micro:bit and MLX90393 magnetic field sensor example

The MLX90393 magnetic field sensor can be reprogrammed to different modes and with different settings at run-time. The sensor offers a 16-bit output proportional to the magnetic flux density sensed along the XYZ axes using the Melexis proprietary Triaxis® technology and also offers a temperature output signal. These digital values are available via I2C and SPI, where the MLX90393 is a slave on the bus.

By selecting which axes are to be measured, the raw data can be used as input for further post-processing, such as for joystick applications, rotary knobs, and more complex 3D position sensing applications. Unparallelled performance is achieved with this sensor, which is primarily targeting industrial and consumer applications.

Connection

Code

[codesyntax lang=”cpp”]

#include<Wire.h>

// MLX90393 I2C Address is 0x0C(12)
#define Addr 0x0C

void setup() 
{
// Initialise I2C communication as MASTER 
Wire.begin();
// Initialise serial communication, set baud rate = 9600
Serial.begin(9600);

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select Write register command
Wire.write(0x60);
// Set AH = 0x00, BIST disabled
Wire.write((float)0x00);
// Set AL = 0x5C, Hall plate spinning rate = DEFAULT, GAIN_SEL = 5 
Wire.write(0x5C);
// Select address register, (0x00 << 2)
Wire.write((float)0x00);
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read status byte
if(Wire.available() == 1) 
{
unsigned int c = Wire.read();
}

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select Write register command
Wire.write(0x60);
// Set AH = 0x02
Wire.write(0x02);
// Set AL = 0xB4, RES for magnetic measurement = 0
Wire.write(0xB4);
// Select address register, (0x02 << 2)
Wire.write(0x08);
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read status byte
if(Wire.available() == 1) 
{
unsigned int c = Wire.read();
}
delay(300);
}

void loop() 
{
unsigned int data[7];

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Start single meaurement mode, ZYX enabled
Wire.write(0x3E);
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read status byte
if(Wire.available() == 1) 
{
unsigned int c = Wire.read();
}
delay(100);

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Send read measurement command, ZYX enabled
Wire.write(0x4E);
// Stop I2C Transmission
Wire.endTransmission();

// Request 7 bytes of data
Wire.requestFrom(Addr, 7);

// Read 7 bytes of data
// status, xMag msb, xMag lsb, yMag msb, yMag lsb, zMag msb, zMag lsb
if(Wire.available() == 7);
{
data[0] = Wire.read();
data[1] = Wire.read();
data[2] = Wire.read();
data[3] = Wire.read();
data[4] = Wire.read();
data[5] = Wire.read();
data[6] = Wire.read();
}

// Convert the data
int xMag = data[1] * 256 + data[2];
int yMag = data[3] * 256 + data[4];
int zMag = data[5] * 256 + data[6];

// Output data to serial monitor
Serial.print("Magnetic Field in X-Axis : ");
Serial.println(xMag);
Serial.print("Magnetic Field in Y-Axis : ");
Serial.println(yMag);
Serial.print("Magnetic Field in Z-Axis : ");
Serial.println(zMag);
delay(500);
}

[/codesyntax]

Output

Open the serial monitor and you should see something like this

Magnetic Field in X-Axis : 66
Magnetic Field in Y-Axis : 65458
Magnetic Field in Z-Axis : 8
Magnetic Field in X-Axis : 83
Magnetic Field in Y-Axis : 65477
Magnetic Field in Z-Axis : 65525
Magnetic Field in X-Axis : 76
Magnetic Field in Y-Axis : 65452
Magnetic Field in Z-Axis : 65506
Magnetic Field in X-Axis : 25
Magnetic Field in Y-Axis : 65374
Magnetic Field in Z-Axis : 65512
Magnetic Field in X-Axis : 80

Links

https://www.melexis.com/-/media/files/documents/datasheets/mlx90393-datasheet-melexis.pdf
CJMCU-90393, MLX90393 digital 3D Holzer sensor, displacement, angle, rotation, 3D position