XMEGA Timers

This timer library covers a large part of the ATXmega128A1U timer functionality. Since AVR timers differ quite a lot between chips, it is not possible to write universal functions for them. The described ATXmega128A1U functions are largely just primitive register read/write functions, but they are still more readable than raw registers.

• Timer clockSelection
  Timer 0/1 prescaler selection type. Possible values and meanings:
  • TC_CLKSEL_OFF_gc - Prescaler not used.
  • TC_CLKSEL_DIV1_gc - Prescale factor 1.
  • TC_CLKSEL_DIV2_gc - Prescale factor 2.
  • TC_CLKSEL_DIV4_gc - Prescale factor 4.
  • TC_CLKSEL_DIV8_gc - Prescale factor 8.
  • TC_CLKSEL_DIV64_gc - Prescale factor 64.
  • TC_CLKSEL_DIV256_gc - Prescale factor 256.
  • TC_CLKSEL_DIV1024_gc - Prescale factor 1024.

• Timer wgm
  Timer 0/1 mode. Possible values and meanings:
  • TC_WGMODE_NORMAL_gc - Normal mode
  • TC_WGMODE_FRQ_gc - Frequency generator mode
  • TC_WGMODE_SINGLESLOPE_gc - PWM mode, count up only
  • TC_WGMODE_DSTOP_gc - PWM mode, up/down count, registers updated at TOP
  • TC_WGMODE_DSBOTH_gc - PWM mode, up/down count, registers updated at TOP and BOTTOM
  • TC_WGMODE_DSBOTTOM_gc - PWM mode, up/down count, registers updated at BOTTOM

• Timer interrupt names and priorities.
  All interrupts on XMega series microcontrollers are prioritized.
• TC_OVFINTLVL - Overflow interrupt
  • _OFF_gc - Interrupt disabled
  • _LO_gc - Low priority interrupt
  • _MED_gc - Medium priority interrupt
  • _HI_gc - High priority interrupt
• TC_CCAINTLVL - Compare register interrupt
• TC_CCBINTLVL - Compare register interrupt
• TC_CCCINTLVL - Compare register interrupt
• TC_CCDINTLVL - Compare register interrupt
  • _OFF_gc - Interrupt disabled
  • _LO_gc - Low priority interrupt
  • _MED_gc - Medium priority interrupt
  • _HI_gc - High priority interrupt

• void TC0_ConfigClockSource( volatile TC0_t * tc, TC_CLKSEL_t clockSelection );
  Configure Timer0 clock source.
  • tc - Timer port
  • clockSelection - Clock setting
• void TC0_ConfigWGM( volatile TC0_t * tc, TC_WGMODE_t wgm );
  Configure Timer0 mode.
  • tc - Timer port
  • wgm - Mode setting
• void TC0_EnableCCChannels( volatile TC0_t * tc, uint8_t enableMask );
  Enable Timer0 signal generation units
  • tc - Timer port
  • enableMask - Channels to enable (multiple can be enabled with bitwise OR)
• void TC0_DisableCCChannels( volatile TC0_t * tc, uint8_t disableMask );
  Disable Timer0 signal generation units
  • tc - Timer port
  • disableMask - Channels to disable (multiple can be disabled with bitwise OR)
• void TC0_SetOverflowIntLevel( volatile TC0_t * tc, TC_OVFINTLVL_t intLevel );
  Enable Timer0 overflow interrupt
  • tc - Timer port
  • intLevel - Overflow interrupt priority
• void TC0_SetCCAIntLevel( volatile TC0_t * tc, TC_CCAINTLVL_t intLevel );
• void TC0_SetCCBIntLevel( volatile TC0_t * tc, TC_CCBINTLVL_t intLevel );
• void TC0_SetCCCIntLevel( volatile TC0_t * tc, TC_CCCINTLVL_t intLevel );
• void TC0_SetCCDIntLevel( volatile TC0_t * tc, TC_CCDINTLVL_t intLevel );
  

Timer0 signal generation channel A/B/C/D interrupt configuration

• tc - Timer port
• intLevel - Compare interrupt priority

• void TC0_Reset( volatile TC0_t * tc ); Timer0 reset
  • tc - Timer port

All functions apply similarly to Timer1.

• TC_SetCount( _tc, _count ) Allows changing the timer value manually
  • _tc - Timer module
  • _count - value to set
• TC_SetPeriod( _tc, _period ) Sets the timer period
  • _tc - Timer module
  • _period - period value
• TC_SetCompareA( _tc, _compareValue )
• TC_SetCompareB( _tc, _compareValue )
• TC_SetCompareC( _tc, _compareValue )
• TC_SetCompareD( _tc, _compareValue ) Set the compare value for a channel
  • _tc - Timer module
  • _compareValue - value to set
• TC_GetOverflowFlag( _tc ) Check overflow flag
  • _tc - Timer module
• TC_ClearOverflowFlag( _tc ) Clear overflow flag
  • _tc - Timer module
• TC_GetCCAFlag( _tc )
• TC_GetCCBFlag( _tc )
• TC_GetCCCFlag( _tc )
• TC_GetCCDFlag( _tc ) Check signal generator flag
  • _tc - Timer module
• TC_ClearCCAFlag( _tc )
• TC_ClearCCBFlag( _tc )
• TC_ClearCCCFlag( _tc )
• TC_ClearCCDFlag( _tc ) Clear signal generator flag
  • _tc - Timer module
• TC_GetCaptureA( _tc )
• TC_GetCaptureB( _tc )
• TC_GetCaptureC( _tc )
• TC_GetCaptureD( _tc ) Check event counter
  • _tc - Timer module

The example configures Port E Timer0 to normal counting mode and enables the overflow and compare channel A interrupts.

#include <homelab/xmega/clksys_driver.h>
 
#include <homelab/pin.h>
#include <homelab/xmega/TC_driver.h>
#include <avr/interrupt.h>
 
// Overflow interrupt
ISR(TCE0_OVF_vect)
{
	led_on(led_green);
}
 
// Compare channel A interrupt
ISR(TCE0_CCA_vect)
{
	led_off(led_green);
}
 
int main(void)
{
	// Configure green LED as output
	pin_setup_output(led_green);
	led_off(led_green);
 
	// Set Timer E0 period
	// Set Timer E0 duty cycle length
	TC_SetPeriod(&TCE0, 20000);							
	TC_SetCompareA(&TCE0, 15000);						
 
	// Set Timer E0 clock (F_CPU/1024)
	TC0_ConfigClockSource(&TCE0, TC_CLKSEL_DIV1024_gc);	
	// Set Timer E0 to normal mode
	TC0_ConfigWGM(&TCE0, TC_WGMODE_NORMAL_gc);			
 
	// Enable overflow interrupt with high priority
	// Enable compare channel A interrupt with medium priority
	TC0_SetOverflowIntLevel(&TCE0,TC_OVFINTLVL_HI_gc);	
	TC0_SetCCAIntLevel(&TCE0, TC_CCAINTLVL_MED_gc);		
 
	// Enable medium and high priority interrupts
	// Enable global interrupts
	PMIC.CTRL |= PMIC_MEDLVLEN_bm|PMIC_HILVLEN_bm;
	sei();												
 
	// Empty loop, program runs on interrupts
	while(1);
}