Thingy:52 - MPU9250 Default Register Configuration

[Dan]

Hello,

I have been looking through the SDK for the Thingy:52, and I have been unable to find the configuration file used for the MPU-9250. I am able to see the default pedometer read interval, the magnetometer period, and the MPU period, but it appears as if all of the register configurations for the actual MPU come from the Bluetooth app. I have tried looking in both iOS and on Windows, and I haven't been able to see where any of these individual registers are set.

On nRF Connect, I was able to see that motion configuration has - E8 03 F4 01 F4 01 0A 00 01 written to it, but I am not sure what is specifically being written here or where it goes inside of the code. 

My goal is to be able to log motion data from the Thingy:52 (raw data, ideally), and accurately translate said data from the logging function of nRF connect.

Can you kindly point me to where I can find these configuration settings?

Best Regards,

[Simonr]

Hi Daniel

I had to ask the R&D department regarding this matter. Hopefully, I'll have an answer for you tomorrow. I'll make sure to update you as soon as I know something!

Best regards,

Simon

[Dan]

Hi Simon,

It looks like it might have been in inv_mpu.c all along under the Thingy Libraries:

* @brief Initialize hardware.
* Initial configuration:\n
* Gyro FSR: +/- 2000DPS\n
* Accel FSR +/- 2G\n
* DLPF: 42Hz\n
* FIFO rate: 50Hz\n
* Clock source: Gyro PLL\n
* FIFO: Disabled.\n
* Data ready interrupt: Disabled, active low, unlatched.
* @param[in] int_param Platform-specific parameters to interrupt API.
* @return 0 if successful.
*/

It would be good to confirm, to make sure I am not missing anything that happens after a connection. Thanks so much.

*edit -- I would also still enjoy some feedback on the configuration string I mention above. How should that be deciphered?

Dan

[Simonr]

Hi Daniel

Sorry, but it took a few days before the R&D department got around to this. But here goes:

The MPU-9250 is a multi-chip module with the MPU-6500 (accelerometer and gyrometer) and the AKM-8963 (magnetometer) combined. If you take a look at the inv_mpu.c file (note that this file is made by Invensense and not Nordic Semiconductor), you can see the following:

#elif defined MPU9250           /* #if defined MPU9150 */
#ifndef MPU6500
#define MPU6500  

This points to that when the MPU9250 is used, it uses the same configs as the MPU6500, which are located in that same file. If you need more information on how to decipher the inv_mpu files, you'll have to contact Invensense, as I can't confirm anything. The motion sensor is set up in the drv_motion.c file by us, using the inv_mpu.c files as reference.

Best regards,

Simon

[Nguyen Hoan Hoang]

This driver is a lot easier to follow. https://github.com/IOsonata/IOsonata/blob/master/src/sensors/agm_mpu9250.cpp.

The example firmware that stream data to Thingy Apps.  This firmware is made for a different board but made to be compatible with Thing App.  

https://github.com/IOsonata/IOsonata/tree/master/ARM/Nordic/exemples/BlueIOThingy