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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 60 | jimmy | 1 | /** |
| 2 | * Timebase software module. Utilizes timer0 to provide a 32bit timebase with |
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| 3 | * millisecond-granularity to the application. |
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| 4 | * |
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| 5 | * @target ATmega8 |
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| 6 | * |
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| 7 | * @author Martin Thomas |
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| 8 | * @author Jimmy Myhrman |
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| 9 | * |
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| 127 | jimmy | 10 | * @date 2006-11-19 |
| 60 | jimmy | 11 | */ |
| 12 | |||
| 13 | /*----------------------------------------------------------------------------- |
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| 14 | * Includes |
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| 15 | *---------------------------------------------------------------------------*/ |
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| 16 | #include <inttypes.h> |
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| 17 | #include <avr/io.h> |
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| 18 | #include <avr/interrupt.h> |
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| 19 | |||
| 20 | #include <timebase.h> |
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| 21 | |||
| 22 | |||
| 23 | /*----------------------------------------------------------------------------- |
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| 24 | * Globals |
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| 25 | *---------------------------------------------------------------------------*/ |
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| 26 | volatile uint32_t gMilliSecTick; |
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| 27 | |||
| 28 | |||
| 29 | /*----------------------------------------------------------------------------- |
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| 30 | * Interrupt Service Routines |
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| 31 | *---------------------------------------------------------------------------*/ |
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| 32 | ISR(SIG_OVERFLOW0) { |
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| 33 | TCNT0 = TIMEBASE_RELOAD; |
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| 34 | gMilliSecTick++; |
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| 35 | } |
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| 36 | |||
| 37 | |||
| 38 | /*----------------------------------------------------------------------------- |
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| 39 | * Public Functions |
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| 40 | *---------------------------------------------------------------------------*/ |
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| 41 | /** |
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| 42 | * Initializes the timebase. The hardware timer interrupt source will be |
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| 43 | * enabled, but global interrupts need to be enabled by the application. |
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| 44 | */ |
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| 127 | jimmy | 45 | void Timebase_Init() { |
| 60 | jimmy | 46 | TCCR0 = (1<<CS01) | (1<<CS00); // prescaler: 64 |
| 47 | TCNT0 = TIMEBASE_RELOAD; // set initial reload-value |
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| 48 | TIFR |= (1<<TOV0); // clear overflow int. |
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| 49 | TIMSK |= (1<<TOIE0); // enable overflow-interrupt |
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| 50 | } |
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| 51 | |||
| 52 | /** |
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| 53 | * Reads the current time. |
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| 54 | * |
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| 55 | * @return |
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| 56 | * The current time in milliseconds (32bit value). |
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| 57 | */ |
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| 127 | jimmy | 58 | uint32_t Timebase_CurrentTime(void) { |
| 60 | jimmy | 59 | uint8_t sreg; |
| 60 | uint16_t res; |
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| 61 | sreg=SREG; |
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| 62 | cli(); |
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| 63 | res = gMilliSecTick; |
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| 64 | SREG=sreg; |
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| 65 | return res; |
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| 66 | } |
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| 67 | |||
| 68 | /** |
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| 69 | * Checks how much time has passed since a given timestamp. |
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| 70 | * |
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| 71 | * @param t0 |
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| 72 | * The timestamp. |
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| 73 | * @return |
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| 74 | * Number of milliseconds that have passed since t0. |
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| 75 | */ |
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| 127 | jimmy | 76 | uint32_t Timebase_PassedTimeMillis(uint32_t t0) { |
| 60 | jimmy | 77 | uint8_t sreg; |
| 78 | uint16_t res; |
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| 79 | sreg=SREG; |
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| 80 | cli(); |
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| 81 | res = (uint16_t)(gMilliSecTick-t0); |
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| 82 | SREG=sreg; |
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| 83 | return res; |
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| 84 | } |