![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-feature-image.png?resize=1200%2C390&quality=100&strip=all&ssl=1\")
In this guide we\u2019ll cover:<\/p>\nThis post is a complete guide to the SIM900 GSM GPRS Shield with the Arduino. Learn how to send and receive SMS and how to make and receive phone calls with Arduino.<\/p>\n
<\/p>\n
In this guide we\u2019ll cover:<\/p>\n
The SIM900 GSM GPRS Shield is shown in figure below.<\/p>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-shield.jpg?resize=700%2C448&quality=100&strip=all&ssl=1\")
<\/p>\n
GSM<\/strong> stands for G<\/strong>lobal S<\/strong>ystem for M<\/strong>obile Communications and is the global standard for mobile communications.<\/p>\n GPRS<\/strong> stands for G<\/strong>eneral P<\/strong>acket R<\/strong>adio S<\/strong>ervice. GPRS is a mobile service on the 2G and 3G cellular communication.<\/p>\n The GSM GPRS shield is particularly useful as it allows to:<\/p>\n Its capabilities make it perfect for projects with Arduino like:<\/p>\n Here\u2019s some of the most important features of the shield:<\/p>\n You can check the SIM900 GSM GPRS shield on Maker Advisor<\/a> and find the best price.<\/p>\n You can use the preceding links or go directly to MakerAdvisor.com\/tools<\/a> to find all the parts for your projects at the best price!<\/p> Before getting started with your SIM900 GSM GPRS module, you need to consider some aspects about the SIM card and the shield power supply.<\/p>\n Ensure you have\u00a0coverage on a GSM 850 MHz, GSM 900 MHz, DCS 1800 MHz or PCS 1900 MHz network. By GSM we mean 2G.<\/p>\n We recommend that you use a prepaid plan or a plan with unlimited SMS for testing purposes. Otherwise, if something goes wrong, you may need to pay a huge bill for hundreds of SMS text messages sent by mistake. In this tutorial we\u2019re using a prepaid plan with unlimited SMS.<\/p>\n The shield uses the original SIM card size, not micro or nano. If you have micro or nano you may consider getting a SIM card size adapter<\/a>.<\/p>\n To use the SIM card with the shield, you need to turn off the pin lock. The easiest way to do this, is to insert the SIM card in your smartphone and turn off the pin lock in the phone security settings.<\/p>\n In my case, I needed to go through: Settings<\/strong> >\u00a0Advanced<\/strong> Settings<\/strong> >\u00a0Security<\/strong> >\u00a0SIM lock<\/strong> and turn off the lock sim card with pin.<\/p>\n The shield has a DC socket for power as shown in figure below.<\/p>\n Next to the power jack there is a toggle switch to select the power source. Next to the toggle switch on the board, there is an arrow indicating the toggle position to use an external power supply – move the toggle switch to use the external power supply as shown above.<\/p>\n To power up the shield, it is advisable to use a 5V power supply that can provide 2A as the one shown below. It can also be powered with 9V 1A, or 12V 1A.<\/p>\n You can find the right power adapter for this shield here<\/a>. Make sure you select the model with 5V and 2A.<\/p>\n The figure below shows the back of the shield. It has a holder for the SIM card and for a 3V CR1220 battery for the RTC (real time clock).<\/p>\n The figure below shows the shield most important components on the board that you need to pay attention to.<\/p>\n 1)<\/strong> Insert the SIM card into the SIM card holder – make sure you’ve read the preliminary steps in the previous section. 3)\u00a0<\/strong>On the serial port select, make sure the jumper cap is connected as shown in figure below to use software serial.<\/p>\n 5)\u00a0<\/strong>To power up\/down the shield press the power key for about 2 seconds.<\/p>\n Note:\u00a0<\/strong>you can automatically turn on the shield via software. See how to do that in the Automatically turn on the shield<\/strong> section, after the code examples.<\/p>\n 7)\u00a0<\/strong>You can test if the shield is working properly by sending AT commands from the Arduino IDE using an FTDI programmer – as we’ll shown later in this guide.<\/p>\n For more information, you can check the SIM900 AT commands manual here<\/a>.<\/p>\n To test if everything is working properly, you can test the shield by sending AT commands from the Arduino IDE serial monitor. For that, you need an FTDI programmer as the one shown in figure below. You can get an FTDI programmer like this here<\/a>.<\/p>\n 1)\u00a0<\/strong>Connect the FTDI programmer to the GSM shield as shown in figure below.<\/p>\n 2)\u00a0<\/strong>Open the Arduino IDE and select the right COM port.<\/p>\n 3)\u00a0<\/strong>Open the Serial monitor\u00a0 4)\u00a0<\/strong>Select 19200<\/strong> <\/span>baud rate – the shield default setting is 19200 – and Carriage return<\/strong>.<\/strong><\/span> Write AT<\/strong> at the box highlighted in red and then press enter. See figure below.\u00a0 5)\u00a0<\/strong><\/span><\/span>The shield will respond with OK<\/strong>, if everything is working properly.<\/p>\n Connect the shield to the Arduino as shown in the schematics below.<\/p>\n To send an SMS, upload the code below to your Arduino board.<\/p>\n View raw code<\/a><\/p>\n In this code, \u00a0you start by \u00a0including the SoftwareSerial.h<\/strong> library and create a software serial port on pins 7 and 8. (Pin 7 is being set as RX and 8 as TX)<\/p>\n The sendSMS()<\/strong> function created is what actually sends the SMS. This function uses the AT commands: AT+CMGF=1\\<\/strong>r\u00a0and\u00a0AT + CMGS<\/strong>.<\/p>\n You need to change the recipient’s mobile number at: (replace the X<\/strong><\/span>‘s with the recipient’s phone number)<\/p>\n The recipient’s mobile number should be in international format.<\/p>\n Then, at the following line you can edit the text you want to send.<\/p>\n To read incoming SMS, upload the code below to your Arduino. After uploading, wait 20 seconds for the shield to establish communication. Then, test the script by sending an SMS to the shield SIM card number. The SMS is shown on the Arduino serial monitor – baud rate: 19200.<\/p>\n View raw code<\/a><\/p>\n In this code, you set the module to send the SMS data to the serial output:<\/p>\n You store the incoming characters from the SMS message on the incoming_char<\/strong> variable. You read the chars using the SIM900.read()<\/strong> function.<\/p>\n To make a phone call, upload the following code to your Arduino.<\/p>\n Don’t forget to edit the code with the phone number you want to call.<\/strong><\/span><\/p>\n View raw code<\/a><\/p>\n To make the call, you use the callSomeone()<\/strong> function that uses the ATD<\/strong> command.<\/p>\n You need to replace the X<\/strong><\/span>‘s (highlighted in red) with the phone number you want to call.<\/p>\n Don’t forget to connect a microphone and earphones to make the call.<\/p>\n In this code example, the call is hang up after 30 seconds, using the ATH<\/strong> command:<\/p>\n Hanging up after 30 seconds is not very useful, but it works well for an example. The idea is that you use the ATH<\/strong> command when an event is triggered. For example, connect a push button to the Arduino, that when pressed sends the ATH<\/strong> command to hang up the phone.<\/p>\n The following code answers incoming calls.<\/p>\n View raw code<\/a><\/p>\n When someone calls the SIM900 number, it sends a message saying “RING”. To know if someone is calling you, you can wait for incoming characters from the SIM900 and then, compare if it was a RING message. \u00a0That’s what is done in this code.\u00a0When it receives a RING message, you send the ATA<\/strong> command to answer the phone.<\/p>\n Instead of manually pressing the “power” key to turn on the shield, you can automatically turn on the shield via software.<\/p>\n 1) <\/strong>First, you need to solder R13 connections on the shield as shown in the figure below – highlighted in red.<\/p>\n 2)<\/strong> Connect D9 on the shield to the D9 Arduino pin as shown in the schematic below.<\/p>\n 3)\u00a0<\/strong>Add the following code snippet in the setup() function. This is\u00a0the equivalent of pressing the shield \u201cpower\u201d button.<\/p>\n Shield doesn’t respond with OK<\/strong><\/p>\n Check your TX and RX connections to the Arduino. Try repeating the process by changing the TX with the RX pins.<\/p>\n Also check if you have selected the software serial by placing the jumper cap on the appropriate place on the serial selector.<\/p>\n Cannot see messages in the serial monitor<\/strong><\/p>\n To see the messages in the serial monitor, the shield and the Arduino’s serial port baud rate should be the same. The SIM900 GSM GPRS shield default baud rate is 19200. So, select the Arduino’s baud rate to 19200.<\/p>\n However, if you need to change the shield baud rate, you can send the following AT command to change it to 19200 or other appropriate baud rate.<\/p>\n This tutorial shows you how to send and receive SMS and making and receiving phone calls with the Arduino. You can apply the concepts learned in this tutorial to build your own projects to communicate over a cell network. We have other projects that use GSM, check them below:<\/p>\n If you like Arduino projects, make sure you check our latest Arduino:\u00a0Arduino Step-by-step Projects \u2013 Build 25 Projects<\/a><\/strong><\/p>\n We hope you\u2019ve found this guide useful.<\/p>\n Thanks for reading.<\/p>\n","protected":false},"excerpt":{"rendered":" This post is a complete guide to the SIM900 GSM GPRS Shield with the Arduino. Learn how to send and receive SMS and how to make and receive phone calls … <\/p>\nApplications:<\/h3>\n
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Features<\/h3>\n
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![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/RTC-battery-holder.jpg?resize=400%2C272&quality=100&strip=all&ssl=1\")
<\/p>\n\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/jacks.jpg?resize=521%2C242&quality=100&strip=all&ssl=1\")
<\/p>\nWhere to buy?<\/h3>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/09\/gsm-shield-1.jpg?resize=226%2C305&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\nPreliminary steps<\/h2>\n
GSM coverage<\/h3>\n
Prepaid SIM Card<\/h3>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/SIM-card.jpg?resize=496%2C279&quality=100&strip=all&ssl=1\")
<\/p>\nTurn off the PIN lock<\/h3>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/Screenshot_2017-08-25-09-05-25.png?resize=700%2C379&quality=100&strip=all&ssl=1\")
<\/p>\nGetting the right power supply<\/h3>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/DC-jack.png?resize=699%2C398&quality=100&strip=all&ssl=1\")
<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/power-adapter.jpg?resize=481%2C440&quality=100&strip=all&ssl=1\")
<\/p>\nSIM900 GSM GPRS Shield Hardware<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/DSC01078-Copy.jpg?resize=700%2C504&quality=100&strip=all&ssl=1\")
<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-shield-labels.png?resize=925%2C538&quality=100&strip=all&ssl=1\")
<\/a><\/p>\nGetting started<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/insert-SIM.jpg?resize=700%2C245&quality=100&strip=all&ssl=1\")
2)\u00a0<\/strong>Make sure the antenna is well connected.<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/software-serial.jpg?resize=700%2C296&quality=100&strip=all&ssl=1\")
4)\u00a0<\/strong>Power the shield using an external 5V power supply. Make sure you select the external power source with the toggle switch next to the DC jack.<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/power-select.png?resize=338%2C227&quality=100&strip=all&ssl=1\")
<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/power-key.png?resize=329%2C212&quality=100&strip=all&ssl=1\")
6)\u00a0<\/strong>Then, the Status LED will light up and the NetLight LED will blink every 800 ms until it finds the network. When it finds the network, the NetLight LED will start blinking every three seconds.<\/p>\nSIM900 AT commands<\/h2>\n
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Testing the Shield with FTDI programmer<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/FTDI.jpg?resize=404%2C171&quality=100&strip=all&ssl=1\")
<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-FTDI-circuit-1.png?resize=1066%2C754&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/serial-monitor.png?resize=745%2C109&quality=100&strip=all&ssl=1\")
<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-arduino-ide-serial-monitor-set-baud-rate.png?resize=559%2C315&quality=100&strip=all&ssl=1\")
<\/span><\/span><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-arduino-ide-serial-monitor-Copy.png?resize=559%2C306&quality=100&strip=all&ssl=1\")
<\/p>\nConnecting the Shield to Arduino<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/08\/GSM-Arduino-circuit.png?resize=1164%2C772&quality=100&strip=all&ssl=1\")
<\/a><\/p>\nSending an SMS<\/h2>\n
\/*********\n Complete project details at http:\/\/randomnerdtutorials.com \n*********\/\n\n#include <SoftwareSerial.h>\n\n\/\/ Configure software serial port\nSoftwareSerial SIM900(7, 8); \n\nvoid setup() {\n \/\/ Arduino communicates with SIM900 GSM shield at a baud rate of 19200\n \/\/ Make sure that corresponds to the baud rate of your module\n SIM900.begin(19200);\n \/\/ Give time to your GSM shield log on to network\n delay(20000); \n \n \/\/ Send the SMS\n sendSMS();\n}\n\nvoid loop() { \n \n}\n\nvoid sendSMS() {\n \/\/ AT command to set SIM900 to SMS mode\n SIM900.print("AT+CMGF=1\\r"); \n delay(100);\n\n \/\/ REPLACE THE X's WITH THE RECIPIENT'S MOBILE NUMBER\n \/\/ USE INTERNATIONAL FORMAT CODE FOR MOBILE NUMBERS\n SIM900.println("AT+CMGS=\\"+XXXXXXXXXXXX\\""); \n delay(100);\n \n \/\/ REPLACE WITH YOUR OWN SMS MESSAGE CONTENT\n SIM900.println("Message example from Arduino Uno."); \n delay(100);\n\n \/\/ End AT command with a ^Z, ASCII code 26\n SIM900.println((char)26); \n delay(100);\n SIM900.println();\n \/\/ Give module time to send SMS\n delay(5000); \n}\n<\/code><\/pre>\n\t#include <SoftwareSerial.h>\nSoftwareSerial SIM900(7, 8);<\/strong><\/pre>\n
SIM900.println(\"AT + CMGS = \\\"++++++++++++++<\/span>\"\");<\/strong><\/pre>\n\/\/ REPLACE WITH YOUR OWN SMS MESSAGE CONTENT\nSIM900.println(\"Message example from Arduino Uno.<\/span>\")<\/strong><\/pre>\nReading received SMS<\/h2>\n
\/*********\n Complete project details at http:\/\/randomnerdtutorials.com \n*********\/\n\n#include <SoftwareSerial.h>\n\n\/\/ Configure software serial port\nSoftwareSerial SIM900(7, 8);\n\/\/Variable to save incoming SMS characters\nchar incoming_char=0;\n\nvoid setup() {\n \/\/ Arduino communicates with SIM900 GSM shield at a baud rate of 19200\n \/\/ Make sure that corresponds to the baud rate of your module\n SIM900.begin(19200);\n \/\/ For serial monitor\n Serial.begin(19200); \n \/\/ Give time to your GSM shield log on to network\n delay(20000);\n\n \/\/ AT command to set SIM900 to SMS mode\n SIM900.print("AT+CMGF=1\\r"); \n delay(100);\n \/\/ Set module to send SMS data to serial out upon receipt \n SIM900.print("AT+CNMI=2,2,0,0,0\\r");\n delay(100);\n}\n\nvoid loop() {\n \/\/ Display any text that the GSM shield sends out on the serial monitor\n if(SIM900.available() >0) {\n \/\/Get the character from the cellular serial port\n incoming_char=SIM900.read(); \n \/\/Print the incoming character to the terminal\n Serial.print(incoming_char); \n }\n}\n<\/code><\/pre>\n\tSIM900.print(\"AT+CNMI=2,2,0,0,0\\r\");<\/strong><\/pre>\n
Making a phone call<\/h2>\n
\/*********\n Complete project details at http:\/\/randomnerdtutorials.com \n*********\/\n\n#include <SoftwareSerial.h>\n\n\/\/ Configure software serial port\nSoftwareSerial SIM900(7, 8); \n\nvoid setup() {\n \/\/ Arduino communicates with SIM900 GSM shield at a baud rate of 19200\n \/\/ Make sure that corresponds to the baud rate of your module\n SIM900.begin(19200);\n \/\/ Give time to your GSM shield log on to network\n delay(20000);\n\n \/\/ Make the phone call\n callSomeone();\n}\n\nvoid loop() {\n \n}\n\nvoid callSomeone() {\n \/\/ REPLACE THE X's WITH THE NUMER YOU WANT TO DIAL\n \/\/ USE INTERNATIONAL FORMAT CODE FOR MOBILE NUMBERS\n SIM900.println("ATD + +XXXXXXXXX;");\n delay(100);\n SIM900.println();\n \n \/\/ In this example, the call only last 30 seconds\n \/\/ You can edit the phone call duration in the delay time\n delay(30000);\n \/\/ AT command to hang up\n SIM900.println("ATH"); \/\/ hang up\n}\n<\/code><\/pre>\n\tSIM900.println(\"ATD + +XXXXXXXXX<\/span>;\");<\/strong><\/pre>\nSIM900.println(\"ATH\"); \n<\/strong><\/pre>\n
Answering incoming phone calls<\/h2>\n
\/*********\n Complete project details at http:\/\/randomnerdtutorials.com \n*********\/\n\n#include <SoftwareSerial.h>\n\n\/\/ Configure software serial port\nSoftwareSerial SIM900(7, 8); \nchar incoming_char=0;\n\nvoid setup() {\n \/\/ Arduino communicates with SIM900 GSM shield at a baud rate of 19200\n \/\/ Make sure that corresponds to the baud rate of your module\n SIM900.begin(19200); \/\/ for GSM shield\n \/\/ For serial monitor\n Serial.begin(19200); \n \/\/ Give time to log on to network.\n delay(20000); \n \n SIM900.print("AT+CLIP=1\\r"); \/\/ turn on caller ID notification\n delay(100);\n}\n\nvoid loop() {\n \/\/ Display any text that the GSM shield sends out on the serial monitor\n if(SIM900.available() >0) {\n \/\/ Get the character from the cellular serial por\n \/\/ With an incomming call, a "RING" message is sent out\n incoming_char=SIM900.read();\n \/\/ Check if the shield is sending a "RING" message\n if (incoming_char=='R') {\n delay(10);\n Serial.print(incoming_char);\n incoming_char=SIM900.read();\n if (incoming_char =='I') {\n delay(10);\n Serial.print(incoming_char);\n incoming_char=SIM900.read();\n if (incoming_char=='N') {\n delay(10);\n Serial.print(incoming_char);\n incoming_char=SIM900.read();\n if (incoming_char=='G') {\n delay(10);\n Serial.print(incoming_char);\n \/\/ If the message received from the shield is RING\n \/\/ Send ATA commands to answer the phone\n SIM900.print("ATA\\r");\n }\n }\n }\n }\n }\n}\n<\/code><\/pre>\n\tAutomatically turn on the shield<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/R13.jpg?resize=685%2C338&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/GSM-Arduino-circuit.jpg?resize=1200%2C738&quality=100&strip=all&ssl=1\")
<\/a><\/p>\ndigitalWrite(9, HIGH);\ndelay(1000);\ndigitalWrite(9, LOW);\ndelay(5000);<\/pre>\n
Troubleshooting<\/h2>\n
<\/p>\nAT+IPR=19200<\/strong><\/pre>\n
Wrapping up<\/h2>\n
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