SIM800l GSM.reset() problem

Projects Networking, Protocols, and Devices
1

Hi, I'm building an SMS Alarm for the refrigerator in my biochemistry lab.
I'm using a SIM800L, the one that can be supplied directly with 5V.

I'm facing some issue with the SIM800L library I'm using.
The GSM.reset() function is not working properly, the Arduino gets stuck waiting for a response message from the GSM module.

This is the reset() code from the library:

void Sim800L::reset()
{
    if (LED_FLAG) digitalWrite(LED_PIN,1);

    digitalWrite(RESET_PIN,1);
    delay(1000);
    digitalWrite(RESET_PIN,0);
    delay(1000);
    // wait for the module response

    this->SoftwareSerial::print(F("AT\r\n"));
    while (_readSerial().indexOf("OK")==-1 )
    {
        this->SoftwareSerial::print(F("AT\r\n"));
    }

    //wait for sms ready
    while (_readSerial().indexOf("SMS")==-1 );

    if (LED_FLAG) digitalWrite(LED_PIN,0);

}

I did some experimenting with direct AT communication with the module. I noticed that the module it's not always responding "SMS ready" to the first "AT" message, even though it's registered to the network and it's capable to send SMS.

So I tried to remove the second to last line of the code from the library but Arduino still gets stuck waiting for a response from the module. To make it work properly I had to remove also the part of the code in which Arduino waits for the OK message.
Why I'm facing this communication problem and what can I do to fix it?

GSM alert_bb.png
GSM alert_bb.png1335×1233 152 KB

2

Solved: The problem was about the software serial communication and the auto baud rate of the module.
I fixed the Module Baud Rate at 9600 and this solved all my problems.

AT+IPR=9600 //set the baud rate at the desired value
AT&W //Save the current setting

Now, every time it boots up I can read

RDY

+CFUN: 1

+CPIN: READY

Call Ready

SMS Ready