I2C Interface for the IXM

[Sam]

For those who haven't heard of it, I2C is a communication standard
used by a lot of peripheral hardware that one might want an IXM to
connect to.The IXM's processor has hardware support for 3 I2C
interfaces, of which 2 are accessible on exposed pins on the IXM.

Since the SFB library right now doesn't provide access to the I2C
interfaces, I decided to roll my own I2C interface library. This
library is still in development but for now it should support master-
mode transmission and reception (but not slave mode).

The I2C library is SFBHWI2C.cpp and SFBHWI2C.h. I've modeled these
after the SFB's serial interfaces. I'm also including a (very rough,
totally hacked) version of the Arduino's Wire library, for those who
are familiar with it. It doesn't expose all the functionality of the
I2C interface and I'll probably drop it later, but it will get you up
and running right away. The Wire library assumes you will use I2C1,
with SDA on West TX, and SDL on West RX.

The library is accessible from github here:http://github.com/downloads/
sambayless/Blimp/SFB_IXM_0.2.zip
You can also find it in our repo with a little bit of digging, but
that repository is for our project as a whole, not just the I2C
library. I'll try to release updates to the I2C library as bugs are
fixed.

I've tested the library writing to and reading from a MCP4725 DAC
(the type currently available from Sparkfun), at both 100 kHz and 400
kHz.

[Dave Ackley]

Wow, this is totally great!

As the code settles down we should think
about rolling this into the standard
distribution.

Now I have to go buy some MCP4725s and
try this out!

- Dave