Ashtead's Journal: More hardware fun with the Western Digital Worldbooks

I've had these Western Digital Worlbook units for a while now, and although I soon got the shell access to the Linux system on them, I didn't investigate them further until last week.

What I found is that there is an SMBUS/I2C function available on them, and that the kernel, right out of the box, contains the necessary drivers for this. The actual connection is to where an omitted RTC chip would have been. (The specific details is that U9 pin 5 is SDA, U9 pin 6 is SCL, U9 pin 4 is GND, and then get 3.3V from the serial-port connection, J4 pin 1) I hooked up a DS1621 temperature sensor chip there, and managed to talk to it via the /dev/i2c-0 device and the i2c-dev module.

I'll be making a nice hardware modification (no loose wires all over the place) and there is space for an additional circuit board inside the cae. Only issue now is what kind of connector to use for the external i2c connection, for which I need four wires: Serial Clock, Serial Data, Ground, and Power for the pull-up resistors.

This opens up many interesting possibilities, imagine some kind of self-contained data-logging arrangement, where the system pulls information from sensors on the I2C-bus and stores it on the disk. Then just have this sit on the network somewhere...

Of course the USB-connector can be used for something similar, perhape even higher-bandwidth -- but the sensor hardware would not be that simple!