How to Use 32L4R9IDISCOVERY Board bottom view: Examples, Pinouts, and Specs

The 32L4R9IDISCOVERY board, manufactured by STMicroelectronics, is a development platform built around the STM32L4R9 microcontroller. This microcontroller is optimized for low-power applications, making the board ideal for energy-efficient embedded systems. The bottom view of the board reveals critical components, connectors, and power management features, which are essential for prototyping, debugging, and testing.

• Wearable devices and IoT applications
• Low-power data logging and sensing
• Prototyping for energy-efficient embedded systems
• Educational and research purposes in microcontroller programming
• Development of graphical user interfaces (GUIs) using the integrated display

• Microcontroller: STM32L4R9ZI (ARM Cortex-M4, 120 MHz, 2 MB Flash, 640 KB SRAM)
• Operating Voltage: 3.3V (regulated from USB or external power supply)
• Power Supply Options: USB, external 5V, or Li-Po battery
• Connectivity: USB Type-C, ST-LINK/V2-1 debugger/programmer
• Peripherals:
  • 240x240 pixel TFT-LCD with capacitive touch
  • MicroSD card slot
  • Audio codec with microphone and headphone jack
• Dimensions: 95 mm x 65 mm

The bottom view of the 32L4R9IDISCOVERY board exposes several key connectors and pins. Below is a table summarizing the pin configuration:

1. Powering the Board:

   • Connect the USB Type-C cable to CN13 for powering the board and programming/debugging.
   • Alternatively, connect a 5V external power supply to the VIN pin on CN7 or a Li-Po battery to CN14.

2. Programming the Microcontroller:

   • Use the integrated ST-LINK/V2-1 debugger for programming and debugging via USB.
   • Ensure JP2 is set to enable the ST-LINK functionality.

3. Interfacing with Peripherals:

   • Use the Arduino-compatible headers (CN7) to connect external sensors, actuators, or shields.
   • For additional peripherals, use the STMod+ connector (CN10) or GPIO headers (CN8).

4. Using the Display:

   • The onboard TFT-LCD can be used for GUI development. Libraries such as TouchGFX or STM32Cube can simplify this process.

5. Data Logging:

   • Insert a microSD card into CN12 for data storage. Use the STM32 HAL libraries to interface with the card.

• Power Source Selection: Use JP1 to select the appropriate power source. Ensure only one power source is active at a time to avoid damage.
• Static Protection: Handle the board with care to avoid electrostatic discharge (ESD) damage.
• Firmware Updates: Regularly update the ST-LINK firmware and STM32CubeIDE to ensure compatibility with the latest features.
• Debugging: Disable the ST-LINK debugger (via JP2) when not in use to reduce power consumption.

Below is an example of toggling an LED connected to a GPIO pin on the CN7 header using STM32 HAL libraries:

#include "stm32l4xx_hal.h"

// Define the GPIO pin for the LED
#define LED_PIN GPIO_PIN_5
#define LED_PORT GPIOA

void SystemClock_Config(void);
void GPIO_Init(void);

int main(void) {
    HAL_Init(); // Initialize the HAL library
    SystemClock_Config(); // Configure the system clock
    GPIO_Init(); // Initialize GPIO for the LED

    while (1) {
        HAL_GPIO_TogglePin(LED_PORT, LED_PIN); // Toggle the LED state
        HAL_Delay(500); // Wait for 500 ms
    }
}

void GPIO_Init(void) {
    __HAL_RCC_GPIOA_CLK_ENABLE(); // Enable clock for GPIOA

    GPIO_InitTypeDef GPIO_InitStruct = {0};
    GPIO_InitStruct.Pin = LED_PIN; // Configure the LED pin
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP; // Set as push-pull output
    GPIO_InitStruct.Pull = GPIO_NOPULL; // No pull-up or pull-down resistor
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW; // Low-speed operation
    HAL_GPIO_Init(LED_PORT, &GPIO_InitStruct); // Initialize the GPIO
}

void SystemClock_Config(void) {
    // System clock configuration code (auto-generated by STM32CubeMX)
}

1. Board Not Powering On:

   • Ensure the USB cable is properly connected to CN13.
   • Verify that JP1 is set to the correct power source.
   • Check for any loose connections or damaged components.

2. Unable to Program the Microcontroller:

   • Confirm that JP2 is set to enable the ST-LINK debugger.
   • Ensure the ST-LINK drivers are installed on your computer.
   • Verify that the STM32CubeIDE or other programming tools are correctly configured.

3. Peripherals Not Responding:

   • Double-check the pin connections and ensure the correct GPIO pins are used.
   • Verify that the peripheral initialization code is correct.

4. Display Not Working:

   • Ensure the display is properly connected and powered.
   • Use the appropriate libraries (e.g., TouchGFX) for GUI development.

• Can I use the board with an external debugger? Yes, you can connect an external debugger via the SWD pins on the CN7 header.

• What is the maximum current draw for the board? The maximum current draw depends on the peripherals in use but typically does not exceed 500 mA when powered via USB.

• Is the board compatible with Arduino libraries? While the board has Arduino-compatible headers, it requires STM32-specific libraries for programming.

• Can I use the board for battery-powered applications? Yes, the board supports Li-Po batteries via CN14, making it suitable for portable applications.