LIS3DSH: incorrect update frequency

[kazu hara]

Posted on November 27, 2017 at 09:10

Hello All,

I configured ODR to 1600Hz at CTRL4 register on LIS3DSH.

It works perfectly except for update frequency.

INT1 pulse outputs with 600us interval! I attached Oscilloscpe at INT1 pin.

It should be 625us(1s/1600 = 625us).

Could anyone kindly help me what is wrong with my setting, hardware...?

[Miroslav BATEK]

Posted on November 27, 2017 at 14:19

I don't think it is an issue. The ODR value in datasheet is typical value and can be slightly different in each sensor.

[kazu hara]

Posted on November 27, 2017 at 15:12

Ok, I understand it is spec.

So if I want to get INT1 interrupt with exactly 625us interval, what should I do?

[Miroslav BATEK]

Posted on November 27, 2017 at 17:51

Unfortunately it is not possible to fine tune or adjust the ODR, so it won't be possible to achieve exactly 625us.

[kazu hara]

Posted on November 28, 2017 at 04:05

Thank you very much for useful information, Miroslav.

I will use something like interpolation in order to get fine value.

[kazu hara]

Posted on November 28, 2017 at 06:03

I have one more question.

How much % is frequecy error of INT1 interval in worst case at LIS3DSH product?

For example, 1600Hz+-10% or something.

It is necessary for calculating buffer size for interpolation.

[Miroslav BATEK]

Posted on November 28, 2017 at 14:27

Unfortunately the ODR tolerance is not specified for consumer MEMS sensors.

I think +/- 10% should be enough, but ST doesn't guarantee it.

[kazu hara]

Posted on November 29, 2017 at 08:18

Thank you for useful practical information, Miroslav.

This is very good experience for me that I wll be cafeful for using consumer MEMS.