LIS3DHTR data length

Rob1 · ‎2016-11-01

Posted on November 02, 2016 at 07:41

What is the actual data (x,y,z) length. When I'm reading the acceleration data , the lowest 4 bits

are 0. This would indicate the data is actually 12bit , left justified. The datasheet however

say's the FIFO is 10bit.

Does this mean that the actual usable data is 10bit?

Cheers

Neddie

Miroslav BATEK · ‎2016-11-02

Posted on November 02, 2016 at 16:57

Yes, the output data are 12bits, left justified.

However internally in the FIFO only 10 most significant bits are stored.

When reading FIFO, you will read 16bits raw data, divided by 16 you will get value in [mg].

Two least significant bits will be always 0.

Best regards.

Miroslav

dave239955_stm1_stmicro · ‎2016-12-02

Posted on December 02, 2016 at 12:10

I am only getting 10 bits from my LIS3DH. I'm using it in its most basic setup (+/-2g and 1sec update) and if I read the OUT_X_H and OUT_X_L, etc, registers directly (no FIFO) it reads from 4000h to 0000 for +1g to 0g (as I'd expect). But it's counting by 40h steps - the lower 6 bits are always 0. This is equivalent to 10mg steps and I need better.

I note there is a 'high res' bit in control register 4, but when I set this, I get completely differnt readings form all axiis and they still count by 40h. The function of this bit is not described in any of the ST datasheets or app notes.

Can anyone help?

Dave