Arduino ShieldGPRS GSM SIM900 Arduino Shield
Maximize The GPRS Shield provides you a way to use the GSM cell phone network to receive data from a remote location. The shield allows you to achieve this via any of the three methods:
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The GPRS Shield provides you a way to use the GSM cell phone network to receive data from a remote location. The shield allows you to achieve this via any of the three methods:
The GPRS Shield is compatible with all boards which have the same form factor (and pinout) as a standard Arduino Board. The GPRS Shield can be configured and controlled through UART by simple AT commands. Based on the SIM900 module from SIMCOM, the GPRS Shield is like a cell phone. Besides the communications features, the GPRS Shield has 12 GPIOs, 2 PWMs and an ADC.
For SIM900’s Specifications, please refer this PDF file: SIM900_SPEC.pdf
| Item | Min | Typical | Max | Unit |
|---|---|---|---|---|
| Voltage | 4.8 | 5.0 | 5.2 | VDC |
| Current | / | 50 | 450 | mA |
| Dimension(with antenna) | 110x58x19 | mm | ||
| Net Weight | 76±2 | g | ||
We have produced a lot of extension boards that can make your platform board more powerful, however not every extension board is compatible with all the platform boards, we use a table to illustrate how are those boards compatible with platform boards.
Note
Please note that “Not recommended” means that it might have chance to work with the platform board however requires extra work such as jump wires or rewriting the code. If you are interested in digging more, welcome to contact with [email protected].
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| LED | State | Function |
|---|---|---|
| Status | Off | Power Off |
| On | Power On | |
| Netlight | Off | SIM900 is not working |
| 64ms On/800ms Off | SIM900 does not find the network | |
| 64ms On/3000ms Off | SIM900 finds the network | |
| 64ms On/300ms Off | GPRS communication |
Insert an unlocked SIM card into SIM Card Holder - 6 Pin Holder for SIM Cards. Both 1.8 volts and 3.0 volts SIM Cards are supported by SIM900 - voltage type of the SIM card is automatically detected.
Make sure the antenna pad buckled properly - A miniature coaxial RF connector is presented on the GPRS Shield board to connect a GSM Antenna. The connector presented on the GPRS Shield is called a U.FL connector. The GSM The Antenna being attached on the GPRS Shield has an SMA connector (and not an RP-SMA connector) on it. A patch cord is also supplied with the GPRS Shield to interface the antenna to the board. The connection topology is shown in the diagram below:
| GPRS communicate with arduino by software serial | GPRS communicate with arduino by hardware serial |
|---|---|
 |  |
Hardware trigger Press the power key for about 2 seconds to power up or power down.
Software trigger You can power up/down the shield through D9 pin of Arduino by adding software triggering in your firmware.
Note
The JP for pin 9 on the shield must be soldered in order to use software power up/down.
As the timing of turn on/off , a >1s pulse was needed to trigger the turning, and a >3.2s delay was needed to get the timing stable. The following code in your firmware is required to turn on / off the shield without pressing the button:
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void powerUpOrDown() { pinMode(9, OUTPUT); digitalWrite(9,LOW); delay(1000); digitalWrite(9,HIGH); delay(2000); digitalWrite(9,LOW); delay(3000); } The GPRS Shield comes with all the accessories that you need to get started with sending data over the GSM network except an Arduino board and a GSM SIM Card. If you want to make voice calls, you would also require a headset with microphone.
Step 1: Creating a test setup for the GPRS Shield
As you received your GPRS Shield, what would be the first thing you want to do with it? Send out a text (SMS)? or call up someone (headset required)? You can do all of these by talking to the GPRS Shield through AT Commands - which is a special language that it understands. AT Commands are simple textual commands sent to the GPRS modem over its serial interface (UART), so you can use any serial terminal software to communicate with it.
Note
Almost all the AT commands should be sent by following with carriage return and you need to select the “+CR”option in the serial port terminal.
To do experiment with AT commands, you would require a way to power up and communicate with your GPRS Shield. The best way to do this using an Arduino Duemilanove board described below. The same steps are applicable for Seeeduino or Seeeduino Stalker.
For developing such a program, we need to use the SoftwareSerial library. Here is the demo code.
//Serial Relay - Arduino will patch a //serial link between the computer and the GPRS Shield //at 19200 bps 8-N-1 //Computer is connected to Hardware UART //GPRS Shield is connected to the Software UART #include <SoftwareSerial.h> SoftwareSerial GPRS(7, 8); unsigned char buffer[64]; // buffer array for data recieve over serial port int count=0; // counter for buffer array void setup() { GPRS.begin(19200); // the GPRS baud rate Serial.begin(19200); // the Serial port of Arduino baud rate. } void loop() { if (GPRS.available()) // if date is comming from softwareserial port ==> data is comming from gprs shield { while(GPRS.available()) // reading data into char array { buffer[count++]=GPRS.read(); // writing data into array if(count == 64)break; } Serial.write(buffer,count); // if no data transmission ends, write buffer to hardware serial port clearBufferArray(); // call clearBufferArray function to clear the storaged data from the array count = 0; // set counter of while loop to zero } if (Serial.available()) // if data is available on hardwareserial port ==> data is comming from PC or notebook GPRS.write(Serial.read()); // write it to the GPRS shield } void clearBufferArray() // function to clear buffer array { for (int i=0; i<count;i++) { buffer[i]=NULL;} // clear all index of array with command NULL } 
Also, you should see messages from the shield such as RDY +CFUN: 1 +CPIN: READYCall Readyin the serial monitor. If you can not see the messages in the serial monitor, you should click the “send new” option that will add carriage return at the end of AT command and then send AT command “AT+IPR=19200” to set the baud rate of the SIM900.
Note that the baud rate of GPRS shield and the Arduino’s serial port should be the same before you setting the GPRS shield’s baud rate.
Step 2: Sending a text message (SMS)
Now that our test setup is ready, let’s play around with some AT Commands manually before moving on to program the Arduino to do this. Let’s try sending an SMS to start.
Note
If you follow steps as specified above, you aren’t able to receive the message on the target handset, then it might be that you need to set the SMS Message Center number.
Send the command AT+CSCA=”+919032055002” and press the Enter Key. Send this command in between the AT+CMGF and AT+CMGS commands. Replace the phone number specified in the command above with the SMS Center number of your GSM Service Provider.
The message center number is specific to each service provider (for example +919032055002 is the message center number for Tata DoCoMo, Pune, India). You can get the message center number by calling up the customer center of the GSM Service Provider and asking them for it.
Step 3: Exploring further
Now that you have gotten a taste of how the AT Commands work, you can try out other commands before moving on to develop sketches for Arduino by using the GPRS Shield.
This involves to create a sketch for sending out these same sequence of AT Commands (on your behalf) out the serial port to the GPRS Shield to perform the same task of sending and SMS, making a call or sending data over a GPRS connection.
You can go through the AT Commands reference manual to figure out the sequence of commands. If you develop an Arduino sketch, you find that the GPRS Shield doesn’t act as what you expect, then you will need to check your AT Commands and their sequence. To do this, reload the serial relay sketch attached above in the getting started section into ATmega328P and type out the AT Commands manually and check the output. The responses sent back by the GPRS Shield will help you debug the AT Command sequence.
Note
A C program to perform the same task has also been developed and attached: Softuart relay atmega328p.zip.
The program was developed on a Windows PC.AVRStudio4 was used as the IDE and WinAVR was used as the compiler. The ZIP file contains an AVRStudio4 Project. The C compiler (WinAVR) will generate an Intel Hex (.hex). To upload this .hex file into an Arduino board outside of Arduino IDE would require a program which is able to communicate with the Arduino boards bootloader. XLoader is such a program which runs on Windows can upload .hex files generated by various compiler into an Arduino Board.
With Arduino 1.0 you should be able to use the SoftwareSerial library included with the distribution (instead of NewSoftSerial). However, you must be aware that the buffer reserved for incoming messages are hardcoded to 64 bytes in the library header, “SoftwareSerial.h”:
define _SS_MAX_RX_BUFF 64 // RX buffer size This means that if the GPRS module receive more data than the buffer, you are likely to lose it with a buffer overflow! For instance, reading out an SMS from the module with “AT+CMGR=xx” (xx is the message index), you might not even see the message part because the preceding header information (like telephone number and time) takes up a lot of space. The fix seems to be to manually change _SS_MAX_RX_BUFF to a higher value (but reasonable so you don’t use all your memory!)
The Softwareserial library has the following limitations (taken from arduino page). If use multiple software serial ports, only one can receive data at a time. This means that if you try to add another serial device such as grove serial LCD you may get communication errors unless you craft your code carefully.
The below demo code is for the Xduino to send SMS message, dial a voice call, submit a http request to a website and upload data to the pachube. It has been tested on Arduino Duemilanove and also works on any compatible platforms, please note that this sketch uses the software UART of ATmega328P. please follow the below steps to run this sketch.
Type command in the terminal to execute different function, there are 4 functions in the demo:
If the program returns error in the terminal after you typing the command, don’t worry, just try input the command again.
/*Note: this code is a demo for how to using gprs shield to send sms message, dial a voice call and send a http request to the website, upload data to pachube.com by TCP connection, The microcontrollers Digital Pin 7 and hence allow unhindered communication with GPRS Shield using SoftSerial Library. IDE: Arduino 1.0 or later Replace the following items in the code: 1.Phone number, don't forget add the country code 2.Replace the Access Point Name 3. Replace the Pachube API Key with your personal ones assigned to your account at cosm.com */ #include <SoftwareSerial.h> #include <String.h> SoftwareSerial mySerial(7, 8); void setup() { mySerial.begin(19200); // the GPRS baud rate Serial.begin(19200); // the GPRS baud rate delay(500); } void loop() { //after start up the program, you can using terminal to connect the serial of gprs shield, //if you input 't' in the terminal, the program will execute SendTextMessage(), it will show how to send a sms message, //if input 'd' in the terminal, it will execute DialVoiceCall(), etc. if (Serial.available()) switch(Serial.read()) { case 't': SendTextMessage(); break; case 'd': DialVoiceCall(); break; case 'h': SubmitHttpRequest(); break; case 's': Send2Pachube(); break; } if (mySerial.available()) Serial.write(mySerial.read()); } ///SendTextMessage() ///this function is to send a sms message void SendTextMessage() { mySerial.print("AT+CMGF=1\r"); //Because we want to send the SMS in text mode delay(100); mySerial.println("AT + CMGS = "+86138xxxxx615"");//send sms message, be careful need to add a country code before the cellphone number delay(100); mySerial.println("A test message!");//the content of the message delay(100); mySerial.println((char)26);//the ASCII code of the ctrl+z is 26 delay(100); mySerial.println(); } ///DialVoiceCall ///this function is to dial a voice call void DialVoiceCall() { mySerial.println("ATD + +86138xxxxx615;");//dial the number delay(100); mySerial.println(); } ///SubmitHttpRequest() ///this function is submit a http request ///attention:the time of delay is very important, it must be set enough void SubmitHttpRequest() { mySerial.println("AT+CSQ"); delay(100); ShowSerialData();// this code is to show the data from gprs shield, in order to easily see the process of how the gprs shield submit a http request, and the following is for this purpose too. mySerial.println("AT+CGATT?"); delay(100); ShowSerialData(); mySerial.println("AT+SAPBR=3,1,"CONTYPE","GPRS"");//setting the SAPBR, the connection type is using gprs delay(1000); ShowSerialData(); mySerial.println("AT+SAPBR=3,1,"APN","CMNET"");//setting the APN, the second need you fill in your local apn server delay(4000); ShowSerialData(); mySerial.println("AT+SAPBR=1,1");//setting the SAPBR, for detail you can refer to the AT command mamual delay(2000); ShowSerialData(); mySerial.println("AT+HTTPINIT"); //init the HTTP request delay(2000); ShowSerialData(); mySerial.println("AT+HTTPPARA="URL","www.google.com.hk"");// setting the httppara, the second parameter is the website you want to access delay(1000); ShowSerialData(); mySerial.println("AT+HTTPACTION=0");//submit the request delay(10000);//the delay is very important, the delay time is base on the return from the website, if the return datas are very large, the time required longer. //while(!mySerial.available()); ShowSerialData(); mySerial.println("AT+HTTPREAD");// read the data from the website you access delay(300); ShowSerialData(); mySerial.println(""); delay(100); } ///send2Pachube()/// ///this function is to send the sensor data to the pachube, you can see the new value in the pachube after execute this function/// void Send2Pachube() { mySerial.println("AT+CGATT?"); delay(1000); ShowSerialData(); mySerial.println("AT+CSTT="CMNET"");//start task and setting the APN, delay(1000); ShowSerialData(); mySerial.println("AT+CIICR");//bring up wireless connection delay(3000); ShowSerialData(); mySerial.println("AT+CIFSR");//get local IP adress delay(2000); ShowSerialData(); mySerial.println("AT+CIPSPRT=0"); delay(3000); ShowSerialData(); mySerial.println("AT+CIPSTART="tcp","api.cosm.com","8081"");//start up the connection delay(2000); ShowSerialData(); mySerial.println("AT+CIPSEND");//begin send data to remote server delay(4000); ShowSerialData(); String humidity = "1031";//these 4 line code are imitate the real sensor data, because the demo did't add other sensor, so using 4 string variable to replace. String moisture = "1242";//you can replace these four variable to the real sensor data in your project String temperature = "30";// String barometer = "60.56";// mySerial.print("{"method": "put","resource": "/feeds/42742/","params"");//here is the feed you apply from pachube delay(500); ShowSerialData(); mySerial.print(": {},"headers": {"X-PachubeApiKey":");//in here, you should replace your pachubeapikey delay(500); ShowSerialData(); mySerial.print(" "_cXwr5LE8qW4a296O-cDwOUvfddFer5pGmaRigPsiO0");//pachubeapikey delay(500); ShowSerialData(); mySerial.print("jEB9OjK-W6vej56j9ItaSlIac-hgbQjxExuveD95yc8BttXc");//pachubeapikey delay(500); ShowSerialData(); mySerial.print("Z7_seZqLVjeCOmNbEXUva45t6FL8AxOcuNSsQS"},"body":"); delay(500); ShowSerialData(); mySerial.print(" {"version": "1.0.0","datastreams": "); delay(500); ShowSerialData(); mySerial.println("[{"id": "01","current_value": "" + barometer + ""},"); delay(500); ShowSerialData(); mySerial.println("{"id": "02","current_value": "" + humidity + ""},"); delay(500); ShowSerialData(); mySerial.println("{"id": "03","current_value": "" + moisture + ""},"); delay(500); ShowSerialData(); mySerial.println("{"id": "04","current_value": "" + temperature + ""}]},"token": "lee"}"); delay(500); ShowSerialData(); mySerial.println((char)26);//sending delay(5000);//waitting for reply, important! the time is base on the condition of internet mySerial.println(); ShowSerialData(); mySerial.println("AT+CIPCLOSE");//close the connection delay(100); ShowSerialData(); } void ShowSerialData() { while(mySerial.available()!=0) Serial.write(mySerial.read()); } Here is the GPRS Shield FAQ that list the frequently asked questions, please read it before use:
Why does GPRS Shield can not work with Stalker v2.1/2.0 via software serial port(D7/D8) ?
Talker v2.1/2.0 has used the Digital Pin(D7/D8) , you need to connect GPRS_TX/GPRS_RX to other Digital Pin as software serial port. And this problem had been solved at Stalker 2.2 version.
Why does the I2C can’t be used when I assembled the GPRS Shield to Stalker or other Arduino boards ?
Because GPRS Shield conflicts with other module via I2C . GPRS Shield doesn’t use I2C port, you can disconnect the connection from SIM900 I2C port to A4/A5 .
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