Using Sensorfusion algorithm for getting exact reading from Acc+Mag+Gyro ?

[Amit_Kumar1]

Hi

I am using FXOS8700CQ ACC+ mag and FXAS21002 Gyro based FRDM-AGM01 Board, Is there any appnote to interface ACC+Gyro to get exact angle, after this I would be trying to interface magnetometer with these 2 sensors for getting the roll pitch and yaw. I used the sensor fusion toolbox and its library, the data was very precised I wanted to understand and write my own code for interfacing all these 3 sensors. but the raw values had lots of offset wanted to get rid of these offset. is there any appnote for this ? Thanks in advance.

Regards

Amit

[michaelestanley]

Amit,

All documentation is included in the kit doc directory.  The kit includes several different fusion algorithms.  One of those is acc+gyro.  You can then read orientation directly from the output structures of routine and (if that is what you are trying to do) manually fuse it with the mag.  I would expect performance to be a bit better than a pure eCompass (mag+accel), but not as good as the full 9-axis fusion routine (which you also have).

Good luck,

Mike

[Amit_Kumar1]

Hi Michael

I tried extracting the raw values using both the (sensor fusion library + toolbox recording) and (My basic interfacing code + terminal s/w) keeping the FRDM board stable at same place at same orientation, but the values I got is different. I am sorry for troubling you my only concern is I wanted to understand how things are working. Attached is my code with the o/p files. I have changed the I2C port of AGM board using the jumper position. Please help me in resolving this issue.

Warm Regards

Amit

[michaelestanley]

Amit,

If I understand you, you are trying to compare raw sensor readings from our library versus those from virgin code you have written?  I can only recommend studying the drivers included in the fusion library.  They are well documented in the code, and are quite stable at this point.

Mike

[Amit_Kumar1]

Hi Michael

Thanks a lot for your time and patience. I went through your detailed documents. It Reflects the amount of research you would have been doing to get it work. Hats off for your wonderful work. Thanks a lot for providing such an effective library. I had few questions

1) How do I select which sensors to be used ? In My FRDM-STBC-AGM01 board I have FXOS8700CQ and FXAS21002 I don't have any other sensors and was thinking if there is an option to select only these sensors.

2) Is there any option to change the sensitivity i.e for acc 2g/4g/16g or gyro 2000dps/250 dps ?

Regards

Amit

[michaelestanley]

Choice of sensors usually is a mix of technical and business considerations.  The table below shows strengths and weaknesses of the various types of sensors. The board you have has accel+mag+gyro.  The choice of which accel or mag or gyro will depend on desired sampling rate, full scale range, interface type, package size, cost and so forth.

The FXOS8700CQ supports several g ranges (2/4/8).  You can change this in the drivers.c file.  The other two sensors on your board have only a single full scale range.