> >I wonder if i2c has no lower speed limit.  This would
> >allow anyone with a voltmeter to troubleshoot it.
>
> Well I am running it at 10KHz as I have opto-isolators in the
> circuit. Don't
> have any problems at that speed, and there are eeprom chips on the line as
> well as slave PICs.

        I once had a problem with a slave on my house monitor system which consists
of an I2C bus, about 30 feet in length. It wasn't always acking or returning
data properly. A PC is the master on the bus (connected to a parallel port
through a transistor buffer). So I built a program that let me toggle the
parallel port I/O lines by clicking buttons. I stepped through an I2C
transfer step by step by pressing these buttons. At the point of ack I
stopped, and went to the device to see what voltage was on the line. I had
the bus statically like this for about 5 minutes, after making the
measurements on both ends of the line I went back to the computer and
completed the transaction, the slave returned the correct value! :)So I2C
can definitely go down to DC. TTYL

PS. BTW for those curious the reason the ack wasn't received is that slave
was the last on the line and because of the pullup and line resistance by
the time the "low" reached my transistor buffer the voltage was too high to
turn off the transistor (around 0.7V). PSPICE confirmed that the 2N2222 I
used was not turning off enough to register the low. I put a diode in series
with the base and that solved the problem, a hack, but it worked.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads