-----Original Message-----
From:   Roberto Fonseca Iannini [SMTP:roberto1@LINKEXPRESS.COM.BR]
Sent:   Friday, November 12, 1999 12:06 AM
To:     PICLIST@MITVMA.MIT.EDU
Subject:        reading indivivual bits in a byte var

I have a byte that came from serial port and I need to make decisions
based in individual bits of it and then take several attitudes like set
a led, etc...
Example: A byte called CONTROL is formed by: 0b11001101
The bit0 defines if an led must be set or turned off;
Bit1 and bit2 defines if an motor will run or not;
Bit4 defines clockwise or counterclockwise;
and so on...
The whole code is working, but I need some tips about how to read a
single bit inside a byte variable (in c language).
I was thinking in "is.flag"... but I didn't know how to implement it.
All ideas are welcome.

See you,

Roberto

You can use a union to map bit variables onto a byte variable.

union bitvars
{
        unsigned char byte;
        struct
        {
                unsigned     bit0:1;
                unsigned     bit1:1;
                unsigned     bit2:1;
                unsigned     bit3:1;
                unsigned     bit4:1;
                unsigned     bit5:1;
                unsigned     bit6:1;
                unsigned     bit7:1;
        } bits;
}

union bitvars control;
control.byte = 0xAA;    /* use the variable as an unsigned char */

if(control.bits.bit0 == 0)      /* or access the bits individually */
{
}
etc...etc...

Regards

Mike Rigby-Jones

.