timer_xmega.c

Go to the documentation of this file.

#include <drv/timer_xmega.h>
#include <cfg/macros.h> // BV()

#include <cpu/types.h>
#include <cpu/irq.h>

#include <avr/io.h>

/* Helper MACROS taken from the Atmel examples and altered
 *
 *  The AVR XMEGA has different structures for TC0 and TC1,
 *  however these only differ in the amount of compare/capture
 *  channels, so for this purpose they can be used exactly the same
  */

//check if the bitvalues of the TC0 and TC1 Timer/Counters are really the same
#if TC0_CLKSEL_gm != TC1_CLKSEL_gm || TC0_WGMODE_gm != TC1_WGMODE_gm || TC0_OVFINTLVL_gm != TC1_OVFINTLVL_gm
    #error TC0 and TC1 Timer/Counters cannot be configured with the same bitvalues
#endif

#define TIMER_CONFIG_CLOCK_SOURCE(_clkSel)\
    ((TIMERCOUNTER).CTRLA = ((TIMERCOUNTER).CTRLA & ~TC0_CLKSEL_gm) | _clkSel)

#define TIMER_CLEAR_FLAGS() ((TIMERCOUNTER).INTFLAGS = 0xFF)

#define TIMER_SET_PERIOD( _period ) ( (TIMERCOUNTER).PER = (_period) )

#define TIMER_SET_OVERFLOW_INTERRUPT_LEVEL( _interruptLevel )\
    ((TIMERCOUNTER).INTCTRLA = ( (TIMERCOUNTER).INTCTRLA & ~TC0_OVFINTLVL_gm ) | _interruptLevel)

#define TIMER_CONFIG_WGM(_wgm)\
    ((TIMERCOUNTER).CTRLB = ( (TIMERCOUNTER).CTRLB & ~TC0_WGMODE_gm ) | _wgm)

#define TIMER_RESET() ( (TIMERCOUNTER).CTRLFSET = TC_CMD_RESET_gc )

//Define TIMER_PRESCALE_REG_VALUE bases on the provided
//TIMER_PRESCALER value
#if TIMER_PRESCALER == 0
    #define TIMER_CLKSEL_gc             TC_CLKSEL_OFF_gc
#elif TIMER_PRESCALER == 1
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV1_gc
#elif TIMER_PRESCALER == 2
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV2_gc
#elif TIMER_PRESCALER == 4
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV4_gc
#elif TIMER_PRESCALER == 16
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV16_gc
#elif TIMER_PRESCALER == 64
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV64_gc
#elif TIMER_PRESCALER == 256
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV256_gc
#elif TIMER_PRESCALER == 1024
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV1024_gc
#else
    #error Invalid value for TIMER_PRESCALER has been defined! Using default of 1
    #define TIMER_CLKSEL_gc             TC_CLKSEL_DIV1_gc
#endif

void timer_hw_init(void)
{
    //Save and disable IRQ
    cpu_flags_t flags;
    IRQ_SAVE_DISABLE(flags);
    //disable the timer
    TIMER_CONFIG_CLOCK_SOURCE(TC_CLKSEL_OFF_gc);
    //clear all flags
    TIMER_CLEAR_FLAGS();
    //setup the Periode register value
    //CNT register will be reset to 0 when CNT == PER
    TIMER_SET_PERIOD(TIMER_PERIOD_VALUE);
    //set the Waveform Generation Mode to Normal
    TIMER_CONFIG_WGM(TC_WGMODE_NORMAL_gc);
    //enable the overflow interrupt
    //use the highest priority
    TIMER_SET_OVERFLOW_INTERRUPT_LEVEL(TC_OVFINTLVL_HI_gc);
    //enable timer by setting the correct prescaler/clock
    TIMER_CONFIG_CLOCK_SOURCE(TIMER_CLKSEL_gc);
    //Restore IRQ
    IRQ_RESTORE(flags);
}