IoT Modem Modules: Practical Selection Guide

// Basic IoT Modem Connection Example
// Compatible with most Quectel, SIMCom modules

#include 

// Create a SoftwareSerial object for modem communication
SoftwareSerial modem(7, 8); // RX, TX pins

// Configuration
const char* apn = "iot.1nz.co.nz";  // Replace with your carrier's IoT APN
const int timeout = 10000; // Command timeout in milliseconds

void setup() {
  Serial.begin(9600);
  modem.begin(9600);
  
  Serial.println("IoT Modem Setup Starting...");
  delay(3000); // Allow modem to initialize
  
  // Test modem communication
  if (sendATCommand("AT", "OK", 5000)) {
    Serial.println("Modem communication established");
  } else {
    Serial.println("ERROR: Cannot communicate with modem");
    return;
  }
  
  // Check signal quality
  sendATCommand("AT+CSQ", "OK", 5000);
  
  // Set APN
  String apnCommand = "AT+CGDCONT=1,\"IP\",\"" + String(apn) + "\"";
  sendATCommand(apnCommand.c_str(), "OK", 5000);
  
  // Attach to network
  sendATCommand("AT+CGATT=1", "OK", 30000);
  
  // Activate PDP context
  sendATCommand("AT+CGACT=1,1", "OK", 30000);
  
  Serial.println("Modem setup complete!");
}

void loop() {
  // Example: Send HTTP GET request
  if (sendHTTPRequest()) {
    Serial.println("Data sent successfully");
  } else {
    Serial.println("Failed to send data");
  }
  
  delay(60000); // Wait 1 minute before next transmission
}

bool sendATCommand(const char* command, const char* expectedResponse, unsigned long timeout) {
  Serial.print("Sending: ");
  Serial.println(command);
  
  modem.println(command);
  
  String response = "";
  unsigned long startTime = millis();
  
  while (millis() - startTime < timeout) {
    if (modem.available()) {
      char c = modem.read();
      response += c;
      
      if (response.indexOf(expectedResponse) != -1) {
        Serial.print("Response: ");
        Serial.println(response);
        return true;
      }
      
      if (response.indexOf("ERROR") != -1) {
        Serial.print("Error Response: ");
        Serial.println(response);
        return false;
      }
    }
  }
  
  Serial.println("Command timeout");
  return false;
}

bool sendHTTPRequest() {
  // Initialize HTTP service
  if (!sendATCommand("AT+HTTPINIT", "OK", 5000)) return false;
  
  // Set HTTP parameters
  if (!sendATCommand("AT+HTTPPARA=\"CID\",1", "OK", 5000)) return false;
  if (!sendATCommand("AT+HTTPPARA=\"URL\",\"http://httpbin.org/get\"", "OK", 5000)) return false;
  
  // Send GET request
  if (!sendATCommand("AT+HTTPACTION=0", "OK", 30000)) {
    sendATCommand("AT+HTTPTERM", "OK", 5000);
    return false;
  }
  
  // Read response
  sendATCommand("AT+HTTPREAD", "OK", 5000);
  
  // Terminate HTTP service
  sendATCommand("AT+HTTPTERM", "OK", 5000);
  
  return true;
}