Implementing SMS-Triggered Functions With Wireless Modem in uC/OS-II

Introduction

Integrating a USB wireless modem into an embedded system using uC/OS-II provides powerful communication capabilities. This technical article outlines a comprehensive approach to initializing a USB wireless modem, establishing AT command communication, and implementing SMS-triggered software functions.

System Architecture

The proposed system consists of the following key components:

  • USB Wireless Modem
  • Microcontroller
  • uC/OS-II Real-Time Operating System
  • Embedded Software Framework

USB Wireless Modem Initialization

Hardware Preparation

Before software implementation, ensure the following hardware connections:

  • USB wireless modem connected to microcontroller’s USB interface
  • Appropriate power supply
  • Signal and ground connections verified

Initialization Sequence

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#include "usb_modem.h"
#include "includes.h"

// USB Modem Initialization Function
INT8U InitUSBWirelessModem(void) {
    INT8U err;
    
    // Initialize USB Communication Interface
    if (USB_Init() != USB_SUCCESS) {
        return USB_INIT_ERROR;
    }
    
    // Configure Serial Communication Parameters
    SerialConfig serial_params = {
        .baud_rate = 115200,
        .data_bits = 8,
        .stop_bits = 1,
        .parity = PARITY_NONE
    };
    
    // Open Serial Port for AT Commands
    if (SerialPort_Open(&serial_params) != SERIAL_SUCCESS) {
        return SERIAL_OPEN_ERROR;
    }
    
    // Send Initial AT Commands
    if (SendATCommand("AT\r", TIMEOUT_MS) != AT_RESPONSE_OK) {
        return AT_COMMAND_ERROR;
    }
    
    // Configure SMS Mode
    if (ConfigureSMSMode() != SMS_CONFIG_SUCCESS) {
        return SMS_CONFIG_ERROR;
    }
    
    return USB_MODEM_INIT_SUCCESS;
}

// SMS Configuration Function
INT8U ConfigureSMSMode(void) {
    // Set Text Mode
    if (SendATCommand("AT+CMGF=1\r", TIMEOUT_MS) != AT_RESPONSE_OK) {
        return SMS_TEXT_MODE_ERROR;
    }
    
    // Configure SMS Storage
    if (SendATCommand("AT+CPMS=\"ME\",\"ME\",\"ME\"\r", TIMEOUT_MS) != AT_RESPONSE_OK) {
        return SMS_STORAGE_ERROR;
    }
    
    return SMS_CONFIG_SUCCESS;
}

SMS Processing Task

Task Implementation

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#define MAX_SMS_LENGTH 160
#define MAX_PHONE_NUMBER_LENGTH 20

typedef struct {
    char phone_number[MAX_PHONE_NUMBER_LENGTH];
    char message[MAX_SMS_LENGTH];
} SMSMessage;

// SMS Processing Task
void TaskSMSProcessing(void *pdata) {
    SMSMessage incoming_sms;
    INT8U err;
    
    while (1) {
        // Wait for SMS Notification
        if (WaitForSMSNotification(&incoming_sms) == SMS_RECEIVED) {
            // Process SMS Based on Content
            ProcessSMSCommand(&incoming_sms);
        }
        
        // Prevent Task Starvation
        OSTimeDlyHMSM(0, 0, 0, 100);
    }
}

// SMS Command Processing
void ProcessSMSCommand(SMSMessage *sms) {
    if (strcmp(sms->message, "SYSTEM_STATUS") == 0) {
        SendSystemStatusReport();
    }
    else if (strcmp(sms->message, "RESET_DEVICE") == 0) {
        SystemReset();
    }
    else if (strncmp(sms->message, "CONTROL_OUTPUT", 13) == 0) {
        ProcessOutputControl(sms->message);
    }
    // Additional command handlers
}

Error Handling and Robustness

Key Considerations

  • Implement comprehensive error checking
  • Use timeout mechanisms
  • Validate SMS content before processing
  • Maintain a log of SMS interactions
  • Implement security measures to prevent unauthorized commands

Performance Optimization

Recommendations

  • Use efficient memory management
  • Minimize blocking operations
  • Implement proper task prioritization
  • Use circular buffers for SMS storage
  • Optimize AT command processing

Security Considerations

  1. Implement sender authentication
  2. Use encrypted communication channels
  3. Limit and validate acceptable SMS commands
  4. Implement command access levels

Conclusion

Integrating a USB wireless modem with uC/OS-II enables sophisticated remote communication and control capabilities. By carefully implementing initialization, SMS processing, and robust error handling, developers can create powerful embedded systems with flexible remote interaction mechanisms.

References

  • uC/OS-II Reference Manual
  • USB Communication Protocols
  • AT Command Set Specifications

Note: This implementation serves as a conceptual framework and should be adapted to specific hardware and project requirements.