Using MPU9250BasicAHRS with Arduino

[CJRud]

Hi there,

In your description you say that this code is an Arduino Sketch. I'm fairly new to coding with Arduino and would love to use your libraries/ code to get fused sensor data coming out of my MPU9250 to be logged onto an SD card.

For the time being, I'm taking one step at a time and just want to see the fused sensor values in my serial monitor without any SD card functionality. I am using just an Arduino Uno R3 and MPU9250 breakout from Drotek, see link below, but no Adafruit display that is described in the "MPU9250BasicAHRS.ino" file description. When I run the "MPU9250BasicAHRS.ino" there are obvious problems associated with the fact that I don't have the display libraries/ LCD attached. It won't compile. The MPU9250 I have is on the default I2C bus address 0x68 and is recognised when running an I2C scanner.

I'd like all the functionality you described in the starting comments: "Demonstrate basic MPU-9250 functionality including parameterizing the register addresses, initializing the sensor,
getting properly scaled accelerometer, gyroscope, and magnetometer data out. Addition of 9 DoF sensor fusion using open source Madgwick and Mahony filter algorithms", just without the LCD display. How do I do this? The DMP values I'm particularly interested in having are world frame acceleration in x,y,z and absolute Euler angles for yaw pitch roll, if this is possible.

Could you give any advice (quick step-by-step perhaps) or adapted code that can get this functionality using what I have? I assume it isn't as simple as commenting/ deleting all the calls to the LCD display/libraries? Hopefully your experience can help me out here!

Secondly, I'd like to sample my accel, gyro and mag at a fairly low 25 Hz. Looking through the code I found a number of comments talking about setting sample rates for each accel, gyro, mag and temp sensors but was confused as to exactly how to do this. There's a lot of code here and I don't want to change something somewhere and have it mess up everything else. How do I do this?

If you also have any comments about the feasibility of saving these values to an SD card at 25Hz then I'd be happy to hear them. I'm using the Adafruit datalogging SD card shield, see link below. I tried a while ago to save from an MPU6050 using DMP to an SD card and the FIFO buffer didn't like it, it kept overflowing and everything was very slow. I resorted then to saving only raw sensor values, which worked very well, but I really want to use the fused values for this latest project.

Any advice welcomed! Thank you in advance, looking forward to hearing your comments.

Best,
Chris

Drotek sensor (assembled for I2C):
http://www.drotek.com/shop/en/home/421-mpu9250-gyro-accelerometer-magnetometer.html?search_query=mpu9250&results=3

Adafruit SD shield:
https://www.adafruit.com/products/1141

[kriswiner]

Hi Chris,

If you are not using the display, then yes remove all of the reference to
it.

Also, the I2C functions are set up to use the i2C_t3.h library for the
Teensy (which I highly recommend). If you want to use Wire.h on the UNO you
will need to make some modifications on the wire.begin and wire.readByte,
etc functions. The Wire.h versions are commented out in those function,
shouldn't be too hard to figure out.

If you want to understand how to change the data rates you are going to have
to read the data sheet; I would recommend this anyway if you are going to
use this sensor well.

Once you get these issues sorted out, the code will produce fused yaw,
pitch, and roll as well as quaternions for you to spew to the serial
monitor. After that, writing to an SD card is easy.

Kris

-----Original Message-----
From: CJRud [mailto:notifications@github.com]
Sent: December 11, 2015 8:25 AM
To: kriswiner/MPU-9250
Subject: [MPU-9250] Using MPU9250BasicAHRS with Arduino (#36)

Hi there,

In your description you say that this code is an Arduino Sketch I'm fairly
new to coding with Arduino and would love to use your libraries/ code to get
fused sensor data coming out of my MPU9250 to be logged onto an SD card

For the time being, I'm taking one step at a time and just want to see the
fused sensor values in my serial monitor without any SD card functionality I
am using just an Arduino Uno R3 and MPU9250 breakout from Drotek, see link
below, but no Adafruit display that is described in the
"MPU9250BasicAHRSino" file description When I run the "MPU9250BasicAHRSino"
there are obvious problems associated with the fact that I don't have the
display libraries/ LCD attached It won't compile The MPU9250 I have is on
the default I2C bus address 0x68 and is recognised when running an I2C
scanner

I'd like all the functionality you described in the starting comments:
"Demonstrate basic MPU-9250 functionality including parameterizing the
register addresses, initializing the sensor,
getting properly scaled accelerometer, gyroscope, and magnetometer data out
Addition of 9 DoF sensor fusion using open source Madgwick and Mahony filter
algorithms", just without the LCD display How do I do this?

Could you give any advice (quick step-by-step perhaps) or adapted code that
can get this functionality using what I have? I assume it isn't as simple as
commenting/ deleting all the calls to the LCD display/libraries? Hopefully
your experience can help me out here!

Secondly, I'd like to sample my accel, gyro and mag at a fairly low 25 Hz
Looking through the code I found a number of comments talking about setting
sample rates for each accel, gyro, mag and temp sensors but was confused as
to exactly how to do this There's a lot of code here and I don't want to
change something somewhere and have it mess up everything else How do I do
this?

If you also have any comments about the feasibility of saving these values
to an SD card at 25Hz then I'd be happy to hear them I'm using the Adafruit
datalogging SD card shield, see link below I tried a while ago to save from
an MPU6050 using DMP to an SD card and the FIFO buffer didn't like it, it
kept overflowing and everything was very slow I resorted then to saving only
raw sensor values, which worked very well, but I really want to use the
fused values for this latest project

Any advice welcomed! Thank you in advance, looking forward to hearing your
comments

Best,
Chris

Drotek sensor (assembled for I2C):
http://wwwdrotekcom/shop/en/home/421-mpu9250-gyro-accelerometer-magnetometer
html?search_query=mpu9250&results=3

Adafruit SD shield:
https://wwwadafruitcom/products/1141

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[andresespinosapc]

@CJRud could you make it work? I also want to use an Arduino UNO, just because I already have it. I don't care if it could work better, I just want it to work.

@kriswiner I don't understand why should we modify the Wire.h if you specify in the MPU9250_MS5637_AHRS_t3.ino file that the "Sketch runs on the 3.3 V 8 MHz Pro Mini". If it works for that Arduino, why does it not work for the Arduino UNO?

[kriswiner]

The _t3 means it uses the Teensy-specific i2c_t3.h wire library.

-----Original Message-----
From: Andres Espinosa [mailto:notifications@github.com]
Sent: October 10, 2016 2:47 PM
To: kriswiner/MPU-9250
Cc: Kris Winer; Mention
Subject: Re: [kriswiner/MPU-9250] Using MPU9250BasicAHRS with Arduino (#36)

@CJRud https://github.com/CJRud could you make it work? I also want to
use an Arduino UNO, just because I already have it. I don't care if it could
work better, I just want it to work.

@kriswiner https://github.com/kriswiner I don't understand why should we
modify the Wire.h if you specify in the MPU9250_MS5637_AHRS_t3.ino file that
the "Sketch runs on the 3.3 V 8 MHz Pro Mini". If it works for that Arduino,
why does it not work for the Arduino UNO?

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