SIM800L Library use in our Industrial Arduino GPRS PLC

This post shows how to use the Sim800L GPRS Module Library >>

This library is developed by Adafruit and communicates with the GSM modules through Serial TTL.

In the case of Ardbox PLCs, you need to use the library SoftwareSerial.h >>

GPRS Module basic description

Industrial controller based on Arduino technology designed for professional use. This programmable logic controller has 17 I/Os. It also contains several communication ports which provide more flexibility and control. 

The GPRS/GSM Controller Arduino offers the possibility to expand up to 127 modules through I2C. This model also includes GPRS Hardware for GPRS communication. SIM card is not included!

GRPS M-Duino Arduino PLC >> 

Sim800L general specifications (GPRS Integrated module)

§  Quad-Band GSM 850/900/1800 / 1900MHz

§  GPRS multi-slot class 12/10

§  GPRS mobile station class B

§  GSM 2/2 +FM frequency between 76 MHz and 109 kHz adjustable by step 50AT command set support (3GPP TS 27.007, 27.005 and augmented by SIMCOM AT)

§  Class 4 (2W at 850 / 900MHz)

§  Class 1 (1 W at 1800 / 1900MHz)

§  Serial interface

§  SIM card interface 3 V / 1.8 V

Example of a SIM800L Arduino Library

This code will receive an SMS, identify the sender's phone number, and automatically send a response.

The internal connections between the internal Arduino Mega of the GPRS Module and the Sim800L are shown below:

REMEMBER: Open up the serial console on the Arduino at 115200 baudrate!

/***************************************************
  This is an example for our Adafruit FONA Cellular Module
  Designed specifically to work with the Adafruit FONA
  ----> http://www.adafruit.com/products/1946
  ----> http://www.adafruit.com/products/1963
  ----> http://www.adafruit.com/products/2468
  ----> http://www.adafruit.com/products/2542
  These cellular modules use TTL Serial to communicate, 2 pins are
  required to interface
  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing
  products from Adafruit!
  Written by Limor Fried/Ladyada for Adafruit Industries.
  BSD license, all text above must be included in any redistribution
 ****************************************************/

/*
THIS CODE IS STILL IN PROGRESS!
Open up the serial console on the Arduino at 115200 baud to interact with FONA
 */

#include "Adafruit_FONA.h"

#define FONA_RX 19 //RX1 on Arduino Mega
#define FONA_TX 18 //TX1 on Arduino Mega
#define FONA_RST 2

// this is a large buffer for replies
char replybuffer[255];

// We default to using software serial. If you want to use hardware serial
// (because softserial isnt supported) comment out the following three lines 
// and uncomment the HardwareSerial line
#include <SoftwareSerial.h>
SoftwareSerial fonaSS = SoftwareSerial(FONA_TX, FONA_RX);
SoftwareSerial *fonaSerial = &fonaSS;

// Hardware serial is also possible!
//  HardwareSerial *fonaSerial = &Serial1;

// Use this for FONA 800 and 808s
Adafruit_FONA fona = Adafruit_FONA(FONA_RST);
// Use this one for FONA 3G
//Adafruit_FONA_3G fona = Adafruit_FONA_3G(FONA_RST);

uint8_t readline(char *buff, uint8_t maxbuff, uint16_t timeout = 0);

void setup() {
  while (!Serial);

  Serial.begin(115200);
  Serial.println(F("FONA SMS caller ID test"));
  Serial.println(F("Initializing....(May take 3 seconds)"));

  // make it slow so its easy to read!
  fonaSerial->begin(4800);
  if (! fona.begin(*fonaSerial)) {
    Serial.println(F("Couldn't find FONA"));
    while(1);
  }
  Serial.println(F("FONA is OK"));

  // Print SIM card IMEI number.
  char imei[16] = {0}; // MUST use a 16 character buffer for IMEI!
  uint8_t imeiLen = fona.getIMEI(imei);
  if (imeiLen > 0) {
    Serial.print("SIM card IMEI: "); Serial.println(imei);
  }

  fonaSerial->print("AT+CNMI=2,1\r\n");  //set up the FONA to send a +CMTI notification when an SMS is received

  Serial.println("FONA Ready");
}

  
char fonaNotificationBuffer[64];          //for notifications from the FONA
char smsBuffer[250];

void loop() {
  
  char* bufPtr = fonaNotificationBuffer;    //handy buffer pointer
  
  if (fona.available())      //any data available from the FONA?
  {
    int slot = 0;            //this will be the slot number of the SMS
    int charCount = 0;
    //Read the notification into fonaInBuffer
    do  {
      *bufPtr = fona.read();
      Serial.write(*bufPtr);
      delay(1);
    } while ((*bufPtr++ != '\n') && (fona.available()) && (++charCount < (sizeof(fonaNotificationBuffer)-1)));
    
    //Add a terminal NULL to the notification string
    *bufPtr = 0;

    //Scan the notification string for an SMS received notification.
    //  If it's an SMS message, we'll get the slot number in 'slot'
    if (1 == sscanf(fonaNotificationBuffer, "+CMTI: " FONA_PREF_SMS_STORAGE ",%d", &slot)) {
      Serial.print("slot: "); Serial.println(slot);
      
      char callerIDbuffer[32];  //we'll store the SMS sender number in here
      
      // Retrieve SMS sender address/phone number.
      if (! fona.getSMSSender(slot, callerIDbuffer, 31)) {
        Serial.println("Didn't find SMS message in slot!");
      }
      Serial.print(F("FROM: ")); Serial.println(callerIDbuffer);

        // Retrieve SMS value.
        uint16_t smslen;
        if (fona.readSMS(slot, smsBuffer, 250, &smslen)) { // pass in buffer and max len!
          Serial.println(smsBuffer);
        }

      //Send back an automatic response
      Serial.println("Sending reponse...");
      if (!fona.sendSMS(callerIDbuffer, "Hey, I got your text!")) {
        Serial.println(F("Failed"));
      } else {
        Serial.println(F("Sent!"));
      }
      
      // delete the original msg after it is processed
      //   otherwise, we will fill up all the slots
      //   and then we won't be able to receive SMS anymore
      if (fona.deleteSMS(slot)) {
        Serial.println(F("OK!"));
      } else {
        Serial.print(F("Couldn't delete SMS in slot ")); Serial.println(slot);
        fona.print(F("AT+CMGD=?\r\n"));
      }
    }
  }
}