OpenModem/bertos/cpu/avr/drv/timer_xmega.c

/**
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 *
 * \author Onno <developer@gorgoz.org>
 *
 * \brief Low-level timer module for AVR XMEGA (implementation).
 *
 * This file is heavily inspired by the AVR implementation for BeRTOS,
 * but uses a different approach for implementing the different debug
 * ports, by using the timer structs.
 *
 * This module is automatically included so no need to include
 * in test list.
 * notest: all
 */

#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);
}