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Thanks for the feedback ! Glad your issue is solved ... View more

Hi boardarch, That's a very nice target ! Unfortunately I do not know of any consumer grade accelerometer which can achieve this kind of accuracy, especially over a wide temperature range. The BNO055 has built-in calibration which can typically keep the pitch and roll error <2 degrees. This is an order of magnitude higher than your requirement. With good mechanical design and smart calibration routine (not automatic like the BNO055), <0.5 degrees can be achieved at room temperature, but would require periodic manual recalibration. https://community.bosch-sensortec.com/t5/Knowledge-base/BMA4xy-accelerometer-series-design-guide/ta-p/5837 o_o ... View more

I would recommend BMI085 or BMI088 depending if it will operate in a vibration prone environment ... View more

In your case, you mention that you don't need absolute heading, and therefore : you don't need the magnetometer at all. Please use the IMU working mode. That solves the magnetometer calibration issue. Gyroscope calibration only requires the device to be static, and takes less than a second, I would recommend to leave the BNO055 do it's thing. Accelerometer calibration is what causes pitch&roll offset and this would be the only parameter that you may want to save and reload. Most applications do not need to wait for accelerometer calibration, what is your target accuracy? ... View more

It would greatly help if you could confirm the SPI transactions with a logic analyzer or oscilloscope, to make sure they match the communication protocol. ... View more