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LSM6DSO(X) FSM Threshold Confusion

jspear
Associate II

Hi all,

This should be a question with a simple answer, but for some reason, I cannot find clarification. I am trying to use the Finite State Machine in the LSM6DSOX, and I have come across these examples below in this application note:

Screenshot 2024-03-15 095604.png

I'm confused on how to determine the THRESH1 values that are in the programs above. From what I read, the FSM uses the same linear acceleration sensitivity value as is output to the host MCU. As an example, my understanding is that I would take 3C66 (from program 2) as the number of LSBs, multiply that by the linear acceleration sensitivity value (i.e. 0.061 mg/LSB for FS = +-2g) and then that would be how you get the 1.100g that is in parenthesis. Doing the actual math with the different linear acceleration sensitivities for the different FS values, I don't find any of them equating the 1.100g.

I can't find any other information on how to convert the desired acceleration value in gs to the values provided to the FSM THRESH1 like is shown in the above image. Where might I be able to find this information?

Thank you for any help!

 

1 ACCEPTED SOLUTION

Accepted Solutions
Federica Bossi
ST Employee

Hi @jspear ,

As written in the AN5273 the FSM works in floating point on 16bit:

FedericaBossi_0-1710859178674.png

For the conversion you can use Unico GUI or MEMS Studio:

FedericaBossi_1-1710859204655.png

In alternative, you can also use this website: https://evanw.github.io/float-toy/ :

0x3C66 is 1.1:

FedericaBossi_2-1710859304810.png

 

 

In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question.

View solution in original post

1 REPLY 1
Federica Bossi
ST Employee

Hi @jspear ,

As written in the AN5273 the FSM works in floating point on 16bit:

FedericaBossi_0-1710859178674.png

For the conversion you can use Unico GUI or MEMS Studio:

FedericaBossi_1-1710859204655.png

In alternative, you can also use this website: https://evanw.github.io/float-toy/ :

0x3C66 is 1.1:

FedericaBossi_2-1710859304810.png

 

 

In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question.