3D Simulation Problems with MPU9250

RE: 3D Simulation Problems with MPU9250

Onur — Thu, 10 Jan 2019 08:29:14 GMT

Hi Einar,

Thank you for your answer and interest. I will consult invensense about this problem.

Have a nice day,

Onur

RE: 3D Simulation Problems with MPU9250

Einar Thorsrud — Tue, 08 Jan 2019 13:30:28 GMT

Hi Onur,

Regarding how it is used in the Thingy:52, I am not aware that there have been any specific HW measures for handling external effects. Both the hardware files and firmware source code for the Thingy:52 is available so that you can compare with your design. However, I suggest you contact Invensense regarding this, as MPU9250 is their product. They should have far more knowledge about it than us.

Einar

RE: 3D Simulation Problems with MPU9250

Onur — Mon, 07 Jan 2019 14:03:53 GMT

These are different problems. The first one is the problem that we encountered at Thingy52 and our own design in the first two photographs. We created our designs in these photographs by taking Thingy52 as a model.

https://www.dropbox.com/sh/prdz4jtk80pbm6f/AAANt1KdzRZN3Eqf1RKKk_Z5a?dl=0&preview=our_design_back.JPG

https://www.dropbox.com/sh/prdz4jtk80pbm6f/AAANt1KdzRZN3Eqf1RKKk_Z5a?dl=0&preview=our_design_front.JPG

We created an issue for the problem that we encountered in our designs in photos and Thingy52, but we could not reach the solution.

(https://devzone.nordicsemi.com/f/nordic-q-a/36351/3d-motion-problem-in-a-specified-movement)

For this reason, we have re-organized our project by taking other open source software instead of Thingy52 open source software. ( open source software that we used in reorganized project: https://github.com/kriswiner/MPU9250)

In reorganized project, we encountered a different problem than before. This is the second problem and we have never seen the second problem in Thingy52 tests. Second problem is about high sensor sensitivity against external effect like phones, tablet, even irons.

You can see this effect in videos:

https://www.dropbox.com/home/Nordic%20Issue

The reason we mentioned two problems was to specify all the stages we had progressed from beginning to end.The problem we are looking for solution at the moment is only the second one.

Thanks,

Onur

RE: 3D Simulation Problems with MPU9250

awneil — Mon, 07 Jan 2019 13:12:30 GMT

[quote userid="76078" url="~/f/nordic-q-a/42064/3d-simulation-problems-with-mpu9250/164252"]your design[/quote]

It's not my design.

https://devzone.nordicsemi.com/backstage/f/welcome-to-the-devzone/30115/how-to-know-the-respondent-is-nordic-employee-or-not

[quote userid="76078" url="~/f/nordic-q-a/42064/3d-simulation-problems-with-mpu9250/164252"]we've noticed the same problems at Thingy52[/quote][quote userid="76078" url="~/f/nordic-q-a/42064/3d-simulation-problems-with-mpu9250/164252"]this problem was not encountered when we use Thingy52[/quote]

I'm confused - was it seen on the Thingy, or wasn't it?

RE: 3D Simulation Problems with MPU9250

Onur — Mon, 07 Jan 2019 12:56:46 GMT

Yes, your design is open source and We have already made a design by taking sample from yours. Photos of our design are available at the link below.

Link: https://www.dropbox.com/sh/prdz4jtk80pbm6f/AAANt1KdzRZN3Eqf1RKKk_Z5a?dl=0&preview=our_design_back.JPG

https://www.dropbox.com/sh/prdz4jtk80pbm6f/AAANt1KdzRZN3Eqf1RKKk_Z5a?dl=0&preview=our_design_front.JPG

However, at the end of the detailed tests, we saw problems in 3D motion in this product. After that we've noticed the same problems at Thingy52. Therefore, we created the issue in the link below, but we could not conclude. (https://devzone.nordicsemi.com/f/nordic-q-a/36351/3d-motion-problem-in-a-specified-movement). So we decided to take sensor fusion algorithms from a open source algorithm, not from the Invensense’s closed libraries. (Sample open source project link: https://github.com/kriswiner/MPU9250) We have examined the especially calibration parts of the code we have shared above in detail and we have added multiple calibration steps to magnetometer, gyroscopeand accelometer. We must say that we have not seen any problems in our calibration codes. Because, after calibrating our product, it works exactly as we want unless there is an external effect. However, when an external effect added, our sensor is naturally affected and the 3D object that we see on the screen is slipping.

The last thing we want to ask you is: this problem was not encountered when we use Thingy52. Can you give us an idea to guide us to solve this problem? Or is it necessary to create an issue with Invensense? We want to take your idea.

Test videos with Thingy52 and our new design at the point affecting the magnetometer in the wall:

www.dropbox.com/.../AACvTHUUfCIZ8xxdyqOunDbCa

RE: 3D Simulation Problems with MPU9250

awneil — Fri, 04 Jan 2019 10:53:25 GMT

Again, the "soft iron effect" has nothing at all to do with the microcontroller you use - it is entirely down to the sensor and how you have deployed it in your design.

You will need to contact the sensor manufacturer for support in the application of their sensor.

[quote userid="76078" url="~/f/nordic-q-a/42064/3d-simulation-problems-with-mpu9250/163910"]Thingy52 has a speaker(so it has a magnet too)[/quote]

Are you sure?

Perhaps its a piezoelectric or MEMS speaker ...

[quote userid="76078" url="~/f/nordic-q-a/42064/3d-simulation-problems-with-mpu9250/163910"]Is the different hardware design [/quote]

The Thingy design is public - have you looked?

RE: 3D Simulation Problems with MPU9250

Onur — Fri, 04 Jan 2019 09:44:57 GMT

Hello,

Thank you for your reply.

Of course I understand.

The reason we chose Nordic MCU was the presence of a built-in bluetooth module. Therefore, it is a very advantageous MCU for us.

We were able to solve the initial position and the axis shift problem by calibration, so we have a system that works very well. However, we continue to have problems with soft iron effect. Electronic devices (mobile phones, tablets, etc.) that approach the device, and even the iron that comes near test board, affect the operating performance. It works very sensitive about this topic. On the other hand, we did not encounter this problem when working with Thingy52. We use the same DoF sensor as Thingy52. Although Thingy52 has a speaker(so it has a magnet too), it does not experience this problem. We have no idea how to solve this problem with calibration.

How did Thingy52 overcome this problem?

Is the different hardware design or did you work with InvenSense on this problem?

We couldn't get through this problem. Could you please help?

Thanks,

RE: 3D Simulation Problems with MPU9250

awneil — Wed, 02 Jan 2019 09:59:07 GMT

I can't see that this has anything to do with the Nordic MCU at all ?

There is something wrong in your code - you need to debug your code to find it, and fix it!

https://www.avrfreaks.net/comment/2418156#comment-2418156

It sounds like you have a calibration problem - ie, not properly calibrating your starting position.