open-headtracker versions (http://www.rcgroups.com/forums/showthread.php?t=1677559&page=207)

all founded forks of original DIY_Headtracker ( in DIY_Headtracker_firmware_orig )

DIY_headtracker-8mhz - port to 8mhz Arduino (as is) and others for different sensors (as is)

main one: DIY_Headtracker_firmware_fastserial - changed to FastSerial library with printf_P, uses ATAN2 (no more NAN!), add noise filter and some cleanup

• sensor timer moved from timer0 to timer2 - so we can use millis()!
• odd slow Wire library changed to fast I2C library
• I2C library altered to speed up and reduce size
• added full compass calibration with hard-iron and soft-iron corrections
• addede Four Order filter to accel data
• all code refactored to fit all the above
• calculations optimized so now measure & calculations uses only 4ms
• gyro filter changed from 98Hz to 20Hz

• It works!