The SIM800L is a cheap and portable GSM breakout board with all the capabilities of the larger SIM900 shields. In this Arduino SIM800L tutorial, I will help you with using this nifty device. Sending and receiving texts with your Arduino have never been easier!
Here are the features of the SIM800L breakout board:
- 2G quad-band @ 850/900/1800/1900 MHz
- Receive and make calls using the speaker and microphone outputs
- Receive and send SMS
- Connect to the Internet via GPRS
- Listen to FM radio broadcasts
- Accepts AT Commands
Read more information from the SIM800L Datasheet.
Go to SIM900 Tutorial if you have that module instead
Powering the Board
Power requirements is probably the most common issue with the SIM800L. This board draws a maximum of 2 A with an input voltage of 3.7 V to 4.2 V. This means you must not connect its pins directly to a 5 V Arduino! It doesn’t even run on 3.3 V. However, its TX and RX pins are 5V tolerant.
Some YouTube videos power their modules from the Arduino UNO’s power pins which really doesn’t work for me. When on USB port, the Arduino’s 5V pin can supply a maximum of 450 mA and when on its DC Jack, about 800 mA. However, these might explain why their modules work:
their Arduino’s have internal regulators that drop the voltage to
Some also use a diode to drop the 5 V voltage to
4.3 V (assuming a silicon diode). Maybe this would solve the voltage problem, but not the current problem.
The better approach is either to use a regulator or just have the SIM800L draw from a Li-Po battery.
If selecting a voltage regulator, I recommend the LM2596S regulator module.
The LM2596S can provide a maximum 3 A to its load. You simply use a higher voltage in its input then adjust the on-board potentiometer to have 3.7 to 4.4 V for the SIM800L. Take note that the input voltage must be at least 1.5 V higher than the output.
A Li-Po battery works well too, since they provide 3.7 V. I recommend Li-Po battery with higher ampere-hour ratings so that it can provide the SIM800L’s current requirements. My network test project uses a battery to supply power to the SIM800L.
Connecting the SIM800L to Network
If the power to the SIM800L is enough, the on-board LED starts blinking. If there’s not enough power, the LED blinks for about three seconds, then turns off.
The frequency of the blinking means something:
- Every second: searching for a network.
- Every three seconds: connected to a network.
- Twice per second: connected through GPRS.
Here’s a video showing these LED indications:
Antennas are essential for this kind of module especially if your project is indoors. Without an antenna, there would not be enough transmitting power for the SIM800L to perform GSM services such as calls and SMS.
The image above is an outdoor whip antenna and I found this antenna to be more effective than the indoor helical antenna that comes with the SIM800L module:
Another type of antenna is the PCB antenna:
This type of antenna is cheaper and doesn’t take much space as that of the whip antenna. Performance wise, the PCB antenna can be as good as the whip if the design is correct.
My recommendation is to use both the indoor helical antenna and either the whip or PCB antenna.
If you are still having trouble with the SIM800L, I suggest you try out my network test project. This helps you test out if the module is really connecting to a network or is getting enough power.
SIM800L and AT Commands
Like other modems, the SIM800L communicates through AT Commands. The Arduino sends these commands serially to the SIM800L and the latter replies via the same serial port.