Configuration of the Click recognition on the LSM9DS0

Nicolas Hugget · ‎2017-05-23

Posted on May 23, 2017 at 17:04

Hi,

I am working with the Lsm9ds0 sensor and i would like to properly configure the Click recognition.

After reading the datasheet I manage to rise an interrupt on a click but i still have a question about this functionality:

What is the unit of the threshold on the CLICK_THS register, is it 16 mg per LSB as in the Act_THS register or is depending of the range of the accelerometer ?

Secondly I would like to configure a High-Pass filter in order to reduce the noises on my click detection. It seems to be possible using the CTRL_REG0_XM, REFERENCE_X and REFERENCE_Y registers.

Could someone confirm me that the � Reference value � mentioned on those register�s description is the cut-off frequency of the filter.

Regards,

#noise #click-recognition #embedded #lsm9ds0

Miroslav BATEK · ‎2017-05-30

Posted on May 30, 2017 at 18:23

Ths6 through Ths0 define the threshold which is used by the system to start the click detection procedure. The threshold value is expressed over 6 bits as an unsigned number.

1 LSB of the threshold = full scale/128.

The Reference registers do not define the cut-off frequency of the high-pass filter. The reference value is subtracted from the output value in case 'Reference signal for filtering' mode is used.

Nicolas Hugget · ‎2017-05-31

Posted on May 31, 2017 at 11:45

Thanks a lot for this answer ! It is exactly what i need.

Raul Quesada Navarro · ‎2017-10-30

Posted on October 30, 2017 at 13:58

Hello,

I'm also interested in settung up the click functionality of the LSM9DS0, but I don't completely understand what you mean.

Could you please express it with an example of a good value for the configuration register?

Thanks!

Miroslav BATEK · ‎2017-11-02

Posted on November 02, 2017 at 10:23

As start you can use following configuration for single click recognition:

The accelerometer should be configured to ODR = 25Hz and FS = 2g.

To link the output from click detection to INT1_XM pin set CTRL_REG3_XM (22h) to 0x40.

Raul Quesada Navarro · ‎2017-11-16

Posted on November 16, 2017 at 17:12

Hello again, finally I could make the click function work, but still there are a couple of open questions:

Could you please define a little better what is the meaning of TIME_LIMIT, TIME_LATENCY and TIME_WINDOW registers?

I've been playing with some values around, but still I couldn't figure out what's their exact behavior. In the datasheet the useage is quite vague...

Thanks!

Miroslav BATEK · ‎2017-11-17

Posted on November 17, 2017 at 15:02

If the device is configured for single-click event detection, an interrupt is generated when the input acceleration on the selected channel exceeds the programmed threshold, and returns below it within a time window defined by the TIME_LIMIT register.

If the device is configured for double-click event detection

, after the first click has been recognized, the second-click detection procedure is delayed for an interval defined by the TIME_LATENCY register. This means that after the first click has been recognized, the second click detection procedure starts only if the input acceleration exceeds the threshold after the latency window but before the window defined by TIME_WINDOW register has expired.

You can check chapter 8 in application note

http://www.st.com/content/ccc/resource/technical/document/application_note/77/ed/e7/e1/28/5a/45/d6/CD00290365.pdf/files/CD00290365.pdf/jcr:content/translations/en.CD00290365.pdf

which describes the click detection features. Even it is for LIS3DH the principal functionality it the same.