LSM6DSV gyroscope result issue

[Adam Hamilton]

Hi all

I am trying to debug an issue at work where we use the LSM6DSV accel/gyro IMU chip and I am running into a little problem

The result registers for the accelerometer and gyroscope both say that they return a 16-bit two's complement result, and I get the following

Gyro / Accel	Raw unsigned value (LOW | (HIGH << 8))	Two's complement value (Signed)	Result (mG or mDPS)
Accelerometer X	65524	-12	-0.732
Accelerometer Y	13347	13347	814.167
Accelerometer Z	111	111	6.771
Gyroscope X	32772	-32764	-143342.5
Gyroscope Y	32764	32764	143342.5
Gyroscope Z	37149	-28387	-124193.125

My system is sitting very still and on a somewhat level surface. The accelerometer seems correct. For a value close to 0, we see the unsigned value close to 0 or very high around 65535 which is what I would expect.

The gyroscope values for a zero rate I would expect to also be similar given the datasheet says this "The value is expressed as a 16-bit word in two’s complement"

My basic thinking is that these are expressed as a 15-bit word in two's complement.

I have double checked that the device is indeed an LSM6DSV chip as the WHOAMI register returned a value of 0x70

Just for additional reference, the gyro is configured in

high performance, 120Hz ODR and the sensitivity is set to 125 DPS

 

Any help would be much appreciated

[Adam Hamilton]

I found the issue for this. It seems that the first reading from the gyro is junk. This wasn't the case for the accelerometer however.