I2C silly addressing question -P.S.
Being paranoid, I'm already using 10k resistors to each SDA/SCL
line. Is this necessary (or even just prudent?).
--- In basicstamps@y..., "ghidera2000" <ghidera2000@y...> wrote:
> I need to use 2 I2C chips at once (finally) but I can't seem to
find
> any description on how to set the addresses!
>
> All examples I've seen are single chip and all set the three
address
> pins low. I'm assuming I'd use a pullup resistor (say 10k) on A0
and
> ground the other two to give a chip address of "1" but, A1 for an
> address of "2" and A0+A1 for 3, etc. I'm a bit leary about frying
a
> chip though so can anyone confirm this for me?
>
> Signed Chicken Little.
line. Is this necessary (or even just prudent?).
--- In basicstamps@y..., "ghidera2000" <ghidera2000@y...> wrote:
> I need to use 2 I2C chips at once (finally) but I can't seem to
find
> any description on how to set the addresses!
>
> All examples I've seen are single chip and all set the three
address
> pins low. I'm assuming I'd use a pullup resistor (say 10k) on A0
and
> ground the other two to give a chip address of "1" but, A1 for an
> address of "2" and A0+A1 for 3, etc. I'm a bit leary about frying
a
> chip though so can anyone confirm this for me?
>
> Signed Chicken Little.
Comments
Using pull up termination resistors is not being
paranoid, it's necessary for i2c. The spec for i2c
does call for active or passive termination as the
clock and data signals are active low. In addition,
the i2c bus is a daisy chain bus which does need
termination to function properly. This termination is
generally applied to the ends of a circuit similar how
we used to wire 10Base2 (RG-58 coax) networks
together. As such, one cannot apply a termination
network to each i2c transceiver/node as this will
distort/degrade the (clock and data) signal quality
down the ends of the bus.
10K is a good value. It really depends upon the drive
characteristics of the transceivers.
As far as addressing the i2c transceivers, it depends
on what is specified by the manufacturer. I have had
it done by a pull up or pull down network for each
transceiver to be read in as part of the device
initialization. Again, it depends on the manufacturer.
kevin
KC6POB
--- ghidera2000 <ghidera2000@y...> wrote:
> Being paranoid, I'm already using 10k resistors to
> each SDA/SCL
> line. Is this necessary (or even just prudent?).
>
> --- In basicstamps@y..., "ghidera2000"
> <ghidera2000@y...> wrote:
> > I need to use 2 I2C chips at once (finally) but I
> can't seem to
> find
> > any description on how to set the addresses!
> >
> > All examples I've seen are single chip and all set
> the three
> address
> > pins low. I'm assuming I'd use a pullup resistor
> (say 10k) on A0
> and
> > ground the other two to give a chip address of "1"
> but, A1 for an
> > address of "2" and A0+A1 for 3, etc. I'm a bit
> leary about frying
> a
> > chip though so can anyone confirm this for me?
> >
> > Signed Chicken Little.
>
>
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