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How can I bit access to pin of port?

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alvrAVR

Posted: Mar 15, 2012 - 02:17 PM

Joined: Mar 15, 2012
Posts: 31

Hello,
I am beginer with AVR (I know only C51 and Keil IDE).
How can I use bit access to pin of port and define name of this pin? When I use access to whole port (as you see in first example) it is OK, but can I read and write only to pin (second example)?

example with port access is OK:

#define INPORT PORTA
#define OUTPORT PORTB

int main() {
DDRA = 0;//set to input
DDRB = 255;//set to output
OUTPORT = INPORT;//reading PORTA and writing to PORTB is OK
}

example with pin access:

#define INPIN PORTA4
#define OUTPIN PORTB4

int main() {
DDRA = 0;//set to input
DDRB = 255;//set to output
OUTPIN = INPIN;//reading PIN and writing to PIN it can not compile ??
PORTB5 = 1;//even it can not compile ??
}

Please, what is simply corect way for read and write pin and define his name?
Thank you very much and aI am sorry for my bad english..

miltronik

Posted: Mar 15, 2012 - 02:30 PM

Joined: Feb 10, 2005
Posts: 54

Use this:

H-File:

Code:

typedef struct

{

    unsigned char   bit0 : 1;

    unsigned char   bit1 : 1;

    unsigned char   bit2 : 1;

    unsigned char   bit3 : 1;

    unsigned char   bit4 : 1;

    unsigned char   bit5 : 1;

    unsigned char   bit6 : 1;

    unsigned char   bit7 : 1;

} bit_field;

#define GET_BITFIELD( addr )    ( *(( volatile bit_field * ) (addr)) )

// make your define for the Port-Pin:

#define Your_Port_PIN GET_BITFIELD ( &PORTF ).bit4

// example: PORTF Bit 4 (output)

Than access your Bit with:

Code:

Your_Port_PIN = 1;

OR

Your_Port_PIN = 0;

The same with Inputs:

#define clock_input GET_BITFIELD ( &PINB ).bit6

clawson

Posted: Mar 15, 2012 - 03:48 PM

Joined: Jul 18, 2005
Posts: 62348
Location: (using avr-gcc in) Finchingfield, Essex, England

To add to what Mitronik says. See these two tutorials:

Bit manipulation 101
(this includes sbit.h on page 6 which expands on what Mitronik presented)

How to define a pin as a variable
(which focuses on the use of "bitfields" in a struct)

_________________

alvrAVR

Posted: Mar 15, 2012 - 04:43 PM

Joined: Mar 15, 2012
Posts: 31

Thank you very much. Now it already run. And I will look on added tutorials.
May be I will ask you with other problem later.... Smile

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