ATtiny85 code for serial communication with the MG2639 cellular modem

ATtiny85_cellular_MG2639.ino

#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3); // RX, TX

// Timing Characteristics All constants in this section defined in milliseconds
#define POWER_PULSE_DURATION  2000  // 2-5s pulse required to turn on/off
#define MODULE_OFF_TIME     10000 // Time the module takes to turn off
#define COMMAND_RESPONSE_TIME 500  // Command response timeout on UART
#define MODULE_WARM_UP_TIME   3000  // Time between on and ready

const char* gprs_open = "+ZPPPOPEN:CONNECTED";
unsigned int gprs_open_len = 18;
unsigned int start_line = 0;
unsigned int end_line = 0;

unsigned int i = 0;
unsigned int j = 0;
unsigned long seconds = 0;
unsigned int loop_count = 0;
unsigned int mhz = 16000;
char serial_buff[47];
//char serial_eval[47];
//unsigned int byte_count = 0;
//char serial_out[20];

//connection
char ipSetupCmd[33] = "\0";
//emset(ipSetupCmd, "\0", 33);
const char TCP_SETUP[] = "AT+ZIPSETUP"; //at?
unsigned int channel = 0;
//IPAddress serverIP(54, 88, 179, 111);//54.88.179.111
unsigned int port = 8080;
const char getRequest1[] = "GET / HTTP/1.1";
const char getRequest2[] = "Host: 54.88.179.111:8080";
const char getRequest3[] = "message-body: {\"device_id\":\"0123456789\",\"api_key\":\"9a8b7c6d5e4f3g2h1i\"}";
const char getRequest4[] = "\n\n";


void setup() {
  
  delay(5000);
  
  // Open serial communication
  Serial.begin(9600);
  //Serial.println("Enter Serial to Start");
  //while (!Serial) {
  //  ;
  //}
  
  // initialize pins
  pinMode(7, OUTPUT);

  digitalWrite(7, HIGH);
  delay(POWER_PULSE_DURATION);
  digitalWrite(7, LOW);

  delay(MODULE_WARM_UP_TIME);
  
  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);

}

void loop() {
  
  if ( mySerial.available() > 0 ) {
    mySerial.readBytesUntil('\0', serial_buff, 47);
    //Serial.write(serial_buff);
    for ( i = 0; i < 47; i++ ) {
      
      if ( serial_buff[i] == '+' ) {
        start_line = i;
      }
      
      if ( serial_buff[i] == '\n' ) {
        end_line = i;
        for ( j = start_line; j < end_line; j++ ) {
          Serial.write(serial_buff[j]);
        }
      }
      
    }
    
  }
  
  if ( loop_count % mhz == 0 ) {
    
    seconds++;
    Serial.println(seconds);
    loop_count = 0;
    switch (seconds) {
      case 9:
        mySerial.println("AT+CIMI?");
        break;
      case 12:
        mySerial.println("A/");
        break;
      case 15:
        mySerial.println("AT+GSN");
        break;
      case 18:
        // grrp open
        mySerial.println("AT+ZPPPOPEN");
        break;
      case 23:
        sprintf(ipSetupCmd, "%s=%d,%d.%d.%d.%d,%d", TCP_SETUP, channel, 54, 88, 179, 111, port);
        mySerial.println(ipSetupCmd);
        break;
      case 25:
        mySerial.println(getRequest1);
        mySerial.println(getRequest2);
        mySerial.println(getRequest3);
        mySerial.println(getRequest4);//problem is with the println, and or the variable getRequest
        break;
      case 33:
        // turn off
        digitalWrite(7, HIGH);
        delay(POWER_PULSE_DURATION);
        digitalWrite(7, LOW);
        break;
    }
  }
  loop_count++;
  //if (Serial.available()) {
  //  mySerial.println(Serial.read());
  //}
}