Well, I got my code working properly now.  Your NACK routine helped me figure 
it out.  Thanks again.  I wrote page-write code for specific Mchip and Atmel 
Serial EEPROM's which both work properly with 4.7k pullups (@ ~100khz), 
though I expect in an actual project, I'll use some smaller values.

Absolutely agree about the logic analyzer -- I would've given yet another arm 
and leg for one while debugging, but I ended up using a very very primitive 
logic analyzer -- I changed the oscillator to external RC osc and slowed it 
down to about 20 hz (yep -- Hz, not khz).  Add a couple buffered LED's to the 
SDA and SCL lines, a pencil and paper in hand, and I got a true logic 
analyzer plot! :-)

BTW, I found out that MPLAB SIM has a logic analyzer plot, but it's not very 
effective when trying to measure what's happening on a line that gets 
pulled-up/down by various external components, and temporarily changing the 
code to high or low outputs can only indicate so much without changing the 
timing.

Rather than getting a large desktop analyzer off ebay or so, I came up with an 
idea to build a simple logic analyzer, but haven't had the time to implement 
it yet -- that'll be another discussion later.  Need to spend some time 
implementing the Serial EE code into an application first.

Cheers,
-Neil.



On Monday 26 September 2005 09:28 am, michael brown scribbled:
> ...
> ...
> ...
> That's why I mentioned using the stiff pull-ups.  Do everything you can
> to be sure that when it doesn't work that it's a logic problem and not
> an actual electrical one (slow rise times or whatever).  I wish I had a
> logic analyzer or even a DSO would be really nice.  I got mine working
> with a couple of serial EEPROMs and a Dallas RTC on the same bus built
> up on a solderless breadboard.  I had some trouble with rise times, but
> I'd already experienced odd behavior of a shift register when the rise
> time was too slow.  It wasn't like I immediately recognized the symptoms
> (cause they were different), but previous experience had left me with
> one more thing to try.


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