This is a breakout board for Honeywell's HMC5883L, a 3-axis digital compass. Communication with the HMC5883L is simple and all done through an I2C interface. There is no on-board regulator, so a regulated voltage of 2.16-3.6VDC should be supplied. Project description, more information and ordering can be found at https://www.sparkfun.com/products/10530 Datasheet: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Magneto/HMC5883L-FDS.pdf Example code: http://sfecdn.s3.amazonaws.com/datasheets/Sensors/Magneto/HMC5883.pde Bildr Tutorial: http://bildr.org/2012/02/hmc5883l_arduino/ Digital Compass How-To Video: http://www.youtube.com/watch?v=sBKHdt0OdPg