MEAM.Design - ATmega32 Programming - Interrupts
To support interrupts on the ATmega32, you must include <avr/interrupt.h>, which is included by default in m_general.h or teensy_general.h file.
To then enable global interrupts, call the function sei();. To disable global interrupts, call the function cli();.
To service an interrupt, you must write a separate function within your C file according to the following syntax:
ISR(SOURCE_vect){...}
where SOURCE corresponds to one of the sources listed below:
| INT0_vect | External Interrupt Request 0 |
| INT1_vect | External Interrupt Request 1 |
| INT2_vect | External Interrupt Request 2 |
| INT3_vect | External Interrupt Request 3 |
| INT6_vect | External Interrupt Request 6 |
| PCINT0_vect | Pin Change Interrupt Request 0 (from PCINT0 through PCINT7) |
| TIMER1_CAPT_vect | Timer/Counter1 Capture Event |
| TIMER1_COMPA_vect | Timer/Counter1 Compare Match A |
| TIMER1_COMPB_vect | Timer/Counter1 Compare Match B |
| TIMER1_COMPC_vect | Timer/Counter1 Compare Match C |
| TIMER1_OVF_vect | Timer/Counter1 Overflow |
| TIMER0_COMPA_vect | Timer/Counter0 Compare Match A |
| TIMER0_COMPB_vect | Timer/Counter0 Compare Match B |
| TIMER0_OVF_vect | Timer/Counter0 Overflow |
| SPI_STC_vect | SPI Serial Transfer Complete |
| USART1_RX_vect | USART1, Rx Complete |
| USART1_UDRE_vect | USART1 Data register Empty |
| USART1_TX_vect | USART1, Tx Complete |
| ANALOG_COMP_vect | Analog Comparator |
| ADC_vect | ADC Conversion Complete |
| EE_READY_vect | EEPROM Ready |
| TIMER3_CAPT_vect | Timer/Counter3 Capture Event |
| TIMER3_COMPA_vect | Timer/Counter3 Compare Match A |
| TIMER3_COMPB_vect | Timer/Counter3 Compare Match B |
| TIMER3_COMPC_vect | Timer/Counter3 Compare Match C |
| TIMER3_OVF_vect | Timer/Counter3 Overflow |
| TWI_vect | 2-wire Serial Interface |
| SPM_READY_vect | Store Program Memory Read |
| TIMER4_COMPA_vect | Timer/Counter4 Compare Match A |
| TIMER4_COMPB_vect | Timer/Counter4 Compare Match B |
| TIMER4_COMPD_vect | Timer/Counter4 Compare Match D |
| TIMER4_OVF_vect | Timer/Counter4 Overflow |
| TIMER4_FPF_vect | Timer/Counter4 Fault Protection Interrupt |
Important Note from the AVR-LIBC FAQ.
My program doesn't recognize a variable updated within an interrupt routine?
When using the optimizer, in a loop like the following one:
uint8_t flag;...ISR(SOME_vect) {
flag = 1;
}...
while (flag == 0) {...}
the compiler will typically access flag only once, and optimize further accesses completely away, since its code path analysis shows that nothing inside the loop could change the value of flag anyway. To tell the compiler that this variable could be changed outside the scope of its code path analysis (e. g. from within an interrupt routine), the variable needs to be declared like:
volatile uint8_t flag;
In other words, sometimes the compile optimizer will "outsmart" you and hard code a variable that it doesn't realize is used elsewhere. So if you want to use a global variable outside of your interrupt handler (e.g. in your main function), you will probably have to declare the variable as volatile.