LSM6DSV half precision error at ~180 degrees

Gorbit99 · ‎2024-01-16

Hi,

We're using the lsm6dsv's SFLP algorithm to calculate IMU rotation. Recently however we noticed that the resulting rotation has big gaps at around the 180degree mark. We believe this is because of the half float precision, specifically because there aren't a lot of representable values near 1. See below image for our calculated accuracy results which match the actual results we're seeing:

Federica Bossi · ‎2024-02-02

Hi @Gorbit99 ,

It is not an ST problem related to our libreries and sensors but it is an arithmetical problem when recalculating the weight. We are working to offer a workaround for the next generation IMUs.

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Gorbit99 · ‎2024-02-04

Hi Federica,

Sorry, but either we aren't talking about the same problem, or we are on entirely different pages about the issue.

The issue I am talking about is the following: With the number format the sensor is currently using, it is physically impossible for the sensor to send over a rotation representing 178 degrees. This isn't an arithmetical problem, it's simply a firmware problem, therefore it's an issue with the actual sensor, even if not with the hardware side of it.

And just so you understand my side of this issue, we've invested a not obvious amount of time and money into this sensor, so it'd be best if there was a workaround to this issue.

Federica Bossi · ‎2024-02-05

Hi @Gorbit99 ,

If you have bought a lot of parts and you need support, you should contact the OLS opening a ticket at this page.

This is not a case for st community.

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Gorbit99 · ‎2024-02-05

Dear Federica,

I have opened a ticket (two even), first I was told that this isn't a support issue and I should instead post here, then I was referred to this answer...

dorpomi · ‎2024-02-18

Hi @Federica Bossi ,

Can you please ask the engineers behind the IMU whether it is possible to flash another firmware on the IMU or override it on boot? We believe that the current issue can be resolved by simply encoding the rotational values in a slightly different format, and the ability to update the firmware is the first step towards a fix.

Simon24 · ‎2024-03-27

Hi all,

What is the status of this issue? Is there already a firmware update available? We bought a large quantity of lsm6dsv with the idea of using the sensor fusion function provided to us. We therefore need a solution to this issue really soon.