I'm building a clock using Numitron tubes for the display.

The display hardware works fine - using PBP 3 and a 16F886

I don't however, seem to be able to read any of the registers of the DS1307-based RTC clock module I'm using. I'm using the bit-bang I2CREAD and I2CWRITE commands, I don't have a scope, but my logic probe shows pulses on both SDA and SCL

My thought was, "since the master clocks the communications, using the internal oscillator should be fine. It shouldn't matter is its off by a couple percent".

Was I wrong? Should I be using a crystal?

I'm just trying to get it running, and this thought occurred to me.

Thanks for any help