Digital compass

All information pertains to the N900.

= Connection options =


 * Optical (use one of the cameras, plus image processing)
 * Best to use user-facing camera, so the world-facing can be used for capturing the world image for AR
 * USB
 * Unknown if USB host possible.
 * Unknown if power is available from USB.
 * IRDA
 * Seems unsupported at this point
 * Bluetooth
 * Bluetooth data
 * Bluetooth audio - sending analog signals via Bluetooth microphone for digital signal processing on the N900
 * FM radio
 * Requires headphones be connected
 * Signal processing of audio in software

= Compass chips or sensors =
 * Honeywell HMC5843
 * I2C interface
 * Magnetometer requires vector math on client side for interpretation, see OpenMoko i2c compass project for more info
 * Dinsmore analog

= Ready-built compass modules =
 * Ocean Server OS4000
 * Ocean Server OS5000
 * USB and RS232 interface

= Microcontrollers =

= Converters =
 * I2C to RS232
 * http://www.gedanken.demon.co.uk/rs232-converters/i2c.html
 * http://www.i2cchip.com/
 * RS232 to Bluetooth
 * Sparkfun BlueSmiRF Gold
 * I2C to USB
 * http://www.harbaum.org/till/i2c_tiny_usb/
 * I2C to Bluetooth
 * http://www.emv-electronics.com/de/intro/i2cbusadapter.htm (seems unavailable for purchase)

= Designs =

Optical image processing of compass

 * Periscope-like mirror