jim@jpes.com wrote:
> No it isn't wrong.  Read the spec.

I have, and what you said is wrong and certainly bad advice.

The spec even shows a graph of the minimum allowed pullup resistor versus
supply voltage.  The document I use from Phillips (the originators of IIC)
is called "The IIC Bus and How to Use It".  I have had it so long I don't
remember exactly where on the Phillips site it came from, but I put a copy
temporarily at http://www.embedinc.com/temp/iic.pdf.

> For HS I2C comms, the min is 3ma
> pullup current, and the max is 12ma pullup current.

For *HS* mode, which is certainly not the default unless you explicitly say
so.  Using HS mode parameters with ordinary IIC devices (which the
discussion was about and your statement referred to) is actually out of spe=
c
and can cause the bus not to work.  Basically HS IIC is a different bus and
requires different devices and electrical parameters to IIC.  The general
signalling method and the name are the same, but the electrical specs are
incompatible.

HS mode came much later.  In fact, the addition of HS mode appears to be th=
e
main difference between the document I referenced above and yours.  In any
case, if you mean HS mode, you need to say so explicitly.  Most devices out
there are not HS mode compliant, and recommending up to 12mA without
explaining this applies to HS mode only is wrong and will get people into
trouble.


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