Get angular velocity from MPU-6050

[rflmota]

Hi,

 

Can anyone tell me how can i get DMP processed angular velocity from MPU-6050 using I²Cdevlib libraries for Arduino?!

 

Thanks in advance

[luisrodenas]

When you run the DMP example, add this line as shown here:

mpu.dmpGetQuaternion(&q, fifoBuffer);
mpu.dmpGetGyro(gyro, fifoBuffer);
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);

    dmpGetGyro will give you angular velocity. Anyway, I believe it is not processed, but the sensor raw reading multiplied by its gain.

[pico]

Hello,

 

I think the raw gyro data taken from the fifo (when DMP enabled) is scaled down. Because when i made a sensor fusion (verified), it doesnt match the DMP data. When i multiply the gyro data by 25 (experimantal), it works fine and matches the DMP data. Thus it is 2000*/s divided by 25.

 

And the accelerometer is also outputs ~8000 when idle. That means a 4g resolution.

 

Could anyone confirm the results?

[enginrd]

Hi Pico,

 

I have found the same results! And I have a theory about why.

 

For others: I found that dmpGetGyro gives rates of Roll Pitch Yaw (note the order) in counts that correspond to +-2000/25 = +-80deg/s (divide count by 32768/80)

 

My configuration: DMP FIFO set to 25Hz (see note below). getFullScaleGyroRange says 3 (2000deg/s), and I noticed it is set to this by dmpInitialize(). getFullScaleAccelRange says 0 (+-2g), but as others have pointed out, this does not seem to reflect the DMP output (dmpGetAccell), which is requires divide count by 32768/4=8192 implying +-4g. (getAcceleration() has a note suggesting 8192 is 2g sensitivity but I don't understand this.)

 

My first impression of the angular rates scaling is that it includes the fifo frequency I am using of 25Hz. Luisrodenas mentioned "multiplied by its gain" but I don't think this is what he meant. I have yet to explore this by changing the frequency, but I am now skeptical because you (Pico) are likely not using 25Hz. 

 

For anyone finding this wishing to change your FIFO rate, do a search in the MPU6050 header for inv_set_fifo_rate and read the note below it.

 

Hello,

 

I think the raw gyro data taken from the fifo (when DMP enabled) is scaled down. Because when i made a sensor fusion (verified), it doesnt match the DMP data. When i multiply the gyro data by 25 (experimantal), it works fine and matches the DMP data. Thus it is 2000*/s divided by 25.

 

And the accelerometer is also outputs ~8000 when idle. That means a 4g resolution.

 

Could anyone confirm the results?