Details | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2203 | - | 1 | /*********************************************************************************************************************************** |
| 2 | * File: timer.c |
||
| 3 | * |
||
| 4 | * Purpose: sets up a flag that is coming up every 2 ms |
||
| 5 | * |
||
| 6 | * Functions: void init_Timer0(void) |
||
| 7 | * ISR(TIMER0_COMP_vect) |
||
| 8 | * unsigned char Flag2ms() |
||
| 9 | * |
||
| 10 | * hardware: AVR-Ctrl experimental board without LCD display as I2C bus is used |
||
| 11 | * |
||
| 12 | * Created: Jan 2013 |
||
| 13 | * |
||
| 14 | * Version: 1.00 experimental version |
||
| 15 | * |
||
| 16 | * Copyright: (c)2013 dk9nw -at- darc.de |
||
| 17 | * All rights reserved. This software is available only for non-commercial amateur radio or educational applications. |
||
| 18 | * Other uses are prohibited. This software may be modified only if |
||
| 19 | * the resulting code be made available publicly and the original author(s) given credit. |
||
| 20 | * |
||
| 21 | ***********************************************************************************************************************************/ |
||
| 22 | #include "timer.h" |
||
| 23 | |||
| 24 | #include <stdlib.h> |
||
| 25 | #include <stdio.h> |
||
| 26 | #include <avr/io.h> |
||
| 27 | #include <avr/pgmspace.h> |
||
| 28 | #include <avr/interrupt.h> |
||
| 29 | |||
| 30 | |||
| 31 | volatile unsigned char c2ms = 0; // flag that switches on every 2 milliseconds |
||
| 32 | |||
| 33 | |||
| 34 | |||
| 35 | // ************************************************************************************************************* |
||
| 36 | // Purpose: Function to init Timer0 |
||
| 37 | // Input: none |
||
| 38 | // Returns: none |
||
| 39 | // -------------------------------------- |
||
| 40 | void init_Timer0(void) |
||
| 41 | { |
||
| 42 | // TCCR0 = Timer/Counter Control Register -> FOC0 WGM00 COM01 COM00 WGM01 CS02 CS01 CS00 |
||
| 43 | // ------------------------------------------------------------------------------------- |
||
| 44 | // WGM = Waveform Generation Mode = 10 = Clear Timer on Compare Match (CTC) mode |
||
| 45 | TCCR0 |= (1<<WGM01); // CTC Compare Mode |
||
| 46 | TCCR0 &= ~(1<<WGM00); // CTC Compare Mode |
||
| 47 | |||
| 48 | // TCCR0 = Timer/Counter Control Register -> FOC0 WGM00 COM01 COM00 WGM01 CS02 CS01 CS00 |
||
| 49 | // ------------------------------------------------------------------------------------- |
||
| 50 | // CS02 CS01 CS00 The three Clock Select bits select the clock source to be used by the Timer/Counter |
||
| 51 | TCCR0 |= (1<<CS02); // prescale = 100 = clkI/O/256 (From prescaler) |
||
| 52 | TCCR0 &= ~((1<<CS01)|(1<<CS00)); // prescale = 100 = clkI/O/256 (From prescaler) |
||
| 53 | |||
| 54 | OCR0 = 126; // 1/(Fcpu/256) * 126 = 2.016 ms |
||
| 55 | |||
| 56 | // TIMSK = Timer/Counter Interrupt Mask Register -> OCIE2 TOIE2 TICIE1 OCIE1A OCIE1B TOIE1 OCIE0 TOIE0 |
||
| 57 | // OCIE0 = Timer/Counter0 Output Compare Match Interrupt Enable |
||
| 58 | // |
||
| 59 | TIMSK |= (1<<OCIE0); // Interrupt Enabled |
||
| 60 | |||
| 61 | c2ms = 0; |
||
| 62 | } |
||
| 63 | // *** EOF: void init_Timer0(void) **************************************************************************** |
||
| 64 | |||
| 65 | |||
| 66 | |||
| 67 | |||
| 68 | // *************************************************** |
||
| 69 | // Purpose: ISR is called at TIMER0 Compare match |
||
| 70 | // |
||
| 71 | ISR(TIMER0_COMP_vect) |
||
| 72 | { |
||
| 73 | c2ms = 1; |
||
| 74 | } |
||
| 75 | // *** EOF: ISR ************************************** |
||
| 76 | |||
| 77 | |||
| 78 | |||
| 79 | |||
| 80 | // ********************************************************************************************** |
||
| 81 | // Function returns 0 as long as the 2 msec Interrupt Flag of Timer0 is not set and resets it |
||
| 82 | // Input: none |
||
| 83 | // Returns: ck |
||
| 84 | // |
||
| 85 | unsigned char Flag2ms(void) |
||
| 86 | { |
||
| 87 | static unsigned char ck = 0; |
||
| 88 | |||
| 89 | ck = c2ms; |
||
| 90 | c2ms = 0; |
||
| 91 | return ck; |
||
| 92 | } |
||
| 93 | // *** EOF: Flag2ms() **************************************************************************** |
||
| 94 | |||
| 95 | |||
| 96 | |||
| 97 | |||
| 98 | // ********************************** EOF: timer.c ************************************************************************** |