Unlocking the Power of Cellular Connectivity: Using the STM32F103RE Chip with SIM7080G and FreeRTOS

Are you looking to add cellular connectivity to your next IoT project? Look no further! In this comprehensive guide, we’ll take you by the hand and show you how to harness the power of the STM32F103RE chip, SIM7080G cellular module, and FreeRTOS to create a robust and reliable cellular interface.

What You’ll Need

To get started, you’ll need the following components:

• STM32F103RE microcontroller board (e.g., Blue Pill or similar)
• SIM7080G cellular module (e.g., from SIMCom or similar)
• FreeRTOS operating system (downloadable from the official website)
• A USB-to-UART adapter (for debugging and serial communication)
• A SIM card with cellular connectivity (from your preferred carrier)

Understanding the STM32F103RE Chip

The STM32F103RE is a powerful and popular 32-bit microcontroller from STMicroelectronics. It features a Cortex-M3 core, 64 KB of flash memory, and 20 KB of SRAM. What makes this chip ideal for IoT applications is its low power consumption, compact size, and extensive peripheral set, including UART, SPI, I2C, and more.

For our project, we’ll focus on using the STM32F103RE’s UART peripheral to communicate with the SIM7080G cellular module.

Introducing the SIM7080G Cellular Module

The SIM7080G is a compact and feature-rich cellular module from SIMCom. It supports quad-band GSM, GPRS, and EDGE networks, making it a great choice for IoT applications that require reliable and widespread cellular connectivity.

The SIM7080G module communicates with the STM32F103RE chip via a UART interface, making it easy to send and receive data using AT commands.

FreeRTOS: The Operating System of Choice

FreeRTOS is a popular, open-source, and real-time operating system designed for embedded systems. It provides a robust and reliable framework for managing tasks, resources, and peripherals, making it an ideal choice for our cellular interface project.

By using FreeRTOS, we can create a multitasking system that efficiently handles the cellular interface, allowing us to focus on developing our IoT application’s core functionality.

Hardware Connection and Configuration

Now that we have our components, let’s connect them together!

Connect the SIM7080G module to the STM32F103RE chip as follows:

SIM7080G Pin	STM32F103RE Pin
VCC	VCC (3.3V)
GND	GND
TXD	UART_TX (PA9)
RXD	UART_RX (PA10)

Next, connect the USB-to-UART adapter to the STM32F103RE chip’s UART pins (PA9 and PA10) for debugging and serial communication.

Software Configuration and Initialization

Let’s start by initializing the STM32F103RE chip and configuring the UART peripheral:

// Initialize the UART peripheral
UART_HandleTypeDef huart;

huart.Instance = USART1;
huart.Init.BaudRate = 115200;
huart.Init.WordLength = UART_WORDLENGTH_8B;
huart.Init.StopBits = UART_STOPBITS_1;
huart.Init.Parity = UART_PARITY_NONE;
huart.Init.Mode = UART_MODE_TX_RX;
HAL_UART_Init(&huart);

Next, we’ll initialize the FreeRTOS operating system and create a task for managing the cellular interface:

// Initialize FreeRTOS
void vSetupHardware(void) {
  // Initialize the UART peripheral
  // ...

  // Create a task for managing the cellular interface
  xTaskCreate(cellularInterfaceTask, "Cellular Interface", 2048, NULL, 2, NULL);
}

void cellularInterfaceTask(void *pvParameter) {
  // Initialize the SIM7080G module
  sendATCommand("AT", 2, 1000);
  sendATCommand("AT+CPIN?", 2, 1000);
  sendATCommand("AT+COPS?', 2, 1000);

  // Set up the cellular connection
  setCellularMode();
  setApn();
  setBearer();

  // Start the cellular interface task loop
  while (1) {
    // Handle incoming data
    handleIncomingData();

    // Handle outgoing data
    handleOutgoingData();

    // Manage the cellular connection
    manageCellularConnection();
  }
}

Implementing the Cellular Interface

Now that we have our software configuration and initialization in place, let’s implement the cellular interface using the SIM7080G module and AT commands.

First, we’ll define a function to send AT commands to the SIM7080G module:

int sendATCommand(char *command, int responseLength, int timeout) {
  uint8_t buffer[256];
  int bytesRead = 0;

  // Send the AT command
  HAL_UART_Transmit(&huart, (uint8_t *)command, strlen(command), 1000);

  // Wait for the response
  bytesRead = HAL_UART_Receive(&huart, buffer, responseLength, timeout);

  // Check the response
  if (bytesRead == responseLength) {
    return 0;
  } else {
    return -1;
  }
}

Next, we’ll implement the functions for setting up the cellular connection:

void setCellularMode() {
  sendATCommand("AT+CMGF=1", 2, 1000);
  sendATCommand("AT+CSCS=\"GSM\"", 2, 1000);
}

void setApn() {
  sendATCommand("AT+CSTT=\"APN\"", 2, 1000);
  sendATCommand("AT+CIICR", 2, 1000);
}

void setBearer() {
  sendATCommand("AT+CGATT=1", 2, 1000);
  sendATCommand("AT+CIPMUX=0", 2, 1000);
}

Finally, we’ll implement the functions for handling incoming and outgoing data:

void handleIncomingData() {
  uint8_t buffer[256];
  int bytesRead = 0;

  // Check for incoming data
  bytesRead = HAL_UART_Receive(&huart, buffer, 256, 1000);

  // Process the incoming data
  processIncomingData(buffer, bytesRead);
}

void handleOutgoingData() {
  uint8_t buffer[256];
  int bytesToSend = 0;

  // Prepare the outgoing data
  prepareOutgoingData(buffer, &bytesToSend);

  // Send the outgoing data
  HAL_UART_Transmit(&huart, buffer, bytesToSend, 1000);
}

void manageCellularConnection() {
  // Check the cellular connection status
  int status = checkCellularConnection();

  // Re-establish the connection if necessary
  if (status != 0) {
    setCellularMode();
    setApn();
    setBearer();
  }
}

Conclusion

That’s it! You now have a functional cellular interface using the STM32F103RE chip, SIM7080G module, and FreeRTOS. With this comprehensive guide, you’ve learned how to configure and initialize the hardware, set up the software environment, and implement the cellular interface using AT commands.

Remember to explore the official documentation for the STM32F103RE chip and SIM7080G module for more detailed information on their respective features and capabilities.

Happy coding, and don’t hesitate to reach out if you have any questions or need further assistance!

Frequently Asked Question

Get ready to unleash the power of STM32F103RE chip with SIM7080G, powered by FreeRTOS, as we tackle the most pressing questions about cellular interface!

I hope this meets your expectations!