Define Macros to SET and CLEAR bit of a PIN in C

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mahmoud2506

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2022-05-04

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Define Macros to SET and CLEAR bit of a PIN in C

Given a PIN (value in HEX) and bit number, we have to SET and then CLEAR given bit of the PIN (val) by using Macros.

Macros definitions:

    #define SET(PIN,N) (PIN |=  (1<<N))
    #define CLR(PIN,N) (PIN &= ~(1<<N))

Here,

SET and CLR are the Macro names
PIN is the value whose bit to set or/and clear
N is the bit number to set or/and clear

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mahmoud2506

2022-05-04

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Example:

#include <stdio.h>

#define SET(PIN,N) (PIN |=  (1<<N))
#define CLR(PIN,N) (PIN &= ~(1<<N))

int main(){
	
	unsigned char val = 0x11;
	unsigned char bit = 2;
	
	printf("val = %X\n",val);
	
	//set  bit 2 of val
	SET(val,bit);
	printf("Aftre setting  bit %d, val = %X\n", bit, val);

	//clear bit 2 of val
	CLR(val,bit);
	printf("Aftre clearing bit %d, val = %X\n", bit, val);	
	
	return 0;	
}

Output

    val = 11
    Aftre setting  bit 2, val = 15
    Aftre clearing bit 2, val = 11

Explanation:

Initially val is 0x11, its binary value is "0001 0001".
In the example, we are setting and clear bit 2 (please note start counting bits from 0 i.e. first bit is 0, second bit is 1 and third bit is 2).
After calling Macro SET(val,bit), the bit number 2 (i.e. third bit) will be set/hight and the value of val will be "0001 0101" that will be 0x15 in Hexadecimal.
And then, we are calling CLR(val,bit), after calling this Macro, the bit number 2 (i.e. third bit) will be cleared and the value of val will be "0001 0001" again, that is 0x11 in Hexadecimal.