Thread: How to read one bit at one time

I'm not really sure what you want to do, but maybe the program below will give you an idea (?)

Code:

#include <stdio.h>
#include <limits.h>

int main(void)
{
    const unsigned char testbyte = 100;
    int i;
    
    for (i = CHAR_BIT - 1; i >= 0; --i) {
        if ((testbyte & 1 << i) != 0)
            printf("1");
        else
            printf("0");
    }
    printf("\n");
    
    return 0;
}

Edit: If you want to go from LS bit to MS bit, which it seems you want to, then the following is probably better

Code:

#include <stdio.h>
#include <limits.h>

int main(void)
{
    const unsigned char testbyte = 100;
    int i;
    
    for (i = 0; i < CHAR_BIT; ++i) {
        if ((testbyte & 1 << i) != 0)
            printf("1");
        else
            printf("0");
    }
    printf("\n");
    
    return 0;
}

Actually, maybe I see what you mean now. Examine

Code:

#include <stdio.h>
#include <limits.h>

const unsigned char pin1 = 165;

int getPin1(int pos)
{
    return (pin1 & (1 << pos)) != 0;
}

int main(void)
{
    unsigned result = 0;
    int i;
    
    for (i = 0; i < CHAR_BIT; ++i) {
        int b = getPin1(i);        
        result |= b << i;
    }
    printf("result (hex) = 0x%x\n", result);
    
    return 0;
}

getPin1() is obviously a made up function to get the bits as you describe, but the rest probably (?) does what you want

Originally Posted by Hodor

I have no way to check this

I2C implementation on 8051 microcontroller

Code:

unsigned char  I2CRead () 
{ 
     unsigned char  i , Data = 0 ; 
     for ( i  = 0 ;  i  < 8 ;  i ++) { 
        SCL  = 1 ; 
         if ( SDA ) 
             Data |= 1 ; 
         if ( i < 7 ) 
             Data <<= 1 ; 
        SCL  = 0 ; 
     } 
     return Data ; 
}

Does this function read bit one by one

Yes it does.

Code:

         if ( SDA ) 
             Data |= 1 ;

This is the 1-bit-at-a-time code.

Since it goes round the loop 8 times, it collects 8 single bits, and puts them into a byte.

This is simpler.

Code:

unsigned char  I2CRead () 
{ 
     unsigned char  i , Data = 0 ; 
     for ( i  = 0 ;  i  < 8 ;  i ++) { 
        SCL  = 1 ; 
          Data <<= 1 ;
          if ( SDA ) 
             Data |= 1 ; 
        SCL  = 0 ; 
     } 
     return Data ; 
}