Dear all,

I've just subscribed to this discussion so please feel free to correct my
 etiquette.

I have a problem using the PIC16C65 as an I2C slave returning data back to the
 master.
Things work fine until the end of the first data byte returned.
The SCL and SDA line stay low. I believe this is the PIC's fault and not the
 master, because the master
continues working when the PIC is reset.

I've checked everything I can: the CKP bit is cleared at the right time, the
 TRISC registers indicate the I2C
output pins should be hi-z, there are no error conditions, etc. I thought the
 problem was sending the wrong
number of data bytes, and tried to write interrupt code to examine the ACK bit
 and thus eliminate this possible
culprit. The data sheet explains no way to do this. I've tried loading dummy
 null bytes into SSPBUF before
setting CKP. I've tried trying to force SCL and SDA to hi-z by software.

I've trawled the web and come back with low quality info and amateur HTML.
 Eventually I found the Microchip BBS
site and sifted out SSP I2C SLAVE related messages. Some have noticed the ACK
 bit is unreadable from
interrupts. Some complain of lock-ups similar to mine. Quite a few express
 annoyed with the fact that the SSP
only does slave duty not master (like finding a UART which provides a TxD pin
 you have to bit-bang!). Microchip
don't seem to answer queries which highlight the shortcomings of their chips -
 perhaps a wise move in
litigatious America.

I've also asked all my trade contacts without success. Ominously, one said his
 experienced predecessor had
tried and failed to get I2C fully working with PICs and eventually implemented
 some proprietary 4-bit bus! So I
don't think my problem is trivial.

Has anyone had these problems and if so how were they solved?

Thanks for your time in reading this.