/************************************************************************** * * Copyright (C) 2009 Steve Karg * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sublicense, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be included * in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. *********************************************************************/ #include #include #include "hardware.h" #include "timer.h" #ifndef F_CPU #error "F_CPU must be defined for Timer configuration." #endif /* Timer2 Prescaling: 1, 8, 32, 64, 128, 256, or 1024 */ #define TIMER_MICROSECONDS 1000UL #define TIMER_TICKS(p) \ (((((F_CPU)/(p))/1000UL) \ *(TIMER_MICROSECONDS))/1000UL) #define TIMER_TICKS_MAX 255UL /* adjust the prescaler for the processor clock */ #if (TIMER_TICKS(1) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 1 #elif (TIMER_TICKS(8) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 8 #elif (TIMER_TICKS(32) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 32 #elif (TIMER_TICKS(64) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 64 #elif (TIMER_TICKS(128) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 128 #elif (TIMER_TICKS(256) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 256 #elif (TIMER_TICKS(1024) <= TIMER_TICKS_MAX) #define TIMER2_PRESCALER 1024 #else #error "TIMER2: F_CPU too large for timer prescaler." #endif #define TIMER2_TICKS TIMER_TICKS(TIMER2_PRESCALER) /* Timer counts up from count to TIMER_TICKS_MAX and then signals overflow */ #define TIMER2_COUNT (TIMER_TICKS_MAX-TIMER2_TICKS) /* counter for the the timer which wraps every 49.7 days */ static volatile uint32_t Millisecond_Counter; static volatile uint8_t Millisecond_Counter_Byte; /************************************************************************* * Description: Timer Interrupt Handler * Returns: nothing * Notes: none *************************************************************************/ static inline void timer_interrupt_handler( void) { /* Set the counter for the next interrupt */ TCNT2 = TIMER2_COUNT; Millisecond_Counter++; Millisecond_Counter_Byte++; } /************************************************************************* * Description: Timer Interrupt Service Routine - Timer Overflowed! * Returns: none * Notes: Global interupts must be enabled *************************************************************************/ ISR(TIMER2_OVF_vect) { timer_interrupt_handler(); } /************************************************************************* * Description: returns the current millisecond count * Returns: none * Notes: This method only disables the timer overflow interrupt. *************************************************************************/ uint32_t timer_milliseconds( void) { uint32_t timer_value; /* return value */ /* Disable the overflow interrupt. Prevents value corruption that would happen if interrupted */ BIT_CLEAR(TIMSK2, TOIE2); timer_value = Millisecond_Counter; /* Enable the overflow interrupt */ BIT_SET(TIMSK2, TOIE2); return timer_value; } /************************************************************************* * Description: returns the current millisecond count * Returns: none * Notes: This method only disables the timer overflow interrupt. *************************************************************************/ uint8_t timer_milliseconds_byte( void) { return Millisecond_Counter; } /************************************************************************* * Description: Initialization for Timer * Returns: none * Notes: none *************************************************************************/ void timer_init( void) { /* Normal Operation */ TCCR2A = 0; /* Timer2: prescale selections: CSn2 CSn1 CSn0 Description ---- ---- ---- ----------- 0 0 0 No Clock Source 0 0 1 No prescaling 0 1 0 CLKt2s/8 0 1 1 CLKt2s/32 1 0 0 CLKt2s/64 1 0 1 CLKt2s/128 1 1 0 CLKt2s/256 1 1 1 CLKt2s/1024 */ #if (TIMER2_PRESCALER==1) TCCR2B = _BV(CS20); #elif (TIMER2_PRESCALER==8) TCCR2B = _BV(CS21); #elif (TIMER2_PRESCALER==32) TCCR2B = _BV(CS21) | _BV(CS20); #elif (TIMER2_PRESCALER==64) TCCR2B = _BV(CS22); #elif (TIMER2_PRESCALER==128) TCCR2B = _BV(CS22) | _BV(CS20); #elif (TIMER2_PRESCALER==256) TCCR2B = _BV(CS22) | _BV(CS21); #elif (TIMER2_PRESCALER==1024) TCCR2B = _BV(CS22) | _BV(CS21) | _BV(CS20); #else #error Timer2 Prescale: Invalid Value #endif /* Clear any TOV Flag set when the timer overflowed - by setting! */ BIT_SET(TIFR2, TOV2); /* Initial value */ TCNT2 = TIMER2_COUNT; /* Enable the overflow interrupt */ BIT_SET(TIMSK2, TOIE2); power_timer2_enable(); }