GSM GPRS SIM900A Modem-Compatible for Arduino

Dear Sir/Madam,

GSM shield is not compatible for 3.3 V.

Dear Mr.Ram Kumar,

Since the pin outs are not compatible, the existing ardiuno library is not comatible with our GSM.

Dear Customer

Please find the code below, also the same code can be used to on/off the pump.


int8_t answer;
int x;

char SMS[200];

void setup(){

 
    Serial.begin(9600);  

    pinMode(8, OUTPUT);
            digitalWrite(8, LOW);
    power_on();
        // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second


 Serial.println("Network...");
     while( (sendATcommand("AT+CREG?", "+CREG: 0,1", 500) ||
            sendATcommand("AT+CREG?", "+CREG: 0,5", 500)) == 0 );
            
delay(300);
//Signal();
 
    
    Serial.println("Setting SMS mode...");
    sendATcommand("AT+CMGF=1", "OK", 1000);    // sets the SMS mode to text
    delay(300);
     
  sendATcommand("AT+CMGD=1", "OK", 1000);
  Serial.println("SEND SMS... TO READ");
}


void loop(){
   answer = sendATcommand("AT+CMGR=1", "+CMGR:", 2000);    // reads the first SMS
    if (answer == 1)
  {x=0;
        memset(SMS, '\0', 100);
        answer = 0;
        while(Serial.available() == 0);
        // this loop reads the data of the SMS
        do{
            // if there are data in the UART input buffer, reads it and checks for the asnwer
            if(Serial.available() > 0){
           
          
                SMS[x] = Serial.read();
                x++;
                // check if the desired answer (OK) is in the response of the module
             
                
                 if (strstr(SMS, "PUMP ON") != NULL)    
                {
                  digitalWrite(8, HIGH);
                     answer = 1;
                }
                
                  if (strstr(SMS, "PUMP OFF") != NULL)    
                {
                   digitalWrite(8, LOW);
                      answer = 1;
                }
                   if (strstr(SMS, "OK") != NULL)    
                {
                    answer = 1;
                }
                
            }
        }while(answer == 0);    // Waits for the asnwer with time out
        
        
        SMS[x] = '\0';
               Serial.print(SMS);   
          delay(200);
        sendATcommand("AT+CMGD=1", "OK", 1000);   
                 delay(100);
                 sendATcommand("AT+CMGD=1,4", "OK", 1000);
                       delay(200);
                

    }
   
    delay(1000);
 
}

void power_on(){

    uint8_t answer=0;
    
    // checks if the module is started
    answer = sendATcommand("AT", "OK", 2000);
    if (answer == 0)
    {
        
    
        // waits for an answer from the module
        while(answer == 0){     // Send AT every two seconds and wait for the answer
            answer = sendATcommand("AT", "OK", 2000);    
        }
    }
    
}

int8_t sendATcommand(char* ATcommand, char* expected_answer, unsigned int timeout){

    uint8_t x=0,  answer=0;
    char response[100];
    unsigned long previous;

    memset(response, '\0', 100);    // Initialice the string

    delay(100);

    while( Serial.available() > 0) Serial.read();    // Clean the input buffer

    Serial.println(ATcommand);    // Send the AT command


        x = 0;
    previous = millis();

    // this loop waits for the answer
    do{
        // if there are data in the UART input buffer, reads it and checks for the asnwer
        if(Serial.available() != 0){    
            response[x] = Serial.read();
            x++;
            // check if the desired answer is in the response of the module
            if (strstr(response, expected_answer) != NULL)    
            {
                answer = 1;
            }
        }
        // Waits for the asnwer with time out
    }while((answer == 0) && ((millis() - previous) < timeout));    

    return answer;
}


void Signal()
{
answer = sendATcommand("AT+CSQ", "+CSQ", 2000);    // reads the first SMS
     
    if (answer == 1)
    {x=0;
        memset(SMS, '\0', 300);
        answer = 0;
        while(Serial.available() == 0);
        // this loop reads the data of the SMS
        do{
            // if there are data in the UART input buffer, reads it and checks for the asnwer
            if(Serial.available() > 0){    
                SMS[x] = Serial.read();
                x++;
       
                if (strstr(SMS, "OK") != NULL)    
                {
                    answer = 1;
                }
            }
        }while(answer == 0);    // Waits for the asnwer with time out
        
        
        SMS[x] = '\0';
         Serial.println(SMS);
         
               delay(100);
    }
    
}

Dear Sir,

Warm Greetings

Please find the ardiuno SMS Send/ Recieve code mentioned below, please try with it.load the below mentioned code to the ardiuno and mount the GSM, and provide 12v/2a supply.

Receive SMS :

int8_t answer;
int x;

char SMS[200];

void setup(){

 
    Serial.begin(9600);  

   
    power_on();
    
delay(3000);
 Serial.println("Network...");
     while( (sendATcommand("AT+CREG?", "+CREG: 0,1", 500) ||
            sendATcommand("AT+CREG?", "+CREG: 0,5", 500)) == 0 );
            
delay(300);
Signal();
    delay(3000);
    
    Serial.println("Setting SMS mode...");
    sendATcommand("AT+CMGF=1", "OK", 1000);    // sets the SMS mode to text
    
     
  sendATcommand("AT+CMGD=1", "OK", 1000);
  Serial.println("SEND SMS... TO READ");
}


void loop(){
   answer = sendATcommand("AT+CMGR=1", "+CMGR:", 2000);    // reads the first SMS
    if (answer == 1)
    {
        answer = 0;
        while(Serial.available() == 0);
        // this loop reads the data of the SMS
        do{
            // if there are data in the UART input buffer, reads it and checks for the asnwer
            if(Serial.available() > 0){    
                SMS[x] = Serial.read();
                x++;
                // check if the desired answer (OK) is in the response of the module
                if (strstr(SMS, "OK") != NULL)    
                {
                    answer = 1;
                }
            }
        }while(answer == 0);    // Waits for the asnwer with time out
        
        SMS[x] = '\0';
        
        Serial.print(SMS);    
        
    }
    delay(1000);
 
}

void power_on(){

    uint8_t answer=0;
    
    // checks if the module is started
    answer = sendATcommand("AT", "OK", 2000);
    if (answer == 0)
    {
        
    
        // waits for an answer from the module
        while(answer == 0){     // Send AT every two seconds and wait for the answer
            answer = sendATcommand("AT", "OK", 2000);    
        }
    }
    
}

int8_t sendATcommand(char* ATcommand, char* expected_answer, unsigned int timeout){

    uint8_t x=0,  answer=0;
    char response[100];
    unsigned long previous;

    memset(response, '\0', 100);    // Initialice the string

    delay(100);

    while( Serial.available() > 0) Serial.read();    // Clean the input buffer

    Serial.println(ATcommand);    // Send the AT command


        x = 0;
    previous = millis();

    // this loop waits for the answer
    do{
        // if there are data in the UART input buffer, reads it and checks for the asnwer
        if(Serial.available() != 0){    
            response[x] = Serial.read();
            x++;
            // check if the desired answer is in the response of the module
            if (strstr(response, expected_answer) != NULL)    
            {
                answer = 1;
            }
        }
        // Waits for the asnwer with time out
    }while((answer == 0) && ((millis() - previous) < timeout));    

    return answer;
}


void Signal()
{
answer = sendATcommand("AT+CSQ", "+CSQ", 2000);    // reads the first SMS
     
    if (answer == 1)
    {x=0;
        memset(SMS, '\0', 300);
        answer = 0;
        while(Serial.available() == 0);
        // this loop reads the data of the SMS
        do{
            // if there are data in the UART input buffer, reads it and checks for the asnwer
            if(Serial.available() > 0){    
                SMS[x] = Serial.read();
                x++;
       
                if (strstr(SMS, "OK") != NULL)    
                {
                    answer = 1;
                }
            }
        }while(answer == 0);    // Waits for the asnwer with time out
        
        SMS[x] = '\0';
         Serial.println(SMS);
    }
    
}
---------------------------------------------------------------------------------------------------------------------------------

SMS Send :

int8_t answer;
int onModulePin= 9;
char aux_string[30];
char phone_number[]="1234567890";

void setup(){

    pinMode(onModulePin, OUTPUT);
    Serial.begin(9600);    
        
 
    power_on();
    
    
    

    delay(3000);
    
    Serial.println("Connecting to the network...");

    while( (sendATcommand("AT+CREG?", "+CREG: 0,1", 500) ||
            sendATcommand("AT+CREG?", "+CREG: 0,5", 500)) == 0 );

    Serial.print("Setting SMS mode...");
    sendATcommand("AT+CMGF=1", "OK", 1000);    // sets the SMS mode to text
    Serial.println("Sending SMS");
    
    sprintf(aux_string,"AT+CMGS=\"%s\"", phone_number);
    answer = sendATcommand(aux_string, ">", 2000);    // send the SMS number
    if (answer == 1)
    {
        Serial.println("Test-GSM-Hello World");
        Serial.write(0x1A);
        answer = sendATcommand("", "OK", 20000);
        if (answer == 1)
        {
            Serial.print("Sent ");    
        }
        else
        {
            Serial.print("error ");
        }
    }
    else
    {
        Serial.print("error ");
        Serial.println(answer, DEC);
    }

}


void loop(){

}

void power_on(){

    uint8_t answer=0;
    
    // checks if the module is started
    answer = sendATcommand("AT", "OK", 2000);
    if (answer == 0)
    {
        // power on pulse
        digitalWrite(onModulePin,HIGH);
        delay(3000);
        digitalWrite(onModulePin,LOW);
    
        // waits for an answer from the module
        while(answer == 0){     // Send AT every two seconds and wait for the answer
            answer = sendATcommand("AT", "OK", 2000);    
        }
    }
    
}

int8_t sendATcommand(char* ATcommand, char* expected_answer, unsigned int timeout){

    uint8_t x=0,  answer=0;
    char response[100];
    unsigned long previous;

    memset(response, '\0', 100);    // Initialice the string
    
    delay(100);
    
    while( Serial.available() > 0) Serial.read();    // Clean the input buffer
    
    Serial.println(ATcommand);    // Send the AT command


    x = 0;
    previous = millis();

    // this loop waits for the answer
    do{
        // if there are data in the UART input buffer, reads it and checks for the asnwer
        if(Serial.available() != 0){    
            response[x] = Serial.read();
            x++;
            // check if the desired answer is in the response of the module
            if (strstr(response, expected_answer) != NULL)    
            {
                answer = 1;
            }
        }
    // Waits for the asnwer with time out
    }while((answer == 0) && ((millis() - previous) < timeout));    

    return answer;
}

Dear Sir

HTTPS is not supported by sim900a modems. It supports FTP/HTTP.

Dear Vikranth,

Please find the code below,

int8_t answer;
int x;
int onModulePin= 9;
char SMS[200];

void setup(){

pinMode(onModulePin, OUTPUT);
Serial.begin(9600);

power_on();

delay(3000);

Serial.println("Setting SMS mode...");
sendATcommand("AT+CMGF=1", "OK", 1000); // sets the SMS mode to text

answer = sendATcommand("AT+CMGR=1", "+CMGR:", 2000); // reads the first SMS
if (answer == 1)
{
answer = 0;
while(Serial.available() == 0);
// this loop reads the data of the SMS
do{
// if there are data in the UART input buffer, reads it and checks for the asnwer
if(Serial.available() > 0){
SMS[x] = Serial.read();
x++;
// check if the desired answer (OK) is in the response of the module
if (strstr(SMS, "OK") != NULL)
{
answer = 1;
}
}
}while(answer == 0); // Waits for the asnwer with time out

SMS[x] = '\0';

Serial.print(SMS);

}
else
{
Serial.print("error ");
Serial.println(answer, DEC);
}

}

void loop(){

}

void power_on(){

uint8_t answer=0;

// checks if the module is started
answer = sendATcommand("AT", "OK", 2000);
if (answer == 0)
{
// power on pulse
digitalWrite(onModulePin,HIGH);
delay(3000);
digitalWrite(onModulePin,LOW);

// waits for an answer from the module
while(answer == 0){ // Send AT every two seconds and wait for the answer
answer = sendATcommand("AT", "OK", 2000);
}
}

}

int8_t sendATcommand(char* ATcommand, char* expected_answer, unsigned int timeout){

uint8_t x=0, answer=0;
char response[100];
unsigned long previous;

memset(response, '\0', 100); // Initialice the string

delay(100);

while( Serial.available() > 0) Serial.read(); // Clean the input buffer

Serial.println(ATcommand); // Send the AT command

x = 0;
previous = millis();

// this loop waits for the answer
do{
// if there are data in the UART input buffer, reads it and checks for the asnwer
if(Serial.available() != 0){
response[x] = Serial.read();
x++;
// check if the desired answer is in the response of the module
if (strstr(response, expected_answer) != NULL)
{
answer = 1;
}
}
// Waits for the asnwer with time out
}while((answer == 0) && ((millis() - previous) < timeout));

return answer;
}

Dear Sir

Kindly go through the below links and the difference between the modems,

1. http://researchdesignlab.com/gsm-gprs-sim900a-modem-compatible-for-arduino.html

RDL/RGS/14/001/V1.0 -> This is a simple arduino shield which gets mounted on top or any arduino uno or arduino uno clone boards. Needs an adapter of 12V,2A to turn on this modem plugged into arduino uno DC socket. Other arduino shields could be mounted on top of this. No audio/mic jack are present on board.

2.http://researchdesignlab.com/gsm-modem-arduino-compatible.html

RDL/GSM-A/14/14/001/V3.0 -> This is a simple arduino shield which gets mounted on top or any arduino uno or arduino uno clone boards. Needs an adapter of 12V,2A to turn on this modem plugged into arduino uno DC socket. Other arduino shields can not mounted on top of this. Audio/mic jack are present on board.

3. http://researchdesignlab.com/gsm-gprs-shield.html

RDL/GSM-GPRS/14/001/V3.0 , -> is an industrial standard grade product with current controlling IC on board. This is also an arduino shield which gets mounted on top or any arduino uno or arduino uno clone boards. No need of external power supply for the arduino board.(USB power is enough). This has got inbuilt DC to DC converter.