Re: [Sdcc-user] Setting up and sending serial messages

[Gernot F. <g....@gm...>]

On Wed, 22 Jun 2005, Jean-Paul wrote:
> >
> > Or a bit expansive use a PCF8574 IIC-Portexpander. This use 2 pins.
> > You get 8 bidirektional portpins. One or 2 of them are free after =20
> > connecting the
> > Display.
> >
>=20
> You get for the same price an interrupt capability on all eight pins!
> Use that only if you really need in/out pins. The I2C overhead could be=
 =20
> too big for the 2 or 4K flash (89C4051).

You can have basic iic in 129 Bytes


extern bit writeok;

void iic_delay(void)
{
=09_asm nop _endasm;
=09_asm nop _endasm;
=09_asm nop _endasm;
=09_asm nop _endasm;
}
void iic_start(void)
{
=09_asm setb scl _endasm;
=09iic_delay();
=09_asm clr sda  _endasm;
        iic_delay();
}
void iic_stop(void)
{
=09_asm clr sda _endasm;
        iic_delay();
=09_asm setb scl _endasm;
        iic_delay();
=09_asm setb sda _endasm;
        iic_delay();
}
void iic_putc(unsigned char c)
{
=09c=3Dc;
=09_asm=20
=09mov a,dpl
=09mov dpl,#8
=09$00021:
=09=09clr scl
=09=09lcall _iic_delay
=09=09rlc a
=09=09mov sda,c
        =09lcall _iic_delay
=09=09setb scl
        =09lcall _iic_delay
=09djnz dpl,$00021
=09clr scl
        lcall _iic_delay
=09setb sda
        lcall _iic_delay
=09mov c,sda
=09cpl c
=09mov _writeok,c
=09setb scl
        lcall _iic_delay
=09clr scl
        lcall _iic_delay
=09_endasm;
}

unsigned char iic_getc(bit last)
{
=09last&=3D255;
=09_asm=09
=09push dpl
=09mov dpl,#8
=09$00022:=09
=09=09mov c,sda
=09=09rlc a=09
=09=09setb scl
=09       =09 lcall _iic_delay
=09=09clr scl
        =09lcall _iic_delay
=09djnz dpl,$00022

=09mov b,a
=09pop acc
=09mov c,acc.0
=09mov sda,c
       =09lcall _iic_delay
=09setb scl
       =09lcall _iic_delay
=09clr scl
       =09lcall _iic_delay
=09setb sda
       =09lcall _iic_delay
=09_endasm;
=09return B;
}


--=20
MFG Gernot