c2ms = 0; |
| } |
| // *** EOF: void init_Timer0(void) **************************************************************************** |
| |
| |
| |
| |
| // *************************************************** |
| // Purpose: ISR is called at TIMER0 Compare match |
| // |
| ISR(TIMER0_COMP_vect) |
| { |
| c2ms = 1; |
| } |
| // *** EOF: ISR ************************************** |
| |
| |
| |
| |
| // ********************************************************************************************** |
| // Function returns 0 as long as the 2 msec Interrupt Flag of Timer0 is not set and resets it |
| // Input: none |
| // Returns: ck |
| // |
| unsigned char Flag2ms(void) |
| { |
| static unsigned char ck = 0; |
| |
| ck = c2ms; |
| c2ms = 0; |
| return ck; |
| } |
| // *** EOF: Flag2ms() **************************************************************************** |
| |
| |
| |
| |
| // ********************************** EOF: timer.c ************************************************************************** |