CODEWITHSUNDEEP
cportbit8051sdcc
RassK
RassK

Reputation: 490

8051 Controller port bit reading / writing

The idea is to read any bit from a port. Anyway accessing to one known bit is simple, like 

P0_0 <-- gets bit 0 from port 0

But if i need to access bit y via function?

read_bit(__bit y){
    return P0_y; // <-- just an idea but its not right becouse of syntax.
}

using SDCC to program and 8051 header.

Upvotes: 0

Views: 1966

Answers (3)

rajesh6115
rajesh6115

Reputation: 735

just see this function

char chek_bit_p0(unsigned char chk_bit){
 if((P0>>chk_bit) & 1)
    return 1;
 else 
    return 0;
}

or simply by a macro like below (preferred way)

#define chek_bit_p0(x) (((P0>>x)&1)&&1)

Upvotes: 0

Alexey Frunze
Alexey Frunze

Reputation: 62048

If it's a literal constant, you can use a macro trick:

#define READ_P0_BIT(BIT) (P0_ ## BIT)
unsigned x = READ_P0_BIT(1);

If it's not a literal constant, you can do this:

int readP0bit(int bitNo)
{
    switch (bitNo)
    {
    case 0: return P0_0;
    case 1: return P0_1;
    // ...
    case 7: return P0_7;
    default: return 0;
    }
}

Upvotes: 1

Some programmer dude
Some programmer dude

Reputation: 409166

You can make a local array-variable that contains the bits in the function, and use the "bit" as an index into this array.

Something like:

__bit read_bit(const int b)
{
    __bit all_bits[8] = {
        P0_0,
        P0_1,
        /* etc. */
        P0_7
    };

    return (b < 8 ? all_bits[b] : 0);
}

Upvotes: 0

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