How to Use BMI323: Examples, Pinouts, and Specs

The BMI323 is a 3-axis digital accelerometer and gyroscope sensor manufactured by Bosch. It is designed for motion tracking applications, offering high precision measurements of angular velocity and acceleration. This sensor is ideal for use in smartphones, wearables, gaming devices, and other IoT applications requiring accurate motion detection and orientation tracking.

• Motion tracking in smartphones and tablets
• Fitness and health monitoring in wearables
• Gesture recognition in gaming devices
• Robotics and drone navigation
• Industrial IoT for vibration and motion analysis

The BMI323 combines a 3-axis accelerometer and a 3-axis gyroscope in a compact package. Below are the key technical details:

The BMI323 is available in a 12-pin LGA package. Below is the pin configuration:

1. Power Supply: Connect the VDD pin to a 1.71V to 3.6V power source and the VDDIO pin to the desired I/O voltage (1.2V to 3.6V). Connect all GND pins to the ground.
2. Communication Interface: Choose between I²C or SPI for communication:
   • For I²C, connect the SCL and SDA pins to the corresponding I²C lines on your microcontroller. Use pull-up resistors (typically 4.7 kΩ) on both lines.
   • For SPI, connect the CS, SCL, SDA, and SDO pins to the corresponding SPI lines on your microcontroller.
3. Interrupts: Use the INT1 and INT2 pins to configure and handle interrupts for motion detection or other events.
4. Initialization: Configure the sensor's registers via the chosen communication interface to set the desired measurement range, output data rate, and other parameters.

• Bypass Unused Pins: Leave NC pins unconnected.
• Decoupling Capacitors: Place a 0.1 µF decoupling capacitor close to the VDD and VDDIO pins to reduce noise.
• I²C Address: The I²C address of the BMI323 is determined by the CS pin. Pulling CS low sets the address to 0x68, while pulling it high sets it to 0x69.
• Orientation: Ensure the sensor is mounted correctly to align with the desired axes of measurement.

Below is an example of how to interface the BMI323 with an Arduino UNO using I²C:

#include <Wire.h>

#define BMI323_I2C_ADDRESS 0x68 // Default I²C address when CS is low

// BMI323 register addresses
#define BMI323_CHIP_ID_REG 0x00
#define BMI323_ACCEL_X_LSB 0x12

void setup() {
  Wire.begin(); // Initialize I²C communication
  Serial.begin(9600); // Initialize serial communication for debugging

  // Check BMI323 connection
  Wire.beginTransmission(BMI323_I2C_ADDRESS);
  Wire.write(BMI323_CHIP_ID_REG); // Request chip ID register
  Wire.endTransmission();
  Wire.requestFrom(BMI323_I2C_ADDRESS, 1);

  if (Wire.available()) {
    uint8_t chipID = Wire.read();
    if (chipID == 0x33) { // Expected chip ID for BMI323
      Serial.println("BMI323 detected!");
    } else {
      Serial.println("BMI323 not detected. Check connections.");
    }
  }
}

void loop() {
  // Read accelerometer X-axis data
  Wire.beginTransmission(BMI323_I2C_ADDRESS);
  Wire.write(BMI323_ACCEL_X_LSB); // Request X-axis LSB register
  Wire.endTransmission();
  Wire.requestFrom(BMI323_I2C_ADDRESS, 2); // Read 2 bytes (LSB + MSB)

  if (Wire.available() == 2) {
    int16_t accelX = Wire.read(); // Read LSB
    accelX |= (Wire.read() << 8); // Read MSB and combine
    Serial.print("Accel X: ");
    Serial.println(accelX);
  }

  delay(100); // Delay for readability
}

1. Sensor Not Detected:

   • Ensure the I²C address matches the configuration of the CS pin.
   • Check the wiring and ensure pull-up resistors are used on the I²C lines.
   • Verify the power supply voltage is within the specified range.

2. Incorrect Readings:

   • Confirm the sensor is properly mounted and aligned with the desired axes.
   • Check the configuration of the measurement range and output data rate.

3. No Interrupts Triggered:

   • Verify the interrupt pins (INT1/INT2) are properly connected to the microcontroller.
   • Ensure the interrupt registers are correctly configured.

• Use an oscilloscope or logic analyzer to verify I²C or SPI communication.
• Check for noise or instability in the power supply and add additional filtering if needed.
• Refer to the BMI323 datasheet for detailed register descriptions and configuration options.