help on avr programming - problem with C syntax

[mehipour]

avr pinb

hi folks,

I programming AVR ATmega32 for an embedded web-server. There's this C language Syntax that I have confronted and I don't understand.

(PINB &(1<<PB2)) == 0)

I didn't fully understand the meaning of this syntax. I suppose that PINB is the portb register and PB2 is the third bit of this port which is used as an interrupt.
thanks a lot,

Mehipour

 

[wek]

help on avr programming

PINB and PB2 are macros. In some of the header files you are including, there are definitions for PINB and PB2; for example, if you are using avr-gcc, you are including iom32.h (via io.h), which contains:

#define PINB _SFR_IO8(0x16)

and

#define PB2 2


JW

 

[ecnbom]

help on avr programming

Hi mehipour:
I think the whole word is
" if (PINB &(1<<PB2)) == 0) "
it means if PB2 is equal to 0(PB2 is low).
In ICCAVR, to get a status of a IO(eg.PB2), you can read register PINX(eg.PINB), but the value consist of all PINX(8 bits), so you must dispose of some bits, "&(1<<PB2)" is used for that job.