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angle determination using ADXL345

Posted: Sat Aug 18, 2012 8:35 am
by ayush

i am working on a project were i need to find the angle or tilt using the ADXL345 sensor.but i am facing problems in the calculation of it like how to calculate the angle when i am using different g's value. moreover, it's datasheet said that the output can be set to 10bit or 13bit but still i am getting 16 bit output.can u suggest some tips?

Re: angle determination using ADXL345

Posted: Sat Aug 18, 2012 10:23 am
by abhimanyu
You will have to use the Cosine functions to get the output in Angles. (Direction Cosines)
You may read more about it here: Starlino - IMU Guide
(Just before Part 2. Gyroscope starts)

The datasheet of ADXL345 mentions changes in Output Resolution with Changes in g-force. Look at Page 4 -> Under Specifications -> Row 2 -> Output Resolution may go up to 13-bits at high g-forces (16 g's).

Also, on Page 27, FULL-RES bit is mentioned. Here is an excerpt:
When this bit is set to a value of 1, the device is in full resolution mode, where the output resolution increases with the g range set by the range bits to maintain a 4 mg/LSB scale factor. When the FULL_RES bit is set to 0, the device is in 10-bit mode, and the range bits determine the maximum g range and scale factor.