Serial-SIMCOM.ino

#include <SoftwareSerial.h>

int _MODEMSTATE = 1; // set state as available
int RESET_PIN = 10 //SIM800 reset connected to pin D10
int TX_PIN = 7;
int RX_PIN = 8;
String _MESSAGEBUFFER = "";
String _SERIALBUFFER = "";

SoftwareSerial serialHologram(TX_PIN, RX_PIN);

void setup()
{
  pinMode(RESET_PIN, OUTPUT);
  digitalWrite(RESET_PIN, HIGH);
  delay(10);
  digitalWrite(RESET_PIN, LOW);
  delay(100);
  digitalWrite(RESET_PIN, HIGH);

  delay(10000); // wait for modem to startup
  
  if(!Serial) { // if user did not begin Serial then we will
      Serial.begin(19200);
      while(!Serial); // wait for Serial to be ready
  }
  
  if(!serialHologram) { // if user did not begin Serial then we will
    serialHologram.begin(19200);
    while(!serialHologram); // wait for Serial to be ready
  }
  
  Serial.println(F("Setup complete"));
}

void loop()
{
  modem_debug();
  delay(1000);
}

void read_serial() {
    // IMPORTANT: I want to tightly control reading from serialHologram,
    // this is the only function allowed to do it
    _SERIALBUFFER = "";

    if (serialHologram.available() > 0) {
        delay(20); // allow for buffer to build
        while ( serialHologram.available() > 0 ) { // move serial buffer into global String
            char r = serialHologram.read();
            _SERIALBUFFER += r;

            if (_SERIALBUFFER.endsWith("\n" )) { // we read the serial one line at a time
                _SERIALBUFFER.replace("\r","");
                _SERIALBUFFER.replace("\n","");
                // If buffer has a message then break, but if the length
                // is 0 after removing \r\n the serial needs to be read again
                if(_SERIALBUFFER.length() > 0) {
                    break;
                }
            }
        }

        Serial.print(F("DEBUG: Modem Serial Buffer = "));
        Serial.println(_SERIALBUFFER);
        if(_MESSAGEBUFFER.length() > 0) {
            Serial.print(F("DEBUG: Message Buffer = "));
            Serial.println(_MESSAGEBUFFER);
        }
    }
}

void write_serial(const char* string) {
    // Note: this expects you to check state before calling
    // IMPORTANT: I want to tightly control writing to serialHologram,
    // this is the only function allowed to do it

    Serial.print(F("DEBUG: Write Modem Serial = "));
    Serial.println(string);

    serialHologram.write(string); // send command
}

void modem_debug() {
    // keep track of anything written into the MCU serial
    // collect it and write it to the modem serial
    if (Serial.available() > 0) {
        _SERIALBUFFER = "";

        delay(100); // allow for buffer to build
        while(Serial.available() > 0) {
            char r = Serial.read();
            _SERIALBUFFER += r;
        }

        char write_string[_SERIALBUFFER.length()];
        _SERIALBUFFER.toCharArray(write_string, sizeof(write_string));
        write_serial(write_string);
    }

    // normally we get debug messages when another function runs a modem command
    // but if there is not another function using the modem then we need to listen
    // MAKE SURE Arduino serial monitor is sending both NL & CR!!
    if(_MODEMSTATE == 1 && serialHologram.available() > 0) {
        _MODEMSTATE = 0;
        while(serialHologram.available() > 0) {
            read_serial();
        }
        _MODEMSTATE = 1;
    }
}