Hi,
I'm pretty new here so sorry if my mistake is too obvious..
I am learning about the sensor MPU9250 Acc & Gyro & Magnetometer.
I want to know how to get the raw data straight from the registers instead of using a library..
I manage to read the raw data from the registers of the accelerometer and gyro and convert them into the correct values in the units I wanted, so the accelerometer and gyro work good for me.
The problem is when I read the raw data from the Magnetometer registers.
it was quite a headache at the start just to communicate with the magnetometer but I manage to do it eventually after finding out that I need to turn the bypass.
After I did it I got the right values from the Device ID register (0x00) I also set the CONTROL 1 register into Fuse ROM Access Mode, got the adjustment sensitivity values for each axis, turned the CONTROL 1 into Sleep Mode and then into Continuous Measurement Mode 2 (I saw at some post that someone said after getting into Fuse ROM Mode you need to go to Sleep Mode before changing to any other mode)
The problem is this: I get the raw register data, convert it to MicroTesla(uT) units but the values seem to be too low. I read that earth magnetic field is somewhere between 20-65 uT and I get read between the values -3 and +3.. I searched everywhere at the internet but couldn't find why it doesn't work for me and where is my mistake. I think maybe it has something to do with the types I chose for the parameters but I got no idea why it's wrong..
anyone got an idea what is wrong?
I think it's important to say that I also used SpearkFun library just to check that the sensor is alright and when I used SparkFun library the values of the magnetometer were good.
I tried to find all over the internet the full code of this library (and also for Kriswiner library because I read that the SparkFun library is based on this) but no where to find the full code, I found some parts of the code but always the part I needed was not public..
Anyone know what is wrong? I am really lost over here..
I am adding my full code here + results from the serial monitor
Thanks a lot for reading this
My Code:
#include "Wire.h"
const int MPU_ADDR = 0x68; // 0x say that we are working with hex numbers and 68 is the acc & gyro sensor adress in hex (from data sheet)
const int MAG_ADDR = 0x0C; // 0x say that we are working with hex numbers and 0C is the magnetometer sensor adress in hex (from data sheet)
int8_t Device_ID;
int8_t mag_xL, mag_xH, mag_yL, mag_yH, mag_zL, mag_zH;
int16_t mag_x, mag_y, mag_z;
int16_t acc_x, acc_y, acc_z;
int16_t gyr_x, gyr_y, gyr_z;
int16_t temp;
int8_t Msens_x,Msens_y, Msens_z;
int8_t control_1;
int8_t status_1;
int8_t status_2;
float Yaw;
float asax, asay, asaz;
void setup() {
Serial.begin(9600);
Wire.begin();
// Acc & Gyro Registers********************************************
Wire.beginTransmission(MPU_ADDR);
Wire.write(0x6A); // USER CONTROL
Wire.write(0x00); // 0x00 is reset value
Wire.endTransmission(true);
Wire.beginTransmission(MPU_ADDR);
Wire.write(0x37); // IMU INT PIN CONFIG
Wire.write(0x02); // 0x02 activate bypass in order to communicate with magnetometer
Wire.endTransmission(true);
delay(200);
// Magnetometer Registers*****************************************
Wire.beginTransmission(MAG_ADDR);
Wire.write(0x0B); // CONTROL 2
Wire.write(0b01); // 0 NORMAL OR 1 RESET
Wire.endTransmission(true);
delay(200);
Wire.beginTransmission(MAG_ADDR); //SLEEP MODE
Wire.write(0x0A); // CONTROL 1
Wire.write(0b00010000); // 1 for 16 bit or 0 for 14 bit output, 0000 SLEEP MODE
Wire.endTransmission(true);
delay(200);
Wire.beginTransmission(MAG_ADDR); //ROM WRITE MODE
Wire.write(0x0A); // CONTROL 1
Wire.write(0b00011111); // 1 for 16 bit or 0 for 14 bit output, 1111 FUSE ROM ACCESS MODE
Wire.endTransmission(true);
delay(200);
Wire.beginTransmission(MAG_ADDR); //GET MAGNETIC SENSITIVITY DATA FOR CONVERTING RAW DATA
Wire.write(0x10); // ASAX
Wire.endTransmission(false);
Wire.requestFrom(MAG_ADDR, 3 , true); //GET SENSITIVITY ADJUSMENT VALUES STARTS AT ASAX
Msens_x = Wire.read(); //GET X SENSITIVITY ADJUSMENT VALUE
Msens_y = Wire.read(); //GET Y SENSITIVITY ADJUSMENT VALUE
Msens_z = Wire.read(); //GET Z SENSITIVITY ADJUSMENT VALUE
Serial.println(Msens_x);
Serial.println(Msens_y);
Serial.println(Msens_z);
Wire.endTransmission(true);
asax = (((Msens_x-128))/256.0f)+1.0f;
asay = (((Msens_y-128))/256.0f)+1.0f;
asaz = (((Msens_z-128))/256.0f)+1.0f;
Serial.print("Mx Sensitivity: "); Serial.println(asax);
Serial.print("My Sensitivity: "); Serial.println(asay);
Serial.print("Mz Sensitivity: "); Serial.println(asaz);
delay(200);
Wire.beginTransmission(MAG_ADDR); //SLEEP MODE
Wire.write(0x0A); // CONTROL 1
Wire.write(0b00010000); // 1 for 16 bit or 0 for 14 bit output, 0000 SLEEP MODE
Wire.endTransmission(true);
delay(200);
Wire.beginTransmission(MAG_ADDR); //CONT MODE 2
Wire.write(0x0A);
Wire.write(0b00010110); // 1 for 16 bit or 0 for 14 bit output, 0110 FOR CONT MODE 2 (X Hz?)
Wire.endTransmission(true);
delay(200);
}
void loop() {
Wire.beginTransmission(MAG_ADDR);
Wire.write(0x00);
Wire.endTransmission(false);
Wire.requestFrom(MAG_ADDR, 1 , true);
Device_ID = Wire.read();
Serial.print("Device_ID: "); Serial.println(Device_ID,DEC);
Wire.endTransmission(true);
Wire.beginTransmission(MAG_ADDR);
Wire.write(0x0A);
Wire.endTransmission(false);
Wire.requestFrom(MAG_ADDR, 1 , true);
control_1 = Wire.read(); // check DRDY bit if ready to read
Serial.print("control_1: "); Serial.println(control_1,BIN);
Wire.endTransmission(true);
Wire.beginTransmission(MAG_ADDR);
Wire.write(0x02);
Wire.endTransmission(false);
Wire.requestFrom(MAG_ADDR, 1 , true);
status_1 = Wire.read();
Serial.print("Status 1: "); Serial.println(status_1,BIN);
Wire.endTransmission(true);
if(status_1 == 0b11) {
Wire.beginTransmission(MAG_ADDR);
Wire.write(0x03);
Wire.endTransmission(false);
Wire.requestFrom(MAG_ADDR, 7 , true);
mag_xL = Wire.read();
mag_xH = Wire.read();
mag_x = (mag_xH << 8) | mag_xL;
Serial.print("Available bytes left after reading mag x values: "); Serial.println(Wire.available(),DEC);
mag_yL = Wire.read();
mag_yH = Wire.read();
mag_y = (mag_yH << 8) | mag_yL;
Serial.print("LOW BITS Mag_Y: "); Serial.println(mag_yL,BIN);
Serial.print("HIGH BITS Mag_Y: "); Serial.println(mag_yH,BIN);
Serial.print("FULL BITS Mag_Y: "); Serial.println(mag_y,BIN);
mag_zL = Wire.read();
mag_zH = Wire.read();
mag_z = (mag_zH << 8) | mag_zL;
status_2 = Wire.read(); // check if there is a magnetic overflow
Serial.print("Status 2: "); Serial.println(status_2,BIN);
//if(status_2 != 0x08)
Wire.endTransmission(true);
Serial.print(" | mX = "); Serial.print(mag_x*asax*0.15); Serial.print(" [uT]");
Serial.print(" | mY = "); Serial.print(mag_y*asay*0.15); Serial.print(" [uT]");
Serial.print(" | mZ = "); Serial.print(mag_z*asaz*0.15); Serial.println(" [uT]");
}
// Yaw = (atan2(mag_y,mag_x)*(180/3.141));
//Serial.println(Yaw);
Serial.println("-------------------------------END OF THE LOOP ---------------------------");
delay(500);
}
Results are added in a picture because I couldn't copy it for some reason
I was rotating the sensor while doing the measurements.
I have also added my code in a file so it will be maybe easier to see it
aaa.ino (5.36 KB)
