Arduino driver for GSM/GPRS+GNSS modules SIMCom SIM808/SIM868 to make HTTP/S connections with GET and POST methods and use GPS/GNSS functions
Based on: ostaquet/Arduino-SIM800L-driver
This is a comprehensive Arduino library to make HTTP or HTTPS communication and GPS/GNSS functions through the SIMCom SIM808 module. The library has been designed to limit the memory usage by working with the same shared buffer all the time.
The SIM808 is a GSM/GPRS+GNSS module built by SIMCom. The communication with the SIM808 module relies on AT commands. The available AT commands are described in the SIM800 series AT Command Manual.
Supported features in this library:
- Power management of the SIM808 module
- Network registration and signal strengh measurement
- GPRS connectivity and setup
- GPS?GNSS connectivity and setup
- HTTP and HTTPS (SSL based on in-built IP stack)
- GET and POST methods
- SoftwareSerial and HardwareSerial links
- Configurable debug serial
- Limited memory usage
- The original module is working with an input voltage of 3.7V to 4.2V. So, don't connect the naked module directly on the Arduino. I personally use a module with voltage convertors from/to 5V like this one.
- As the chipset can draw 2A maximum, it is better to use an external power source. Using the USB power through the computer is not enough while HTTP communication.
- There are different firmware version of the SIM808 on the market. The HTTPS connectivity is available only for R14 and above. (You can check your version with the examples BasicTest_HardwareSerial or BasicTest_SoftSerial)
- The firmware of the SIM808 is quite old and doesn't support the latest cryptographic protocols which could lead to some issues while connecting backends (typically errors
605and606). Read also the section below about security concerns.
The easiest way to install the library is to go to the Library manager of the Arduino IDE and install the library.
- In the Arduino IDE, go into menu Tools -> Manage Libraries...
- Search for SIM808
- Install SIM808 HTTP connector by Olivier Staquet
You will find examples in the repository to make HTTPS GET and HTTPS POST.
We are using the Postman Echo service to illustrate the communication with an external API. By the way, if you need a pretty cool tool to test and validate API, I recommend Postman. They make really API devlopment simple.
First, you have to initiate the driver by telling him the serial link and the RESET pin. The next two parameters defined the size of the internal buffer and the size of the reception buffer. The size of the reception buffer is depending on the data you will receive from the web service/API. If the buffer is too small, you will receive only the first 512 bytes in the examples below. The driver has a buffer overflow protection.
To initiate with a SoftwareSerial link (on pin TX_PIN and RX_PIN):
SoftwareSerial* serial = new SoftwareSerial(TX_PIN, RX_PIN);
serial->begin(9600);
SIM808Driver* sim808 = new SIM808Driver((Stream *)serial, SIM808_RST_PIN, 200, 512);
To initiate with a hardware serial link (Serial1):
Serial1.begin(9600);
SIM808Driver* sim808 = new SIM808Driver((Stream *)&Serial1, SIM808_RST_PIN, 200, 512);
Then, you have to initiate the basis for a GPRS connectivity.
The module has to be initalized and accept AT commands. You can test it and wait the module to be ready.
sim808->isReady();
The GSM signal should be up. You can test the signed strenght and wait for a signal greater than 0.
sim808->getSignal();
The module has to be registered on the network. You can obtain the registration status through a specific command and wait for a NET_REGISTERED_HOME or NET_REGISTERED_ROAMING depending on your operator and location.
sim808->getRegistrationStatus();
Finally, you have to setup the APN for the GPRS connectivity. By example: Internet.be for Orange Belgium who is providing SIM cards dedicated for IoT.
sim808->setupGPRS("Internet.be");
Before making any connection, you have to open the GPRS connection. It can be done easily. When the GPRS connectivity is UP, the LED is blinking fast on the SIM808 module.
sim808->connectGPRS();
In order to make an HTTP GET connection to a server or the Postman Echo service, you just have to define the URL and the timeout in milli-seconds. The HTTP or the HTTPS protocol is set automatically depending on the URL. The URL should always start with http:// or https://.
sim808->doGet("https://postman-echo.com/get?foo1=bar1&foo2=bar2", 10000);
or
sim808->doGet("https://postman-echo.com/get?foo1=bar1&foo2=bar2", "Header-1:value1\\r\\nHeader-2:value2", 10000);
If the method returns 200 (HTTP status code for OK), you can obtain the size of the data received.
sim808->getDataSizeReceived();
And you can obtain the data received through a char array.
sim808->getDataReceived();
In order to make an HTTP POST connection to a server or the Postman Echo service, you have to define a bit more information than the GET. Again, the HTTP or the HTTPS protocol is set automatically depending on the URL. The URL should always start with http:// or https://.
The arguments of the method are:
- The URL (https://postman-echo.com/post)
- (optional) Headers ("Header-1:value1\r\nHeader-2:value2")
- The content type (application/json)
- The content to POST ({"name": "morpheus", "job": "leader"})
- The write timeout while writing data to the server (10000 ms)
- The read timeout while reading data from the server (10000 ms)
sim808->doPost("https://postman-echo.com/post", "application/json", "{\"name\": \"morpheus\", \"job\": \"leader\"}", 10000, 10000);
or with headers
sim808->doPost("https://postman-echo.com/post", "Header-1:value1\\r\\nHeader-2:value2", "application/json", "{\"name\": \"morpheus\", \"job\": \"leader\"}", 10000, 10000);
If the method returns 200 (HTTP status code for OK), you can obtain the size of the data received.
sim808->getDataSizeReceived();
And you can obtain the data recieved through a char array.
sim808->getDataReceived();
At the end of the connection, don't forget to disconnect the GPRS to save power.
sim808->disconnectGPRS();