we are using the self-test on the LSM6DS3USTR and it has started to fail and is shutting down our production. Is there a known problem that would create this situation? If there is no answer, we may need to shut down the self test to resume production.

DGree.6 · ‎2020-09-17

This is quite urgent!

Eleon BORLINI · ‎2020-09-24

Hi Dale,

Thank you for your appreciated feedback.

Yes, please consider that the important timings for the self test are described in the lsm6ds3_self_test.c (and in the AN4889 app note) and are the following ones:

#define    BOOT_TIME   20 //ms
#define    WAIT_TIME_A     200 //ms
#define    WAIT_TIME_G_01  800 //ms
#define    WAIT_TIME_G_02   60 //ms

>> I also heard a rumor that something changed in the firmware in the LSM6DS3. Is that true?

Well, I can't know if you changed something in your firmware... ;) But I suggest to check the last fix on Github, if it is aligned with your fw.

-Eleon

DGree.6 · ‎2020-09-24

I certainly do not understand your leap from firmware inside the LSM6DS2 to our firmware. We have absolutely no control of the firmware inside your IMU chip. Could you please clarify this so that this makes some sense? We are still trying to figure out why this problem suddenly appeared after months and many tens of thousands of successful tests.

Eleon BORLINI · ‎2020-09-24

We may refer to different things, I suppose. I believe you built up your custom application, composed by an application processor + a LSM6DS3USTR. I'm referring to the firmware / software that is running on your application processor, and in particular to the part dedicated to check Self test check in production. No changes inside the electronics of the sensor, from ST side.

Please let me know if I misunderstood your point.

-Eleon

DGree.6 · ‎2020-09-24

That’s our point of confusion. Our application firmware has not changed from the very beginning of this product and then suddenly there were 20-30% failures that presented accelerometer and/or gyro data. We did all kinds of experiments to find out that the problem tracked the LSM6DS3 chip and only in the self-test. The older chips worked, the newer chips did not. This started in the middle of a reel and as I said before, reel changes did not solve the problem. And we also convinced ourselves that the software was not the problem through several experiments.
I will track down our firmware timing to be sure they are following the rules.

Eleon BORLINI · ‎2020-09-24

understood... could you please ask your team if they can send you (and then to me) two pictures of the top package marking of the LSM6DS3s, one of a good sample and the other one of a failed sample? There are some tracking information on it.

Thanks

-Eleon

Eleon BORLINI · ‎2020-09-28

Hi @DGree.6 ,

Please let me know if you eventually managed your issue, or in case if we can give further suggestions to you.

-Eleon

DGree.6 · ‎2020-09-28

The firmware changes have corrected this problem. Last week, the “failed�? no-read units all passed, with only a couple of exceptions. There are only a few loose ends to follow up on.
Thanks for the support.
Dale