I2C I/O Expander PCF8574 hanging?

[NavMicroSystems]

That's interesting. Kinda TRIS refresh. Well it make sense, if we RTFM they say clearly

Originally Posted by TFM
...The I/Os should be high before being used as inputs

Something to remeber for all here!

Thanks Dave.

Steve,
you are right,
that's what the datasheet says,
but it is not really clear.

When initialising the PCFs I do first write $FF to it.
From that point on there are only READs.

So the the I/Os have been set HIGH before being used as inputs.
(The System has been running for about six months without any error, last week was the first time I found a gap in the log.)

The DataSheet doesn't tell that you have to set the I/Os HIGH before every single READ.

However,
if that solves the problem I can live with it.
(I have already changed my READPCF-Routine)

Thanks again to Dave for pointing that out.

EDIT
OK, that takes some extra clock cycles, so I had to recalculate the timing.

I'll put the new FIrmware Live on Monday and let you know wether or not the problem occurs again.