is it possible to detect a tap without using of DMP feature of MPU9250?

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

Coppers Copernicus — Tue, 26 Mar 2019 10:25:45 GMT

Hey Ashish, any valuable info regarding double tap? I want a similar thing to integrate into my project. Please shed some light if you have found the way. Thanks in advance.

Regards,

Nikhilesh

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

Sigurd — Thu, 09 Nov 2017 15:30:59 GMT

Maybe look into what separates the tap and a little shake?

With a tap, you are maybe above the threshold for a small amount of time, but with a little shake, you are above the threshold for a much longer time? So you could maybe use a timer to measure the time you are above the threshold, and if you are above the threshold for a certain amount of time, you know that this is a little shake and not a tap?

Maybe InvenSense also have some ideas on this also.

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

ASHISH — Thu, 09 Nov 2017 14:30:44 GMT

Thanks sigurd,I have posted same question on( invensense)support centre as you have mentioned in your comment hope will get reply soon.I am measuring the tap on z axis so without tap I am getting X=32767,Y=32767,Z=48768 constant readings...When I tap the board on z axis I got this values 1Tap-X=13403,Y=39351,Z=65534,2Tap-X=-1,Y=30119,Z=65534,so I set threshold value for z axis only coz if I tap on Z axis then respective Z values changes as I mentioned above like Z=65534 .should I need to set threshold for other two axis also for accurate tap detection.i have made algorithm like this 1.I set threshold value for z axis only and that is 55000 . 2.I set a counter for the z axis values when I tap the board and my axis values crosses 55000 thresh more than 4 times then executes motion function(); 3.I have also set counter for this when my motionfunction():; get called two times then I am glowing a led for indicating that tap is detected and printing "tap detected" on screen. But my actual problem is when I place the board on horizontal table and I tap the board led glows.and when I take the board on my hand just move (shake) little but then also the led glows.how should I make difference between the tap and little shake?

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

ASHISH — Thu, 09 Nov 2017 14:05:15 GMT

Thanks mango I have posted same question on invense.

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

Sigurd — Thu, 09 Nov 2017 13:39:57 GMT

Ok, then you could maybe see how these values change when you tap on it. Then you can maybe have some threshold, so when the values go pass this threshold, you know that you have a tap.

As MANGO mentioned, you could also ask InvenSense, and see if they have any tips on the best way to implement this. They have a Discussion Forum you could maybe post this on, and also a “Support Center & FAQ”.

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

MANGO — Wed, 08 Nov 2017 23:39:05 GMT

Hi, I think you should ask this at InvenSense, the manufacturer of MPU series.

As far as I know, you can configure the MPU to toggle a GPIO interrupt for free fall, data ready, etc events.

In short, this question is not related to nRF series.

Check the interrupt events of the MPU or contact the InvenSense team.

Since you have a successful interface between the nRF51 and the MPU, the event configuration will be easy for you.

-Best Regards

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

ASHISH — Wed, 08 Nov 2017 17:00:50 GMT

Hi,sigurd Yes,I have gone through that git repo you have mentioned in your comment and I have successfully interface mpu with nrf51822. I want to detect a tap(means I set my mpu on a board) if I tap the board my tap must get detected ( print the message on the screen single tap detected).I want to do this without using of DMP feature of mpu.i want to do that using just raw values of mpu.ho do I do this? When my bord is on horizontal position with +-2g setting and using low power mode I got this mpu readings X=32767,Y=32767,Z=48767 how can I detect a tap with the help of this reading?

RE: is it possible to detect a tap without using of DMP feature of MPU9250?

Sigurd — Wed, 08 Nov 2017 16:10:25 GMT

Hi,

What do you mean by tap ? You want to detect if someone tap their finger or something on the board?

Have you seen this git repo with MPU examples? github.com/.../nrf5-mpu-examples