Why don't I get any data from the TCM2 compass?
From MobileRobots Research and Academic Customer Support
Use ARIA's 'demo' program to test. Enter compass mode by pressing the 'm' key. The compass must be powered on using either the AUX1 or AUX2 power switch on the side control panel, and it must also be enabled in the firmware configuration -- connect with ARCOScf and set TCM2 to 1.
If you receive no data, even as you rotate the compass, use ARCOScf to connect to the firmware configuration and check that the compass is enabled, and set to use the correct serial port. Next, check that all connections between the compass and the microcontroller serial ports are not loose.
The robot manual contains some information about the TCM2 compass. Newer versions give a brief summary of the calibration process. The manufacturer's manual has more detail on this.
Use the ARIA class ArTCM2 to access its data.
The manufacturer's manual is at http://robots.mobilerobots.com/docs/all_docs/tcm2man.pdf . This manual includes instructions on how to calibrate it.