How to Use b-l475: Examples, Pinouts, and Specs

The B-L475 is a development board built around the STM32L475 microcontroller, which is part of the STM32L4 series. This microcontroller is designed for ultra-low-power applications, making the B-L475 an excellent choice for IoT (Internet of Things) projects. The board integrates various connectivity options, including Wi-Fi and Bluetooth, and features a range of onboard sensors, such as temperature, humidity, and motion sensors. These features make it ideal for prototyping smart devices, environmental monitoring systems, and wearable technology.

• IoT device prototyping
• Environmental monitoring systems
• Smart home automation
• Wearable technology
• Industrial sensor networks
• Low-power data logging systems

• Microcontroller: STM32L475VG (ARM Cortex-M4, 80 MHz, with FPU)
• Flash Memory: 1 MB
• RAM: 128 KB
• Connectivity:
  • Wi-Fi (ISM43362-M3G-L44 module)
  • Bluetooth Low Energy (BLE)
  • USB OTG
• Sensors:
  • Temperature and humidity sensor (HTS221)
  • Magnetometer and accelerometer (LSM6DSL)
  • Pressure sensor (LPS22HB)
  • Time-of-flight ranging sensor (VL53L0X)
• Power Supply: 5V via USB or external power source
• Operating Voltage: 3.3V
• Expansion: Arduino Uno V3-compatible headers, STMod+ connector
• Debugging: Integrated ST-LINK/V2-1 debugger/programmer

The B-L475 board features multiple pin headers for connectivity and expansion. Below is the pinout for the Arduino Uno V3-compatible headers:

The STMod+ connector provides additional connectivity for external modules, such as displays or communication peripherals.

1. Powering the Board:

   • Connect the board to a computer or USB power adapter using a micro-USB cable.
   • Alternatively, supply power through the VIN pin (7-12V recommended).

2. Programming the Board:

   • Install STM32CubeIDE or another compatible IDE.
   • Connect the board to your computer via USB. The integrated ST-LINK/V2-1 debugger will be detected.
   • Write your code in the IDE and upload it to the board.

3. Using Onboard Sensors:

   • The onboard sensors are connected to the STM32L475 via I2C or SPI. Use the STM32 HAL (Hardware Abstraction Layer) or LL (Low Layer) libraries to interface with them.
   • For example, the HTS221 temperature and humidity sensor can be accessed via I2C at address 0x5F.

4. Expanding Functionality:

   • Use the Arduino Uno V3-compatible headers to connect external shields or modules.
   • The STMod+ connector can be used for additional peripherals, such as displays or communication modules.

• Power Supply: Ensure the board is powered within the recommended voltage range to avoid damage.
• Debugging: Use the integrated ST-LINK/V2-1 debugger for programming and debugging. Ensure the correct drivers are installed on your computer.
• Sensor Calibration: Some onboard sensors may require calibration for accurate readings. Refer to the sensor datasheets for details.
• Low-Power Mode: To maximize battery life in IoT applications, utilize the STM32L475's low-power modes.

The B-L475 can be programmed using the Arduino IDE with the STM32 core installed. Below is an example of reading data from the onboard HTS221 temperature and humidity sensor:

#include <Wire.h>

// HTS221 I2C address
#define HTS221_ADDR 0x5F

// HTS221 register addresses
#define WHO_AM_I 0x0F
#define TEMP_OUT_L 0x2A
#define TEMP_OUT_H 0x2B

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

  // Check if HTS221 is connected
  Wire.beginTransmission(HTS221_ADDR);
  Wire.write(WHO_AM_I);
  Wire.endTransmission();
  Wire.requestFrom(HTS221_ADDR, 1);
  if (Wire.available()) {
    byte id = Wire.read();
    if (id == 0xBC) { // Expected ID for HTS221
      Serial.println("HTS221 detected!");
    } else {
      Serial.println("HTS221 not detected!");
    }
  }
}

void loop() {
  // Read temperature data
  Wire.beginTransmission(HTS221_ADDR);
  Wire.write(TEMP_OUT_L);
  Wire.endTransmission();
  Wire.requestFrom(HTS221_ADDR, 2);

  if (Wire.available() == 2) {
    int16_t temp = Wire.read() | (Wire.read() << 8);
    float temperature = temp / 256.0; // Convert to Celsius
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");
  }

  delay(1000); // Wait 1 second before next reading
}

1. Board Not Detected by Computer:

   • Ensure the USB cable is functional and supports data transfer.
   • Verify that the ST-LINK/V2-1 drivers are installed on your computer.

2. Unable to Program the Board:

   • Check that the board is in programming mode. Press the reset button if necessary.
   • Ensure the correct board and port are selected in your IDE.

3. Incorrect Sensor Readings:

   • Verify the sensor connections and I2C/SPI addresses.
   • Calibrate the sensors if required, following the datasheets.

4. Power Issues:

   • Ensure the board is powered within the recommended voltage range.
   • Check for loose connections or insufficient power supply.

• Can I use the B-L475 with Arduino shields? Yes, the board features Arduino Uno V3-compatible headers for easy integration with shields.

• Does the board support battery power? Yes, you can power the board using an external battery connected to the VIN pin.

• What IDEs are compatible with the B-L475? The board is compatible with STM32CubeIDE, Keil, IAR, and the Arduino IDE (with the STM32 core installed).

• How do I enable low-power modes? Use the STM32 HAL or LL libraries to configure the microcontroller's low-power features. Refer to the STM32L4 reference manual for details.