How to Use Flora LSM303 Compass+Accel: Examples, Pinouts, and Specs

The Flora LSM303 Compass+Accel is a compact and versatile sensor module that integrates both a 3-axis accelerometer and a 3-axis magnetometer. This sensor is designed for motion detection, orientation tracking, and magnetic field measurement, making it ideal for wearable technology, navigation systems, and gesture recognition applications.

• Wearable Devices: Integration into smartwatches, fitness trackers, and other wearable technology for activity monitoring.
• Navigation Systems: Providing heading information for handheld compasses and GPS devices.
• Gesture Recognition: Detecting movements and gestures in gaming and interactive installations.
• Robotics: Assisting in balance control and navigation for robots and drones.

• Supply Voltage: 3.3V
• Operating Current: 10 μA (low-power mode)
• Accelerometer Range: ±2/±4/±8/±16 g
• Magnetometer Range: ±1.3/±1.9/±2.5/±4.0/±4.7/±5.6/±8.1 gauss
• Communication Interface: I2C
• Operating Temperature Range: -30°C to +85°C

1. Power Connections: Connect the VCC pin to a 3.3V source and the GND pin to the ground on your microcontroller board.
2. Data Connections: Connect the SCL and SDA pins to the corresponding I2C pins on your microcontroller.
3. Initialization: Initialize the sensor using the appropriate library for your microcontroller.

• Voltage Levels: Ensure that the power supply is 3.3V, as higher voltages may damage the sensor.
• I2C Addressing: Be aware of the I2C address of the LSM303 to avoid conflicts with other I2C devices.
• Calibration: Calibrate the magnetometer for accurate readings, especially if the sensor is placed near ferrous materials.
• Library Usage: Utilize existing libraries and drivers to simplify development and ensure proper sensor operation.

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

/* Assign a unique ID to the sensors */
Adafruit_LSM303_Accel_Unified accel = Adafruit_LSM303_Accel_Unified(54321);
Adafruit_LSM303_Mag_Unified mag = Adafruit_LSM303_Mag_Unified(12345);

void setup(void) {
  Serial.begin(9600);
  Serial.println("LSM303 Accelerometer + Magnetometer Test");

  /* Initialize the sensors */
  if (!accel.begin() || !mag.begin()) {
    Serial.println("Failed to initialize the sensor(s)");
    while (1);
  }
}

void loop(void) {
  /* Get a new sensor event */
  sensors_event_t event;
  
  /* Read the accelerometer */
  accel.getEvent(&event);
  Serial.print("Accel X: "); Serial.print(event.acceleration.x); Serial.print(" ");
  Serial.print("Y: "); Serial.print(event.acceleration.y); Serial.print(" ");
  Serial.print("Z: "); Serial.print(event.acceleration.z); Serial.println(" m/s^2");

  /* Read the magnetometer */
  mag.getEvent(&event);
  Serial.print("Mag 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.println(" uT");

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

• Inaccurate Readings: If the sensor provides inaccurate readings, ensure that it is calibrated and that there are no magnetic interferences nearby.
• No Data: If the sensor does not output data, check the wiring, ensure that the correct I2C address is used, and that the sensor is properly initialized in the code.
• Intermittent Connection: Loose connections can cause intermittent data. Verify that all connections are secure.

• Calibration: Perform a calibration routine for the magnetometer to improve accuracy.
• I2C Scanning: Use an I2C scanner sketch to confirm the sensor's address and connectivity.
• Library Updates: Ensure that you are using the latest version of the sensor library.

Q: Can I use the Flora LSM303 with a 5V microcontroller? A: Yes, but ensure that the data lines are level-shifted to 3.3V to prevent damage to the sensor.

Q: How do I calibrate the magnetometer? A: Calibration typically involves rotating the sensor in several axes and using software to compute offsets. Refer to the sensor's library documentation for specific instructions.

Q: What is the default I2C address of the LSM303? A: The default I2C address for the accelerometer is 0x32 and for the magnetometer is 0x3C, but check the datasheet as addresses may vary.