Hi Erik,

some corrections:

1) there is never need to disable interrupts, since no maximum timing requirements on the I2C bus.

2) full speed (100kBaud) can only be selected on a crystal up to 8MHz which was equal the 552 at 16MHz.
On any crystal above 8MHz up to 20MHz only very slow baud rates can be selected.


3) a software routine need less code, because you must resolve every state on using the I2C hardware.
E.g. also if only the single master mode was used, a noisy spike on the I2C bus may enter some of the slave modes. If you not handle it, your I2C hardware was blocked forever.


So the only decision, which must be made:

If only single master mode was used, a software I2C should be preferred.
On all other modes (multi master or slave) the hardware I2C must be used.


Peter