Accelerometer(LIS303DLH) Register settings for ''linear acceleration+AHRS''

[harinath]

Posted on July 13, 2011 at 06:40

I have iNEMO V2 Board.  I want to use the inbuilt( embedded) filters of the geomagnetic module.How can i change the register settings of the Accelerometer ( LIS303DLH). I know there are two ways to do this ( iNEMO Suit GUI ,  Using the API)

1. In iNEMO Suit GUI  if the AHRS Mode enabled ,Accelerometer parameter settings ( High-Pass Filter,ODR, reference), they are grayed out. Why is this ?

2. My investigation reveals iNEMO V2 board can't give ''linear acceleration(without gravity or tilt)'', when the AHRS enabled. Is this true ?

3. Now, I desperately need linear acceleration along with AHRS. If above 2 points are true. I really need help of ST to upgrade the firmware to provide linear acceleration, acceleration( linear acceleration+ gravity), along with AHRS.

4. If i want to change accelerometer High-Pass Filter settings, and also want AHRS output, what should i do ?

I completely depended on iNEMO V2, spent my fund for my research, I can't proceed further if i don't get linear acceleration. Please help ST !!! 

Thanks.

[Fabio]

Posted on July 13, 2011 at 15:11

Hi Harinath,

1.

      

These are grayed because of AHRS admit only fixed parameter for Filters, ODR and so on.

2.,

3. &

4. You have to modify the firmware to do this. However, AHRS algorithm is based on Gravity. It uses this reference to know the tilt of the board, if you act on High Pass filter to remove the gravity you miss this reference.

Since, to help you I have a further question: how do you elaborate the data? You can integrate iNEMO within a larger context such as Matlab or Visual Studio Project. Where you can process the accelerometer data by implementing a high pass filter.

Best Regards

iNEMOâ„¢ Team

 

[harinath]

Posted on July 14, 2011 at 08:35

Hi Fabio,

I'm using Visual Studio 2008( sometimes MATLAB for testing).I need AHRS data along with ''linear acceleration''.

1. Would you explain a way how to implement a High-pass Filter(HPF) which has the same response as embedded HPF ?

2. Does this HPF completely removes tilt( gravity) to produce linear acceleration ?

3. In LIS303DLH datasheet talks about ''linear acceleration''. Does this mean, it gives only ''linear acceleration(gravity removed)'' ?

4. Would you give any mathematical steps how to remove tilt from the acceleration to get linear acceleration.

Thanks.

[Fabio]

Posted on July 25, 2011 at 16:24

Hi Harinat,

Below some comments:

1.

      

For sure an emulated on PC HPF has not the same performance of an embedded one, we suggest to refer to Matlab or “numerical recipies� book to get info.

2.

      

If it is well implemented, yes.

3.

      

No.

4.

      

There are many papers and books that explain this. I suggest to look for “inertial sensing of human movement�, it is a thesis with ISBN 9036518237

Best Regards

iNEMOâ„¢ Team

Hi Fabio,

I'm using Visual Studio 2008( sometimes MATLAB for testing).I need AHRS data along with ''linear acceleration''.

1. Would you explain a way how to implement a High-pass Filter(HPF) which has the same response as embedded HPF ?

2. Does this HPF completely removes tilt( gravity) to produce linear acceleration ?

3. In LIS303DLH datasheet talks about ''linear acceleration''. Does this mean, it gives only ''linear acceleration(gravity removed)'' ?

4. Would you give any mathematical steps how to remove tilt from the acceleration to get linear acceleration.

Thanks.