Two questions:

First, in the Bitbang I2C sample for the Uno is there a particular reason pins digital 2 & 3 were chosen as the data and clock? "Normally" it's analog pins 4 & 5. I noticed there is an issue with the Mega not allowing Analog pins to act as digital pins but that isn't an issue on the Uno's (that I noticed) .

Second, is this code for a particular I2C device? Why two calls to "i2c_tx_string" with arguments 0xCC and 0x33? I would have thought the second call would have been a call to i2c_rx_string instead (but there is no reason to set the buffer to a value).



Just askin

I am sorry I just noticed this on the UNO known issues page: http://www.robotc.net/wiki/ARDUINO_328_Known_Issues

Using Analog Ports as Digital I/O is not currently supported.

That explains why analog ports 4 & 5 are not used as data and clock for I2C. Sorry my bad.

In a future update, you'll be able to properly configure Analog sensors as digital. Right now ROBOTC goes behind the scenes and constantly polls all of the Analog sensors - we have to put a flag in to not scan a port as analog when it is configured as digital.

Thanks for the feedback!