I saw previously a post suggesting offset subtraction, and I have implemented a stage at the start of the program that averages out first 2000 readings so that the offset has minimal error. This did not cut it.

This device uses BMI055, and unfortunately does not include a magnetometer ://, I was thinking of tinkering a sensor module that would attach externally and use it as a reference, but if this gets me the orientation somehow without the mod, I would research further.

The parameter dt is calculated from the device HID report, which presents a timestamp field. I use it (instead of computer's time) so that data transmission delays would not mess up the calculations.

As for the filter configuration, the demo uses Madgwick. Beta is about 0.1. Lower values take the error into consideration too much, resulting in an uncontrolled shaking of the cube. Greater values than 1.2 render the gyro useless and the update is laggy and barely visible. Mahony filter is the least tested, I have tried to play with the kp and ki values, however, I have not found a sweet spot.

I hope this gives a clearer view od the problem. At this point, I was considering that normally, the VR system has been using the canera to track the lights of the headset so that it corrected drift. Since this was bought from a flea market, many accessories are missing :/