MPU on raspberry pi 4

[zoldaten]

hi!
thanks Gods i have implemented MPU on raspberry pi 4 raspbian with ROS noetic and
everything works perfects with vpython example.
i plan to use MPU with ORB_SLAM3.

here`s my steps if someone want to follow:

*http://wiki.ros.org/razor_imu_9dof
pip3 install --upgrade pip
pip3 install cryptography==3.4.6
pip3 install vpython

cd catkin_ws/src
git clone https://github.com/ENSTABretagneRobotics/razor_imu_9dof.git
source /home/pi/catkin_ws/devel/setup.bash
cd .. &&  catkin_make
cd src/razor_imu_9dof/nodes
wget https://www.glowscript.org/docs/VPythonDocs/VPtoGS.py ; python3 VPtoGS.py ; cp -f Converted/display_3D_visualization.py display_3D_visualization.py ; cd ../../..
roscd razor_imu_9dof/config
cp razor.yaml my_razor.yaml
*find MPU on USB ports:
dmesg | grep tty

*https://learn.sparkfun.com/tutorials/9dof-razor-imu-m0-hookup-guide/all
install arduino ide 1.8.18
put to preferences:
	https://raw.githubusercontent.com/sparkfun/Arduino_Boards/master/IDE_Board_Manager/package_sparkfun_index.json

Board Manager -> SparkFun SAMD Boards-> install
roscd razor_imu_9dof
cp -r src/Razor_AHRS ~/Arduino
select SparkFun 9DoF Razor IMU M0 to upload
uncomment in Razor_AHRS.ino:
	#define HW__VERSION_CODE 14001 // SparkFun "9DoF Razor IMU M0" version "SEN-14001"
upload Razor_AHRS.ino

test:
roslaunch razor_imu_9dof razor-pub-and-display.launch
or 
roslaunch razor_imu_9dof razor-pub.launch

But i have some questions:
1.
how to set frequency of MPU ?
i have change my_razor.yaml:
pub_rate: 200.0
is that the way?
2.
how to understand axis on the board ?
i saw X and Y arrows of MAG and GYRO. they are in different directions. and what about Z ? crossed cirlce means FACE UP or DOWN ?

could you help a bit ?