Chipkit Max32 and LSM303 Magnetometer example

The LSM303 3D Accelerometers/Magnetometer Models are a system-in-package featuring a 3D digital linear acceleration sensor and a 3D digital magnetic sensor. These best-in-class eCompass devices enable superior PDR or unique use cases in emerging applications, including drones and personal navigation systems.

All full-scales available are fully selectable by the user. The device includes an I²C serial bus interface that supports standard and fast mode 100kHz and 400kHz.

Features ST is enabling more accurate personal navigation and tracking for fitness and similar apps, with a new all-in-one eCompass IC Advanced magnetic-sensing and MEMS technologies enable benchmark accuracy, with superior stability, power-saving and integration 3 magnetic field channels and 3 acceleration channels 16-bit data output SPI and/or I2C serial interfaces Analog supply voltage 2.16V to 3.6V Power-down mode / low-power mode Programmable interrupt generators for freefall, motion detection and magnetic field detection Embedded temperature sensor

Here is a picture of the module I bought

This is a schematic of a typical module such as the one above

 

Now lets look at a layout showing how to connect the module to our Arduino

 

Schematic and layout

Quite a straightforward connection being an I2C device

Code

This requires the LSM303 Adafruit to be added to the Arduino IDE via the library manager

This is the default magnetometer example

[codesyntax lang=”cpp”]

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_LSM303_U.h>

/* Assign a unique ID to this sensor at the same time */
Adafruit_LSM303_Mag_Unified mag = Adafruit_LSM303_Mag_Unified(12345);

void displaySensorDetails(void)
{
  sensor_t sensor;
  mag.getSensor(&sensor);
  Serial.println("------------------------------------");
  Serial.print  ("Sensor:       "); Serial.println(sensor.name);
  Serial.print  ("Driver Ver:   "); Serial.println(sensor.version);
  Serial.print  ("Unique ID:    "); Serial.println(sensor.sensor_id);
  Serial.print  ("Max Value:    "); Serial.print(sensor.max_value); Serial.println(" uT");
  Serial.print  ("Min Value:    "); Serial.print(sensor.min_value); Serial.println(" uT");
  Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println(" uT");
  Serial.println("------------------------------------");
  Serial.println("");
  delay(500);
}

void setup(void)
{
#ifndef ESP8266
  while (!Serial);     // will pause Zero, Leonardo, etc until serial console opens
#endif
  Serial.begin(9600);
  Serial.println("Magnetometer Test"); Serial.println("");

  /* Enable auto-gain */
  mag.enableAutoRange(true);

  /* Initialise the sensor */
  if(!mag.begin())
  {
    /* There was a problem detecting the LSM303 ... check your connections */
    Serial.println("Ooops, no LSM303 detected ... Check your wiring!");
    while(1);
  }

  /* Display some basic information on this sensor */
  displaySensorDetails();
}

void loop(void)
{
  /* Get a new sensor event */
  sensors_event_t event;
  mag.getEvent(&event);

  /* Display the results (magnetic vector values are in micro-Tesla (uT)) */
  Serial.print("X: "); Serial.print(event.magnetic.x); Serial.print("  ");
  Serial.print("Y: "); Serial.print(event.magnetic.y); Serial.print("  ");
  Serial.print("Z: "); Serial.print(event.magnetic.z); Serial.print("  ");Serial.println("uT");

  /* Note: You can also get the raw (non unified values) for */
  /* the last data sample as follows. The .getEvent call populates */
  /* the raw values used below. */
  // Serial.print("X Raw: "); Serial.print(mag.raw.x); Serial.print("  ");
  // Serial.print("Y Raw: "); Serial.print(mag.raw.y); Serial.print("  ");
  // Serial.print("Z Raw: "); Serial.print(mag.raw.z); Serial.println("");

  /* Delay before the next sample */
  delay(500);
}

[/codesyntax]

Testing

Open the Serial Monitor window and you should see something like this

Magnetometer Test

————————————
Sensor: LSM303
Driver Ver: 1
Unique ID: 12345
Max Value: 0.00 uT
Min Value: 0.00 uT
Resolution: 0.00 uT
————————————

X: -15.73 Y: -20.00 Z: 40.31 uT
X: -15.82 Y: -20.27 Z: 40.61 uT
X: -15.91 Y: -20.36 Z: 40.82 uT
X: -15.45 Y: -20.09 Z: 40.51 uT
X: -6.91 Y: -9.64 Z: 56.33 uT
X: 6.18 Y: 28.36 Z: 69.39 uT
X: 10.55 Y: 48.55 Z: 62.35 uT
X: 34.64 Y: -15.45 Z: 45.41 uT
X: -21.55 Y: -0.09 Z: 54.29 uT
X: -16.73 Y: -12.82 Z: 48.88 uT

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