> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
> Of PICdude
> Sent: 13 February 2012 02:20
> To: piclist@mit.edu
> Subject: Re: [PIC] Bit operations in C -- shift?
>=20
> Ack!!  I meant 70 *BITS* (hence my use of 9 bytes in assembly to hold
> the data).  I see replies, so will get to them in a couple hours when
> I get home.
>=20
> Cheers,
> -Neil

70 bits is more manageable, but even in this case shifting all those bytes =
is inefficient unless you actually NEED to shift them (e.g. some kind of LF=
SR).  If you simply need to spit these out as a serial stream then using a =
bit mask which you shift 8 times and then move onto the next byte makes far=
 more sense.

Something like this should do it, and would be very simple to modify should=
 you ever need to send a variable number of bits etc.

#define BIT_ARRAY_SIZE 70

void ShiftOut( uint8_t *buff )
{
    uint8_t bitcount =3D BIT_ARRAY_SIZE + 1;
    uint8_t bitmask =3D 0x01;

    while( bitcount-- )
    {
        if( bitmask & *buff )
        {
            SendHiBit();
        }
        else
        {
            SendLowBit();
        }

        /* Move to next bit to send */
        bitmask <<=3D 1;

        /* If bit mask is zero we need to move to the next byte */
        if( bitmask =3D=3D 0 )
        {
            bitmask=3D 0x01;
            buff++;
        }
    }
}

Cheers

Mike

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--=20
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