SIM800l + Arduino UNO does not respond

Projects Networking, Protocols, and Devices
1

Hi everybody,

I have a part of my project who is very simple, I would like to send SMS with my Arduino UNO but it's not working >:( .
I explain my problem.

When i push my code to the arduino and type on console BAUD 9600 seems yesterday my MODEM does not respond anymore.

I don't know why and what I have to do.
Yesterday my AT command return me OK but now I can see anything.

When I put an empty code, then I have light blinking on my MODEM but when I put the code it's blinking, and when on console I put AT or other command, it stop blinking and does not respond.

The module
Here

My code

// Connect VCC to +5V
// Connect GND to Ground
// Connect RXD (data into SIM800L) to Digital 8
// Connect TXD (data out from SIM800L) to Digital 7
#include <SoftwareSerial.h>
SoftwareSerial sim800l(7, 8); // RX, TX
String SIM_PIN_CODE = String( "XXXX" );

void setup() {
 Serial.begin(9600);
 sim800l.begin(9600);
 sim800l.print("AT+CPIN=");
 sim800l.println( SIM_PIN_CODE );
}

void loop(){
 if (sim800l.available())
 Serial.write(sim800l.read());

 if (Serial.available()) {
 while(Serial.available()){
 sim800l.write(Serial.read());
 }
 sim800l.println();
 }
}

RX to pin 7 (I try inverted)
TX to pin 8 (I try inverted)
GND to GND
5V to LN4007 to 5V

Did you have any idea with my problem.

On my code I try with the AT+CPIN=PIN nothing on my console respond, without AT+CPIN too.

Best regards
MVA93

2

After you've written AT command you have to send carriage return character which is "\r" (without quotes) and then newline character which is "\n" (without quotes). Try that.

3

Hello mihajlo2003,

On the console i'm on "both, NL et CR" "9600 baud".
But I will try tonight to type
at
\r
\n
or
at\r\n

I'll give you the return of it.

Thanks for your message

4

But type AT commands in upper case letters.

5

Yes both it's recornized.
I have a trace of my modem when it was working and at or AT was working perfectly.

Yesterday i try even the command at+cipshut and AT+CIPSHUT | atz or ATZ..... not working.

It's not a problem to read the manuel for me :).
And I search to internet, arduino forum i can't find anything about my problem.

All that I found is about the Voltage...

6

If you type it on serial monitor, you don't have to type \r\n because serial monitor does it for you. But, you have to type it in your arduino sketch because arduino doesn't do it for you.

7

Yep is that i was thinking about the begin of my research and you confirm that thanks for the information.
Now i know why I don't send any sms when the GSM module was OK.

So I think we are on the same problem again.
Yesterday night when I was trying my module.

With blank sketch my GSM module is blinking in continue but when I put the code, it blink 3 times and goes down.

That say that the GSM module reboot.
I don't know the reason.

My wire are maybe not connected as well.

7 to RX
8 to TX
GND to GND
5V to LN4007 and 5V

When i start the project my wire was :

7 to RX
8 to TX
GND to GND
5V to 5V

but it was blinking 3 times and rebooting all the time because I was sendng to high voltage on the module.

module is about 3.7~4.2V so I put a capacitor and it was working for 7 days. Now nothing.
Maybe my capacitor ?

8

Capacitor shouldn't affect it, it smooths voltage so it should be even better with it. Do you reduce voltage from 5 volts to 3.7-4.2 volts? 5 volts kills it! I have same module but mine doesn't even connect to network! I have topic on forum: SIM800L can't connect to network - Networking, Protocols, and Devices - Arduino Forum
No one had replied yet.

9

5V dosn't killing it because at my first try i was on 5V but they say that if you're on 5V your modem will make a restart loop because when the module receive 5V he restart.
So yes he affect the module if you let at 5V for a long time. I try 1 night on 5V and after I put the LN4007 capacitor and console was working good.

AT respond OK

AR+CPIN=1234 respond
CPIN=READY
CALL READY
SMS REDAY

After I would have other problem that my sim card was always not recornized.
The next day i connect for tying again and boom nothing more on console.

10

Try reading this: http://www.ayomaonline.com/programming/quickstart-sim800-sim800l-with-arduino/
They say that voltage should always be 3.7-4.2 volts and never 5 volts.

11

When i connect my modem on 5V I reading this to understand why

https://forum.arduino.cc/index.php?topic=359213.15

And after it was working.
Now not you think that the voltage was causing that problem ?

12

Maybe.