I concur, Olin.

The only time I2C needs series limiting resistors is when the bus goes 
between PCBs or if the
PCB itself is HUGE. The speed of transfer is simply too slow and too 
self-limiting to need spike
suppression. Adding extra parts is a problem of inventory, etc that adds up.

I might add that the I2C spec was designed for the original application: 
interconnecting TV/VCR
/Audio circuits on different PCBs together neatly, reducing the 
complexity of the PCBs and the
connector size. The present-day use is similar but never has many nodes.

--Bob

Olin Lathrop wrote:

>Ken Pergola wrote:
>  
>
>>Actually, a series protection resistors for the I2C device positioned
>>as follows is a very good practice to implement in I2C designs:
>>
>>               VCC
>>                \
>>                / Rp
>>                \
>>                /
>>                |            Rs
>>PIC-------------|------/\/\/\/\/\/\-----X24C02
>>
>>This practice is detailed in the I2C specification and makes a more
>>robust design, which is probably why the original poster has the
>>series resistors in there. An extra series resistor for the SDA and
>>SCL lines on every I2C slave device is just very cheap insurance to
>>have.
>>    
>>
>
>Insurance against what?  I'm assuming the whole IIC bus is on the same
>board.  Connecting IIC pins is not different that connecting other digital
>logic pins together.  It's safer actually, since IIC is always open
>collector and the drivers therefore can't fight each other.  Even if they
>did, that would be a bug to fix, just like it would be if you had two bus
>drivers trying to drive the bus simultaneously.
>
>Also, Rs needs to be small compared to Rp, else the divider will cause the
>master not to see a slave driving the line low.
>
>
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