Arduino, GSM shield, AT+CMGR and +CMGL don't respond with SMS text data

Question

I am new to Arduino and GSM shield. I have been working with SMS, and I have a problem to read the SMS's text contents from the modem.

Here is the setting for the Arduino and the GSM.

#include <SoftwareSerial.h>
SoftwareSerial sim900(7, 8);

#define BUFF_SIZE 400

char buffer[BUFF_SIZE];
bool GSMconnected = false;

//functions
bool copyResponse(int* size);
void printBuff(int size);
bool readlnbuffer(int* start, int* nextline, int* size);
bool isResponseOK(int start, int endofline);
bool checkConnection();
bool checkMessage(int index);
bool checkString(int start, int end, String command);
bool checkSMS(int start, int nextline);
bool newMessage();

void setup() {
  sim900.begin(9600);
  Serial.begin(9600);
  delay(100);
  pinMode(relayIN, OUTPUT);
  delay(100);
  while (!GSMconnected) {
    checkConnection();
    delay(10000);
  }
  int rsize;
  //text mode
  sim900.print("AT+CMGF=1\r");
  delay(1000);

  //store message in SIM card
  sim900.print("AT+CPMS=\"SM\"\r");
  delay(1000);

  sim900.print("AT+CMGD=0,4\r\n");
  delay(1000);
  copyResponse(&rsize);
  printBuff(rsize);
  /*
     0: do not show header values
     1: show the values in result codes
  */
  sim900.print("AT+CSDH=1\r");
  delay(1000);
  //receive mode +CMTI:"SM", 1
  sim900.print("AT+CNMI=2,2,0,0,0 \r");
  delay(1000);
  copyResponse(&rsize);
  printBuff(rsize);

  sim900.print("AT+CSMP=17,167,0,0\r\n");
  delay(10000);
  copyResponse(&rsize);
  printBuff(rsize);
  Serial.println("GSM is ready");

I want to check the SMS message when there is a new SMS. So I simply call the function when the GSM is available.

void loop() {
  if(sim900.available()) {
    newMessage();
  }
}

newMessage() checks the index of the new SMS stored in the SIM card.

bool newMessage() {
  int responseSize;
  if (!copyResponse(&responseSize)) {
    return false;
  }
  //+CMTI: “SM”,1
  //read a line and check if there is a SMS
  int start = 0;
  int nextline = 0;
  int index;
  while (readlnbuffer(&start, &nextline, &responseSize)) {
    String command = "+CMTI: \"SM\",";
    if (checkString(start, start + 12, command)) {
      Serial.println("SMS found");
      index = int(buffer[start + 12]);
      break;
    }
    start = nextline;
  }

  //debug
  printBuff(responseSize);
  delay(10000);
  if (checkMessage(index)) {
    //delete message
    sim900.print("AT+CMGD=");
    sim900.print(char(index));
    sim900.println("\r");
    delay(100);
    return true;
  } else {
    return false;
  }

checkMessage() reads SMS message and should print SMS text data.

bool checkMessage(int index) {
  //listing
  //sim900.print("AT+CMGL=\"REC UNREAD\"\r\n");
  //reading
  sim900.print("AT+CMGR=");
  sim900.print(char(index));
  sim900.print("\r\n");
  delay(5000);
  int responseSize;
  if (!copyResponse(&responseSize)) {
    return false;
  }
  delay(100);

  //debug, to check what is in the buffer
  printBuff(responseSize);
  //read a line and check if there is a SMS
  int start = 0;
  int nextline = 0;
  bool isSMS = false;
  while (!isSMS) {
    start = nextline;
    if (!readlnbuffer(&start, &nextline, &responseSize)) {
      Serial.println("no SMS found");
      return false;
    }
    String command = "+CMGR:";
    if (checkString(nextline, nextline + 6, command)) {
      Serial.println("SMS checking");
      isSMS = true;
    }
  }

  //debug
  if (!readlnbuffer(&start, &nextline, &responseSize)) {
    Serial.println("cannot read the sms info");
    return false;
  }
  Serial.println("SMS message: ");
  for (int i = start; i < nextline; i++) {
    //debug
    Serial.print(buffer[i]);
  }
  Serial.println("");
}

When I run the code, it looks like the response for AT+CMGR cannot be copied completely. Here is what the Serial monitor shows.

checking the network

AT+CREG?

+CREG: 0,1

OK

AT+CMGF=1

OK

AT+CPMS="SM"

+CPMS: 1,30,1,30,1,30

OK

AT+

AT+CSDH=1

OK

AT+CNMI=2,1,0,0,0

OK

AT+CSMP=17,167,0,0

OK

GSM is ready

SMS found

+CMTI: "SM",1

AT+CMGR=1

> +CMGR: "REC UNREAD","+123456789","","17/11/26,11

SMS checking

SMS message:

AT+CMGD=1

OK

I think I went wrong with copying the response in the buffer. I am also a beginner of writing code and I need some help. Can anyone advise me on why I am getting this problem?

Thank you!

hlovdal hlovdal · Accepted Answer · 2017-11-27T20:00:42

I think the problem is that you are aborting the command by using delay which you should never, never, ever do as a substitute for reading and parsing the responses from the mopdem.

For hints on removing delay usage see the linked answer (and for details on aborting command you can see V.250).

Arduino, GSM shield, AT+CMGR and +CMGL don't respond with SMS text data

1 Answers