B4R Tutorial GSM / GPRS - Control the Arduino with SMS messages

Erel · May 11, 2016

The GSM shield allows the Arduino to connect to cellular networks. This opens the door for many interesting outdoor solutions.

There are all kinds of shields available. Make sure that the shield you are using is configured to work with pins other than 0 and 1 (which are used for programming the Arduino). We will use SoftwareSerial with AsyncStreams to communicate with the GSM module.

The GSM shield is controlled with AT commands. There are many online resources about the supported commands. Here is a one: http://www.codeproject.com/Articles/85636/Introduction-to-AT-commands-and-its-uses

The GSM code module, included in the attached example, implements the most common commands.

- Sending and receiving SMS messages.
- Making phone calls (the speaker part is not implemented).
- Incoming phone calls.
- Checking the registration status.

Only one task can be done at a time. So there is a "busy" flag that is set and cleared to make sure that commands do not mix.

In this specific example the led is controlled with SMS messages. The button sends a "click!!!" message:

B4X:

Sub btn_StateChanged (State As Boolean)
   If State = False Then
     GSM.SendSMS(phoneNumber, "Click!!!")
   End If
End Sub

Sub MessageArrived(msg() As Byte)
   If msg = "On" Then
     led.DigitalWrite(True)
   Else if msg = "Off" Then
     led.DigitalWrite(False)
   Else
     Log("error: ", msg)
   End If
End Sub

Useful information about these shields:
http://www.seeedstudio.com/wiki/GPRS_Shield_V1.0
http://www.seeedstudio.com/wiki/GPRS_Shield_V2.0

Tayfur · Nov 24, 2016

I SOLVED, pin9 on GSM BOARD.
yhank you for helps @Erel @ta1dr

https://www.b4x.com/android/forum/threads/gprs-shield-power-up-down-with-code.73348/

roberto64 · Jul 15, 2017

Hi Erel,
How can I convert the GSM module so that I can carry it to B4J, I'm experimenting with an example with B4J to connect with my smartphone and send and receive messages directly from B4J.
Greetings

Erel · Jul 16, 2017

roberto64 said:
smartphone and send and receive messages directly from B4J.

Is this an Android device?

roberto64 · Jul 17, 2017

Erel · Jul 18, 2017

It is completely different in Android. Please start a new thread in B4A forum.

falbertini · Oct 5, 2017

Hello Erel, could you post wire schema of GPRS Shield to Arduino for the project as in your initial image ? Thanks.

Erel · Oct 8, 2017

You can see a better picture with the connections here: https://www.b4x.com/android/forum/threads/http-requests-with-gsm-shield.81382/

The following pins should be connected between the Arduino and the shield:
- 7, 8 (software serial port).
- GND
- 5v

If you are using Arduino Mega then you need to connect different Arduino pins to the serial port pins.

Shay · Nov 22, 2017

I got the A6 module,
I have this code:

B4X:

Sub MessageArrived(msg() As Byte)
    Log ("Got SMS", msg)
End Sub

when I am getting SMS, I see only gibrish in the logs
I tried changing both Serial baudrate, and GSM serial baud rate
still cannot see any text.
beside appstart, all is gibrish from A6

Shay · Nov 22, 2017

update: I switch between rx and tx pin, now I can see text (weird since it is connected ok),
but I am getting this:
****************
+CIEV: "MESSAGE",1
+CMT: ,29
07917952939899F9040C91795224229BFD06DDDF723619

and I am sending to the a6: "Hello World"

Erel · Nov 23, 2017

Your module is different than the one used in this example (SIM 900).

Arduino example of sending SMS with A6: https://alselectro.wordpress.com/2016/09/14/gsm-a6-with-arduino-making-a-call-sending-sms/

Shay · Nov 24, 2017

How do I put responses to variable so be used?

Erel · Nov 26, 2017

Not sure that I understand the question. However as you are using a different module then it is better to post it in a new thread.

Shay · Nov 26, 2017

Not related to my board, this is general question,
if for example I am getting SMS, how do I manipulate the text, since all is in byte()
meaning putting into var (do I need to use bc.copy?)

Erel · Nov 26, 2017

You should always start a new thread for your questions.

MaurizioRoma · Feb 6, 2018

Hi everybody, I recently purchased a GSM/GPRS shield identical to the one used in the example posted by Erel and uploaded the GSM_Example code. Unfortunately it doesn't work. More specifically, I noticed that in GSM Module, the "busy" variable remains setted to TRUE after the Sub SendCommand is executed, therefore I cannot send any SMS.

I also forced the execution of the sub by commenting the line

B4X:

If busy Then Return False

but, anyway, it doesn't send any SMS.

I tried uploading the source code via the .ino sketch attached and it works properly.

#include <SoftwareSerial.h>

SoftwareSerial SIM900(7, 8);

void setup() {
Serial.begin(115200);
SIM900.begin(19200);

Serial.println("AppStart");
delay(20000);
sendSMS();
}

void loop() {

}

void sendSMS() {

SIM900.print("AT+CMGF=1\r");
delay(100);
SIM900.println("AT + CMGS = \"+xxxxxxxxx\"");
delay(100);
SIM900.println("Hello, how doin'?!!");
delay(100);
SIM900.println((char)26);
delay(100);
SIM900.println();
delay(5000);
}

I also tried to substitute the original code in the Sub EnableSMSEvents with the "AT+CMGF=1" command, and to add the slashes (\) to the phone number, but I failed.
Has anyone an idea of what I've done wrong?

Thanks in advance

Maurizio

Erel · Feb 6, 2018

Please start a new thread for this.

B4R Tutorial GSM / GPRS - Control the Arduino with SMS messages

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