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kriswiner / MPU9250

Arduino sketches for MPU9250 9DoF with AHRS sensor fusion
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Magnetometer signal looking strange #195

Open iamchrisb opened 7 years ago

iamchrisb commented 7 years ago

Hey Kris... I am just wondering if this signal from the magnetometer looks strange to you. I expected way more smooth lines.. is this due to the low frequency of the magnetometer or did I something wrong? I used one of your sketches as a basis

image

kriswiner commented 7 years ago

Not sure I understand this. At 100 Hz, the lines should be constant for 10 ms; instead they seem to vary every 0.15 ms or ~6000 Hz. How is this possible?

On Tue, Oct 24, 2017 at 1:17 PM, Christopher B notifications@github.com wrote:

Hey Kris... I am just wondering if this signal from the magnetometer looks strange to you. I expected way more smooth lines.. is this due to the low frequency of the magnetometer or did I something wrong? I used one of your sketches as a basis

[image: image] https://user-images.githubusercontent.com/1254349/31965809-c92d74ee-b908-11e7-91ee-cbe3aaf9ce82.png

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iamchrisb commented 7 years ago

so basically this is wrong? the accelerometer and gyro look fine to me (I can upload an image later). Maybe I am asking too much, but could you post an image of your magnetometer output? I couldn't find useful ones and I can ask no-one besides you.

kriswiner commented 7 years ago

Should be new data every 10 ms if using 100 Hz for the mag.

On Tue, Oct 24, 2017 at 4:58 PM, Christopher B notifications@github.com wrote:

so basically this is wrong? the accelerometer and gyro look fine to me. Maybe I am asking too much, but could you post an image of your magnetometer output?

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iamchrisb commented 7 years ago

not sure, if I am using 100 Hz for the mag. I just used one of your sketches and tweaked the I2C for the arduino to 400kHz. Maybe I can find out whats "wrong". Thanks for your reply!

Just one question, when I read the datasheet of the mpu9250, I can only find informations like "the mag is operating at 8Hz", why should it be 100Hz? wouldn't 8Hz mean that I have an update every 60/8 seconds or every 7.5 seconds?

kriswiner commented 7 years ago

The AK8963C can only run at either 8 Hz or 100 Hz, so you should expect to see new mag data every 125 ms at 8 Hz or 10 ms at 100 Hz, not 0.25 ms. Maybe something wrong with the way you are reading from the mag? You can poll the status ready bit and only read the mag data when this is 1.

On Wed, Oct 25, 2017 at 2:29 AM, Christopher B notifications@github.com wrote:

not sure, if I am using 100 Hz for the mag. I just used one of your sketches and tweaked the I2C for the arduino to 400kHz. Maybe I can find out whats "wrong". Thanks for your reply!

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iamchrisb commented 7 years ago

I will try to find it out, thanks for your fast replies as always!