File content as of revision 1:450535d62644:

#include "mbed.h"
#include <iostream>
#include <string>
#include "DFRobot_SIM7000.h"

#define server_ip "140.114.78.140" //140.114.89.66 //140.114.78.140
#define PORT 1883 //TCP: 3307 //MQTT: 1883
#define CLIENT_ID  ""
#define USERNAME  "delta"
#define PASSWORD  "delta"
#define SUBSCRIBE_TOPIC_PREFIX  "nbiot/"
#define PUBLISH_TOPIC  "nbiot/gw"

DFRobot_SIM7000    sim7000;
DigitalOut myled(LED1);

Serial pc(USBTX, USBRX, 9600);
Serial nbiot_shield(PA_9, PA_10, 19200); //(tx,rx,baud) 

char IMSI[20];
string str_IMSI;
char *cTopic;
 
void PC_callback() { //useless now
    // Note: you need to actually read from the serial to clear the RX interrupt
    // nbiot_shield.putc(pc.getc());
    char cmd[20];
    pc.gets(cmd, 20);
    pc.printf("Command from PC: %s", cmd);
    nbiot_shield.printf(cmd);
} 
void NBIOT_callback() { //useless now
    //pc.printf("NBIOT_callback\r\n");
    //pc.putc(nbiot_shield.getc());
    
    char msg[20];
    nbiot_shield.gets(msg, 20);
    pc.printf("Message from SIM: %s", msg);
}


void connect_to_server(){
    printf("Connecting to the server %s......\r\n", server_ip);
    while(1){
      if(sim7000.openNetwork(TCP,server_ip,PORT)){           //Start up TCP connection //TCP: 3307 //MQTT: 1883
          printf("Connect OK\r\n");
          break;
      }else{
          printf("Fail to connect\r\n");
          wait(10);
      }
    }
  
    printf("Connecting to the MQTT......\r\n");
    if(sim7000.mqttConnect(IMSI,USERNAME,PASSWORD)){    //MQTT connect request
        printf("OK\r\n");
    }else{
        printf("Failed\r\n");
        //return;
    }
    
    string topic = SUBSCRIBE_TOPIC_PREFIX + str_IMSI.substr(5); //first 5 number are fixed
    
    cTopic = new char[topic.length() + 1];
    strcpy(cTopic, topic.c_str());
    printf("Subscribe to the MQTT Topic %s......\r\n", cTopic);
    if(sim7000.mqttSubscribe(cTopic)){  
        printf("OK\r\n");
    }else{
        printf("Failed\r\n");
        //return;
    }
    
}

 
int main() {
    millisStart();
    
    sim7000.begin(nbiot_shield);
    
    printf("Turn ON SIM7000......\r\n");
    if(sim7000.turnON()){                             //Turn ON SIM7000
        printf("Turn ON !\r\n");
    }
    
    printf("Set baud rate......\r\n");
    while(1){
        if(sim7000.setBaudRate(19200)){               //Set SIM7000 baud rate from 115200 to 19200 reduce the baud rate to avoid distortion
            printf("Set baud rate:19200\r\n");
            break;
        }else{
            printf("Faile to set baud rate\r\n");
            wait(1);
        }
    }
    
    printf("Set the APN......\r\n");
    while(1){
        if (sim7000.check_send_cmd("AT+CSTT=\"internet.iot\"\r\n","OK")){
          printf("OK\r\n");
          break;
        }
        else{
          printf("Faile to set the APN\r\n");
          wait_ms(1000);
        }
    }

    printf("Bring Up Wireless Connection with GPRS......\r\n");
    while(1){
        if(sim7000.check_send_cmd("AT+CIICR\r\n","OK")){ 
            printf("Successfully\r\n");
            break;
        }else{
            printf("Faile to bring Up Wireless Connection with GPRS\r\n");
            wait_ms(1000);
        }
    }

    printf("Get local IP address......\r\n");
    char gprsBuffer[32];
    while(1){
        sim7000.cleanBuffer(gprsBuffer,32);
        sim7000.send_cmd("AT+CIFSR\r\n");
        sim7000.readBuffer(gprsBuffer, 32, DEFAULT_TIMEOUT);
        
        if(NULL != strstr(gprsBuffer, "ERROR")){
            printf("Faile to Get local IP address\r\n");
            wait_ms(1000);
        }
        else{
          //strcpy(local_IP, gprsBuffer+strlen("AT+CIFSR\r\n")+1);  //implement issue here
          printf("OK\r\n");
          break;
        }
    }

    printf("Get IMSI......\r\n");
    while(1){
        sim7000.cleanBuffer(gprsBuffer,32);
        sim7000.send_cmd("AT+CIMI\r\n");
        sim7000.readBuffer(gprsBuffer, 32, DEFAULT_TIMEOUT);
        
        if(NULL != strstr(gprsBuffer, "ERROR")){
            printf("Faile to Get IMSI\r\n");
            wait_ms(1000);
        }
        else{
          strncpy(IMSI, gprsBuffer+strlen("AT+CIMI\r\n")+1, 15);  //implement issue here
          //Serial.println(gprsBuffer);
          printf("%s\r\n", IMSI);
          str_IMSI = IMSI;
          break;
        }
    }
    
    connect_to_server();
    
    
    bool send_flag = true;
    int count = 0;
    char msg[100];
    string str_msg;
    unsigned long previousTime = 0; 
    unsigned long currentTime;
    int disconnection_count = 0;
    //string str_test = "aaaaaaaaaabbbbbbbbbbccccccccccddddddddddeeeeeeeeeeffffffffffgggggggggghhhhhhhhhhiiiiiiiiiijjjjjjjjjj"; //100bytes
    
    //pc.attach(&PC_callback);
    //nbiot_shield.attach(&NBIOT_callback);
    
    while(1) {
            
        if(nbiot_shield.readable()){ //check downlink
            pc.putc(nbiot_shield.getc());
            /*char recv_msg[50];
            if(sim7000.mqttRecv(cTopic, recv_msg, 50)){ //read buffer
                printf("recevied: %s",recv_msg);
            }*/
        }
            
        currentTime = millis();
        //printf("%d\r\n", currentTime - previousTime);
        if(currentTime - previousTime >  600000 || send_flag == true){
            send_flag = false;
            printf("---------------------------\r\n");
            sprintf(msg, "delta%d,%s", count, IMSI);
            printf("%s\r\n", msg);
            str_msg = msg;
            if (sim7000.mqttPublish(PUBLISH_TOPIC, str_msg)){
                printf("Send OK\r\n");
            }else{
                printf("Failed to send\r\n"); //Can do reconnection here
                disconnection_count++;
                sim7000.closeNetwork();
                wait_ms(1000);
                connect_to_server();
                send_flag = true;
            }
            printf("Disconnection count: %d\r\n", disconnection_count);
            previousTime = currentTime;
            count++;
        }
        //wait(1);
        
    }
    
}