Hello everyone, and welcome to another tutorial Sponsored by: DigitSpace
Product used: SIM800L Module Replace SIM900A GSM GPRS 5V Serial with Antenna
This tutorial is a follow up of two previous ones, make sure to check them, to be able to use the SIM800L module easily:
- Send SMS/Text from Arduino using SIM800L GSM/GPRS Module [DigitSpace.com]
- Arduino SIM800L – Dial phone numbers & LASER Tripwire GSM Alarm project [DigitSpace.com]
So on this one we gonna first check how to receive SMS/Text and displays it on the Arduino IDE Serial monitor, and as a project we gonna request data to be sent to us all via SMS: I’ll add two sensors (as example) DHT11 and MLX90614 Contactless thermal sensor, and I’ll send a SMS from my phone containing “DHT” or “MLX” and Arduino will have to look for one of those keywords within the received SMS, and then send the measured values, depending on which sensor the user chosed, by SMS to the programmed phone number.
You can use your own modules, the number of them, send multiple SMS…. it all depends on you, give it a try.
Yes I use this in pretty much all tutorials related to SIM800L, because it’s easy to forget about, the SIM card you are using shouldn’t be protected with a “pin code”, if it’s the case you can either put it in your phone for example and deactivate the “sim lock” from the phone… Or you can use the suitable “AT command” to enter the pincode from Arduino directly which is “AT+CPIN”, I didn’t use this last method but here you can find all “AT commands” to use the module:
Another thing that some may forget about is that your SIM card should have enough credit to be able to send a SMS, it depends on your network provider.
Enough talking… Let’s check our stuffs
So this is the module I used it’s the EVB version, there are several versions and in the codes things can change so be careful.
Module pinout, the wires used are 5V/Gnd for power, and then TXD/RXD/GND to communicate with Arduino.
And also as I did before, I’m powering the module using a 7.5V Lipo battery, with a Buck converter to be able to power the module with 5V, so before I powered the module directly from Arduino but it was sketchy… so I switched to external power source.
In the test#1 we gonna use a direct wiring with Arduino, set the module on the receiving SMS mode, set the way to handle the SMS received and then show it on the Arduino IDE Serial monitor.
You won’t need any external libraries for this, only the default SoftwareSerial.
So the code basically just sets the module on the receiving SMS mode, sets the way to handle the SMS in the “Setup()”, but on the loop it uses a function that permits the user to check the feedback from the SIM800L and also send Commands from the serial monitor, and as we told the module to transfert the received SMS via Serial to Arduino, we gonna print the SMS received on the Serial monitor.
Sorry the website built-in editor doesn’t have a good code editor to be able to copy it correctly, so I uploaded it to Google Drive… I’ll try to upgrade this soon.
The code contains a lot of comments to help you.
Click to expand/zoom the pictures
So here’s the project, now we can receive the SMS and transfert it to the Arduino board, but we need to detect certain kewords within the SMS, to be able to chose which sensor data is requested, do the measures and send the Data via SMS.
Two libraries should be add (Because of the modules), modules you use will define which libraries to use.
So the code is actually where the tricky part is, the SMS received should be stored in a “char” type variable but then we have to change it to “String” to be able to search the keywords within the SMS.
The code contains a lot of comments to help you understand.
Here’s a look from the code as you can see a lot of comments, and those are pretty much the tricks I did to able to achieve the objective, if you have better ones please share it with us.
Click on the pictures to expand/zoom
Send SMS from phone containg DHT and Arduino replies back with DHT11 sensor values
- You can improve the code, because that’s the trick that worked for me, maybe you have a better one, I’m sure there’s a better way.
- You can do multiple readings + averaging before sending the SMS.
- Improve the keyword detection so things like the last SMS won’t be counted
- Add some commands to clear the SIM800L memory
- Send “Error SMS” if a sensor is not working properly
Well that’s all folks a big thanks to DigitSpace for their sponsorship.
Automation and Electrical Engineer, Electronics amateur trying to share my little projects.