Computing stuff tied to the physical world

Software- and hardware-I2C

In Software on Mar 15, 2010 at 00:01

Until now, the Ports library supported software I2C on the 4 “ports”, whereas hardware I2C required the Arduino’s Wire library. The unfortunate bit is that the API for these two libraries is slightly different (the Ports library uses a slightly more OO design).

See the difference in resulting code with and without Plug shield, for example.

Triggered by an idea on the forum, I decided to extend the Ports library, so that “port 0” gets redirected to Analog 4 (PC4) and Analog 5 (PC5), i.e. the hardware SDA/SCL pins on an ATmega.

So now you can use the Plug Shield with the same code based on the PortI2C class as with JeeNodes. Simply specify port zero when using this with an Arduino and a Plug Shield!

Here’s the Arduino example again, which no longer requires the Wire library:

Screen shot 2010-03-13 at 19.27.28.png

Note the use of port 0 to connect to hardware I2C pins.

The benefit is that all plugs for which code exists based on the Ports library (Pressure, UART, LCD, etc) can now be used on an Arduino with a Plug Shield.

A nice extra is that this will also work on an Arduino Mega, without requiring two extra patch cables to hook up to the hardware I2C pins.

Long live simplicity!