December 15, 2015 by Dost Muhammad Shah on Electronics

GET request using AT commands SIM800 SIM900

In this post I am writing how to send a GET request using GSM Module with AT commands. It should work with any module and has been tested to work with Sim800 series (SIM800C-DS , SIM800A, SIM800H, SIM800L, SIM800C, SIM800 etc) and Sim900 series (SIM900, SIM900A, SIM900D, SIM900B) of modules from simcom.

February 20, 2015 by Dost Muhammad Shah on Coding, Electronics, Microcontrollers

upload/downlaod file from FTP using AT commands (Sim900 + arduino)

In the previous post I explained how to make a connection and send data via TCP connection on SIM900 and similar modems. This post is going to be about FTP connection. FTP stands for “file transfer protocol.” FTP powers one of the fundamental Internet functions and is the prescribed method for the transfer of files between computers. It is also the easiest and most secure way to exchange files over the Internet.

Without going into much details I would show the related AT commands and brief description. Later I would include sample code for FTP upload/download using arduino and SIM900

AT command	Response	Description
AT+SAPBR	OK	Configures GPRS profile.
AT+FTPCID=1	OK	Selects profile 1 for FTP.
AT+FTPSERV=”****”	OK	Sets FTP server domain name or IP address. **** is the domain name or the IP.
AT+FTPPORT=***	OK	Sets FTP server port. *** is the port.
AT+FTPUN=”***”	OK	Sets user name for FTP server access. *** is the user name.
AT+FTPPW=”***”	OK	Sets password for FTP server access. *** is the password.
AT+FTPPUTNAME=”****”	OK	Sets destiny name for the file.*** is the name of the file.
AT+FTPPUTPATH=”****”	OK	Sets destiny file path. *** is the path of the file.
AT+FTPPUT	OK	Use to put a file into the FTP server.
AT+FTPGETNAME=”****”	OK	Sets origin name for the file.*** is the name of the file.
AT+FTPGETPATH=”****”	OK	Sets origin file path. *** is the path of the file.
AT+FTPGET		Use to get a file into the FTP server.

Make sure you have a server and note the ftp port, we would consider using the default port 21. Switch on your modem and make sure pin code is disabled or properly entered and that GPRS connection is available.

Configure GPRS by sending AT+SAPBR=3,1,”Contype”,”GPRS”r .
Set APN by sending AT+SAPBR=3,1,”APN”,”your apn”r .replace your apn with APN for your network.
Now set the username and password for the apn (replace username and password with correct values )
AT+SAPBR=3,1,”USER”,”username”r .
AT+SAPBR=3,1,”PASS”,”password”r
Connect to GPRS connection by sending AT+SAPBR=1,1r, when connected Modem will respond with OK
Now select profile 1 for FTP by sending AT+FTPCID=1r
Now set FTP server domain or ip using the command AT+FTPSERV=ftp.yourserver.comr
Set FTP port by AT+FTPPORT=21r
Now send FTP credentials using AT+FTPUN=user_namer and AT+FTPPW=”password”r
To get a file from FTP send AT+FTPGETNAME=file_namer
Now set the path of the file AT+FTPGETPATH=/path/r
Now send AT+FTPGET=1r and wait for response from server, which starts with +FTPGET:1,1
To upload a file to FTP server send AT+FTPPUTNAME=file_namer
Now set path AT+FTPPUTPATH=/pathr
Now send AT+FTPPUT=1 and wait for +FTPPUT:1,1 after which you need to send the content of file to be uploaded.

int8_t answer;
int onModulePin = 2;
char aux_str[30];

char incoming_data[120];

char test_str[ ]= "0000000011111111222222223333333344444444555555556666666677777777000000001111111122222222333333334444";

int data_size, aux;


void setup(){

    pinMode(onModulePin, OUTPUT);
    Serial.begin(115200);


    Serial.println("Starting...");
    power_on();

    delay(5000);

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

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

    configure_FTP();

    uploadFTP();

    downloadFTP();

    Serial.print("Incoming data: ");
    Serial.println(incoming_data);
}


void loop(){

}


void configure_FTP(){

    sendATcommand("AT+SAPBR=3,1,"Contype","GPRS"", "OK", 2000);
    sendATcommand("AT+SAPBR=3,1,"APN","APN"", "OK", 2000);
    sendATcommand("AT+SAPBR=3,1,"USER","user_name"", "OK", 2000);
    sendATcommand("AT+SAPBR=3,1,"PWD","password"", "OK", 2000);

    while (sendATcommand("AT+SAPBR=1,1", "OK", 20000) != 1);
    sendATcommand("AT+FTPCID=1", "OK", 2000);
    sendATcommand("AT+FTPSERV="ftp.yourserver.com"", "OK", 2000);
    sendATcommand("AT+FTPPORT=21", "OK", 2000);
    sendATcommand("AT+FTPUN="user_name"", "OK", 2000);
    sendATcommand("AT+FTPPW="password"", "OK", 2000);

}


void uploadFTP(){

    sendATcommand("AT+FTPPUTNAME="file_name"", "OK", 2000);
    sendATcommand("AT+FTPPUTPATH="/path"", "OK", 2000);
    if (sendATcommand("AT+FTPPUT=1", "+FTPPUT:1,1,", 30000) == 1)
    {
        data_size = 0;
        while(Serial.available()==0);
        aux = Serial.read();
        do{
            data_size *= 10;
            data_size += (aux-0x30);
            while(Serial.available()==0);
            aux = Serial.read();
        }
        while(aux != 0x0D);

        if (data_size >= 100)
        {
            if (sendATcommand("AT+FTPPUT=2,100", "+FTPPUT:2,100", 30000) == 1)
            {
                Serial.println(sendATcommand(test_str, "+FTPPUT:1,1", 30000), DEC);
                Serial.println(sendATcommand("AT+FTPPUT=2,0", "+FTPPUT:1,0", 30000), DEC);
                Serial.println("Upload done!!");
            }
            else
            {
                sendATcommand("AT+FTPPUT=2,0", "OK", 30000);
            }
        }
        else
        {
            sendATcommand("AT+FTPPUT=2,0", "OK", 30000);
        }
    }
    else
    {
        Serial.println("Error openning the FTP session");
    }
}

void downloadFTP(){

    int x = 0;

    sendATcommand("AT+FTPGETNAME="file_name"", "OK", 2000);
    sendATcommand("AT+FTPGETPATH="/path"", "OK", 2000);
    if (sendATcommand("AT+FTPGET=1 ", "+FTPGET:1,1", 30000) == 1)
    {
        do{
            if (sendATcommand2("AT+FTPGET=2,50", "+FTPGET:2,", "+FTPGET:1,", 30000) == 1)
            {
                data_size = 0;
                while(Serial.available()==0);
                aux = Serial.read();
                do{
                    data_size *= 10;
                    data_size += (aux-0x30);
                    while(Serial.available()==0);
                    aux = Serial.read();
                }while(aux != 0x0D);

                Serial.print("Data received: ");
                Serial.println(data_size);

                if (data_size > 0)
                {
                    while(Serial.available() < data_size);
                    Serial.read();

                    for (int y = 0; y < data_size; y++)
                    {
                        incoming_data[x] = Serial.read();
                        x++;
                    }
                    incoming_data[x] = '';
                }
                else
                {
                    Serial.println("Download finished");
                }
            }
            else if (answer == 2)
            {
                Serial.println("Error from FTP");
            }
            else
            {
                Serial.println("Error getting the file");
                data_size = 0;
            }
        }while (data_size > 0);
    }
    else
    {
        Serial.println("Error openning the FTP session");
    }
}




void power_on(){

    uint8_t answer=0;

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

        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, '', 100);    // Initialize 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(Serial.available() != 0){
            // if there are data in the UART input buffer, reads it and checks for the asnwer
            response[x] = Serial.read();
            //Serial.print(response[x]);
            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;
}

int8_t sendATcommand2(char* ATcommand, char* expected_answer1,
            char* expected_answer2, unsigned int timeout){

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

    memset(response, '', 100);    // Initialize 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 1 is in the response of the module
            if (strstr(response, expected_answer1) != NULL)
            {
                answer = 1;
            }
            // check if the desired answer 2 is in the response of the module
            if (strstr(response, expected_answer2) != NULL)
            {
                answer = 2;
            }
        }
        // Waits for the asnwer with time out
    }while((answer == 0) && ((millis() - previous) < timeout));

        return answer;
}

February 14, 2015 by Dost Muhammad Shah on Coding, Electronics

TCP connection over GPRS using SIM900 and similar modems using AT commands

GSM/GPRS modems are getting very common these days, as prices are getting cheaper and cheaper. Apart from providing SMS and call functions to my projects I also wanted to communicate via TCP.

Although there are many documents and blog posts to help but I have always found that they either are answers to specific problem faced by someone or not providing complete details. In this post I would first explain the AT commands used in brief. You may connect your SIM900 to your computer via a serial/usb and test these commands. In the later part of this post I would include arduino example code.

AT commands for TCP/UDP Connection with example response and a brief description are given in the table below. Refer to the AT commands manual of your modem for details

AT command	Response	Description
AT	OK	test command. reply is OK
AT+CGATT?	+CGATT:n	checks if GPRS is attached? n=1 if attached
AT+CIPMUX=n	OK	use n as 0 for single connection or use 1 for multiple connections
AT+CSTT=”apn”,”username”,”pass”	OK	Sets APN, user name and password
AT+CIICR	OK	Brings up wireless connection
AT+CIFSR	ip address	Get local IP address if connected
AT+CIPSTART=“TYPE” , “domain”, “port”	Connected	Establishes a connection with a server. Type can be UDP or TCP
AT+CIPSEND	>	Sends data when the a connection is established.
AT+CIPCLOSE	OK	Closes the connection
AT+CIPSHUT	SHUT OK	resets IP session if any

how to make a connection:

Send ATr and wait for a response from the modem. You should recieve OK
if everything is set.
Make sure that the Modem has registered to network and that PIN code is disabled on the SIM. Send AT+CGATT?r to check if GPRS is attached or not. +CGATT: 1 indicates that GPRS is attached.
Send AT+CIPSHUTr . Although its optional this will be helpful as it resets IP session if any. you will get a response SHUT OK .
Send AT+CIPMUX=0 to set a single connection mode, response would be OK
Now set APN settings by AT+CSTT= “apn ”, “username”, “password”r . replace apn, username and password to match APN (Access Point Name) ,username and password for your service provider.
Now send AT+CIICRr , this will bring up the wireless connection. OK is received on successful connection
Send AT+CIFSRr , this will reply with the IP address the modem has been assigned.
Send AT+CIPSTART=”TCP”,”server domain name or ip”,”port”r, replace the domain name/ip and port with appropriate values, on connection modem will reply with CONNECT OK
Now you can send your data using AT+CIPSENDr AT command. modem will respond with > indicating it is ready to receive data to be sent. Type in your data.
Now the modem is waiting for the ASCII 26 that is control+z on keyboard. Depending on the terminal software used you can either press control and Z together on keyboard or send hex value 0x1A. The modem will then send the response from server.
Now send AT+CIPSHUT to shut down the connection. Modem will reply with SHUT OK
cheers 🙂

ARDUINO CODE :

Below is example code for single and multiple connection using arduino and sim900

int8_t answer;
int onModulePin= 2;
char aux_str[50];
char ip_data[40]="Test string from GPRS shieldrn";
void setup(){
    pinMode(onModulePin, OUTPUT);
    Serial.begin(115200);
    Serial.println("Starting...");
    power_on();
    delay(3000);
    // sets the PIN code
    sendATcommand2("AT+CPIN=****", "OK", "ERROR", 2000);
    delay(3000);
    Serial.println("Connecting to the network...");
    while( sendATcommand2("AT+CREG?", "+CREG: 0,1", "+CREG: 0,5", 1000)== 0 );
}
void loop(){
    // Selects Single-connection mode
    if (sendATcommand2("AT+CIPMUX=0", "OK", "ERROR", 1000) == 1)
    {
        // Waits for status IP INITIAL
        while(sendATcommand2("AT+CIPSTATUS", "INITIAL", "", 500)  == 0 );
        delay(5000);

        // Sets the APN, user name and password
        if (sendATcommand2("AT+CSTT="APN","user_name","password"", "OK",  "ERROR", 30000) == 1)
        {
            // Waits for status IP START
            while(sendATcommand2("AT+CIPSTATUS", "START", "", 500)  == 0 );
            delay(5000);

            // Brings Up Wireless Connection
            if (sendATcommand2("AT+CIICR", "OK", "ERROR", 30000) == 1)
            {
                // Waits for status IP GPRSACT
                while(sendATcommand2("AT+CIPSTATUS", "GPRSACT", "", 500)  == 0 );
                delay(5000);

                // Gets Local IP Address
                if (sendATcommand2("AT+CIFSR", ".", "ERROR", 10000) == 1)
                {
                    // Waits for status IP STATUS
                    while(sendATcommand2("AT+CIPSTATUS", "IP STATUS", "", 500)  == 0 );
                    delay(5000);
                    Serial.println("Openning TCP");

                    // Opens a TCP socket
                    if (sendATcommand2("AT+CIPSTART="TCP","IP_address","port"",
                            "CONNECT OK", "CONNECT FAIL", 30000) == 1)
                    {
                        Serial.println("Connected");

                        // Sends some data to the TCP socket
                        sprintf(aux_str,"AT+CIPSEND=%d", strlen(ip_data));
                        if (sendATcommand2(aux_str, ">", "ERROR", 10000) == 1)
                        {
                            sendATcommand2(ip_data, "SEND OK", "ERROR", 10000);
                        }

                        // Closes the socket
                        sendATcommand2("AT+CIPCLOSE", "CLOSE OK", "ERROR", 10000);
                    }
                    else
                    {
                        Serial.println("Error openning the connection");
                    }
                }
                else
                {
                    Serial.println("Error getting the IP address");
                }
            }
            else
            {
                Serial.println("Error bring up wireless connection");
            }
        }
        else
        {
            Serial.println("Error setting the APN");
        }
    }
    else
    {
        Serial.println("Error setting the single connection");
    }

    sendATcommand2("AT+CIPSHUT", "OK", "ERROR", 10000);
    delay(10000);
}

void power_on(){

    uint8_t answer=0;

    // checks if the module is started
    answer = sendATcommand2("AT", "OK", "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 = sendATcommand2("AT", "OK", "OK", 2000);
        }
    }

}

int8_t sendATcommand2(char* ATcommand, char* expected_answer1,
        char* expected_answer2, unsigned int timeout){

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

    memset(response, '', 100);    // Initialize 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 1  is in the response of the module
            if (strstr(response, expected_answer1) != NULL)
            {
                answer = 1;
            }
            // check if the desired answer 2 is in the response of the module
            else if (strstr(response, expected_answer2) != NULL)
            {
                answer = 2;
            }
        }
    }
    // Waits for the asnwer with time out
    while((answer == 0) && ((millis() - previous) < timeout));

    return answer;
}

int8_t answer;
int onModulePin= 2;
char aux_str[50];

char ip_data[40]="Test string from GPRS shieldrn";

void setup(){

    pinMode(onModulePin, OUTPUT);
    Serial.begin(115200);

    Serial.println("Starting...");
    power_on();

    delay(3000);

    // sets the PIN code
    sendATcommand2("AT+CPIN=****", "OK", "ERROR", 2000);

    delay(3000);

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

    while( sendATcommand2("AT+CREG?", "+CREG: 0,1", "+CREG: 0,5", 1000) == 0 );

}


void loop(){


    // Selects Multi-connection mode
    if (sendATcommand2("AT+CIPMUX=1", "OK", "ERROR", 1000) == 1)
    {
        // Waits for status IP INITIAL
        while(sendATcommand2("AT+CIPSTATUS", "INITIAL", "", 500)  == 0 );
        delay(5000);

        // Sets the APN, user name and password
        if (sendATcommand2("AT+CSTT="APN","user_name","password"", "OK",  "ERROR", 30000) == 1)
        {
            // Waits for status IP START
            while(sendATcommand2("AT+CIPSTATUS", "START", "", 500)  == 0 );
            delay(5000);

            // Brings Up Wireless Connection
            if (sendATcommand2("AT+CIICR", "OK", "ERROR", 30000) == 1)
            {
                // Waits for status IP GPRSACT
                while(sendATcommand2("AT+CIPSTATUS", "GPRSACT", "", 500)  == 0 );
                delay(5000);

                // Gets Local IP Address
                if (sendATcommand2("AT+CIFSR", ".", "ERROR", 10000) == 1)
                {
                    // Waits for status IP STATUS
                    while(sendATcommand2("AT+CIPSTATUS", "IP STATUS", "", 500)  == 0 );
                    delay(5000);
                    Serial.println("Openning TCP");

                    // Opens a TCP socket with connection 1
                    if (sendATcommand2("AT+CIPSTART=1,"TCP","IP_address","port"",
                                    "CONNECT OK", "CONNECT FAIL", 30000) == 1)
                    {
                        Serial.println("Connected");

                        // Sends some data to the TCP socket
                        sprintf(aux_str,"AT+CIPSEND=1,%d", strlen(ip_data));
                        if (sendATcommand2(aux_str, ">", "ERROR", 10000) == 1)
                        {
                            delay(500);
                            sendATcommand2(ip_data, "SEND OK", "ERROR", 10000);
                        }

                        // Closes the socket
                        sendATcommand2("AT+CIPCLOSE=1", "CLOSE OK", "ERROR", 10000);
                    }
                    else
                    {
                        Serial.println("Error openning the connection 1");
                    }

                }
                else
                {
                    Serial.println("Error getting the IP address");
                }
            }
            else
            {
                Serial.println("Error bring up wireless connection");
            }
        }
        else
        {
            Serial.println("Error setting the APN");
        }
    }
    else
    {
        Serial.println("Error setting the multi-connection");
    }

    sendATcommand2("AT+CIPSHUT", "OK", "ERROR", 10000);
    delay(10000);
}

void power_on(){

    uint8_t answer=0;

    // checks if the module is started
    answer = sendATcommand2("AT", "OK", "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 = sendATcommand2("AT", "OK", "OK", 2000);
        }
    }

}

int8_t sendATcommand2(char* ATcommand, char* expected_answer1,
        char* expected_answer2, unsigned int timeout){

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

    memset(response, '', 100);    // Initialize 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 1  is in the response of the module
            if (strstr(response, expected_answer1) != NULL)
            {
                answer = 1;
            }
            // check if the desired answer 2 is in the response of the module
            else if (strstr(response, expected_answer2) != NULL)
            {
                answer = 2;
            }
        }
    }
    // Waits for the asnwer with time out
    while((answer == 0) && ((millis() - previous) < timeout));

    return answer;
}

May 13, 2014 by Dost Muhammad Shah on Electronics

latest enhance firmware for SIMCOM SIM900 module (1137B03SIM900M64_ST_ENHANCE )

In continuation to my posts regarding firmwares for SIMCOM modules , here is the latest firmware for sim900. It supports the following along with other standard features

DTMF
Jamming detection
MMS
GSM location
Email

… →

April 24, 2014 by Dost Muhammad Shah on Electronics

sim900-firmware-update-tutorials-appnotes

simcom modules firmware collection

Here I am trying to make a collection of firmware (simcom modules firmware) and release notes for Simcom Sim900 and other Simcom GSM/GPRS modules

You may upload the files that you have to share with others and they would be available in the user Uploads folder below. I may filter them time to time and put them in the relative folders.

… →

April 24, 2014 by Dost Muhammad Shah on Electronics

Disable PIN code using Gsm modem AT commands

If you have a PIN code enabled SIM card and want to remove /disable PIN code using AT commands follow these commands,
suppose 9546 is the current PIN code , Replace 9546 with your PIN code, >>> shows the response from modem.

AT+CPIN?
>>> +CPIN: SIM PIN // pin codes need to be entered
>>> OK

AT+CPIN="9546"
>>>; OK

AT+CLCK="SC",0,"9546" // disable pin code
>>> OK

AT+CPIN?
>>> +CPIN: READY

April 24, 2014 by Dost Muhammad Shah on Coding, Electronics

GSM Modem/Module not responding to AT commands after firmware Upgrade??

I get a lot of queries about this issue, so I thought I should write a small post about it. For example the latest one was

Hello Muhammad,
I recently update SIM900 to firmware 1137B12SIM900M64_ST.cla using “Simcom – sim900 Customer flash loader V1.01″ at the baud rate 1498000. Everything went perfectly like but after I restart the module I get “þIIIIþþþ” response from SIM900 at 115200 baud rate, I could not get any AT commands working. Kindly do help me.

Some modems support AutoBaud by default. Auto Baud feature allows the modem to be used with any baud rate, and for this to be used the Modem waits for a input string “ATr” it uses this string to detect the baud rate being used. As the manual describes the modem when in Auto Baud will be looking for this string after it is powered and this should be in CAPS otherwise modem wont be able to detect the correct baud rate. Sim900 has the auto baud by default. Some modems don not support Auto Baud so for these modems after the firmware has been updated, you should use the default baud rate, 9600 and 115200 are the most common.

if you want to fix or change the baud rate you should use the AT+IPR command. For example if you need to fix it to 4800.

 AT+IPR=4800r

dmSherazi

Embedded Electronics HW/SW Engineer with expertise in Hardware & Software including PCB design and Analysis, firmware development and Android development apart from causual web-development (wordpress & Laravel) and to some extent photography.

sim900