>  I am trying to get one PIC to talk to another via Bit Bang I2C routines
>  from the "Serial PIC'n" book.   I cannot get an acknowledgement from
>  the slave unit when it is addressed.  Actually I have four slaves, and
>  none of them give an 'ack' response.  All four have different
>  addresses. I have pullups on the clock and data lines.

I am not familiar with these routines, but a couple of suggestions.

1. What happens when you have only one slave attached.

2. have you tried to access another device such as an eeprom, without any of
the slaves attached? This would verify your master code is OK before you try
and fault find a possible problem in the slave code.

3. Are the slave addresses set correctly (i.e. the high 7 bits, not the low
7 bits.

You probably need to try (2) before (1). Also get a copy of the I2C
specification from the Philips web site at
http://www.philipslogic.com/products/collateral/i2c/ and look for the
specification link about 6 to 8 items down if you have not already got it.
This is the bible when it comes to I2C.

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