disable TWI hardware / broadcast ?

Currently there doesn't seem to be

Wire.end()

or similar available.

I'm having issues with I2C linking several boards. In mode a) (no I2C involved) the boards use PC4/PC5 to synchronize (works). In mode b) (I2C using Wire library) one board is master and the rest are slaves (works too). Going from a) to b) works, but going from b) to a) again doesn't.

I have the gut feeling that after having enabled I2C reading PC4/PC5 doesn't work anymore with

PINC = ...

Do I have to force I2C off with

TWCR = 0;

or is there an Arduino-ized way in the making?

Sending to a broadcast address would be an alternative as well, if it is possible.

...partially answering my own question:

putting

TWCR = 0;

after the I2C block in my code helps. The non-I2C block works again. Still I'd prefer something like "Wire.end()".