Allowing specific system-wide interrupts

In addition to globally enabling interrupts, each device's particular interrupt needs to be enabled separately if interrupts for this device are desired. While some devices maintain their interrupt enable bit inside the device's register set, external and timer interrupts have system-wide configuration registers.

Example:

// Enable timer 1 overflow interrupts.
timer_enable_int(_BV(TOIE1));
// Do some work...
// Disable all timer interrupts.
timer_enable_int(0);

Note:

static __inline__ void timer_enable_int (unsigned char ints)
#define enable_external_int(mask) (__EICR = mask)
#define INTERRUPT(signame)
#define __INTR_ATTRS used

Obsolete IO macros

Back in a time when AVR-GCC and avr-libc could not handle IO port access in the direct assignment form as they are handled now, all IO port access had to be done through specific macros that eventually resulted in inline assembly instructions performing the desired action.

These macros became obsolete, as reading and writing IO ports can be done by simply using the IO port name in an expression, and all bit manipulation (including those on IO ports) can be done using generic C bit manipulation operators.

The macros in this group simulate the historical behaviour. While they are supposed to be applied to IO ports, the emulation actually uses standard C methods, so they could be applied to arbitrary memory locations as well.
#define inp(port) (port)
#define outp(val, port) (port) = (val)
#define inb(port) (port)
#define outb(port, val) (port) = (val)
#define sbi(port, bit) (port) |= (1 << (bit))
#define cbi(port, bit) (port) &= ~(1 << (bit))

#define cbi(port, bit) (port) &= ~(1 << (bit))

Deprecated

Clear bit in IO port port.

#define enable_external_int(mask) (__EICR = mask)

Deprecated

This macro gives access to the GIMSK register (or EIMSK register if using an AVR Mega device or GICR register for others). Although this macro is essentially the same as assigning to the register, it does adapt slightly to the type of device being used. This macro is unavailable if none of the registers listed above are defined.

#define inb(port) (port)

Deprecated

Read a value from an IO port port.

#define inp(port) (port)

Deprecated

Read a value from an IO port port.

#define INTERRUPT(signame)

Value:

void signame (void) __attribute__ ((interrupt,__INTR_ATTRS));  void signame (void)

Deprecated

Introduces an interrupt handler function that runs with global interrupts initially enabled. This allows interrupt handlers to be interrupted.

As this macro has been used by too many unsuspecting people in the past, it has been deprecated, and will be removed in a future version of the library. Users who want to legitimately re-enable interrupts in their interrupt handlers as quickly as possible are encouraged to explicitly declare their handlers as described above.

#define outb(port, val) (port) = (val)

Deprecated

Write val to IO port port.

#define outp(val, port) (port) = (val)

Deprecated

Write val to IO port port.

#define sbi(port, bit) (port) |= (1 << (bit))

Deprecated

Set bit in IO port port.

static __inline__ void timer_enable_int (unsigned char ints) [static]

Deprecated

This function modifies the timsk register. The value you pass via ints is device specific.