Switch on an LED via SMS

Using Arduino Programming Questions
1

Hi everyone,

my project is to send a SMS to the SIM800L module which is connected with an Arduino Nano. The Nano should compare the SMS to a saved phone number and if the SMS is from the number it should switch on an LED.

I have achieved, that i can see the SMS in the Serial Monitor, when in the void loop only is updateSerial.

Can someone pls help me, because i don´t get it, where my mistake is.

#include <SoftwareSerial.h>
#include <String.h>

#define PIN_TX 8
#define PIN_RX 9

SoftwareSerial mySerial(PIN_RX, PIN_TX);

int LED = 5;                        //Set Led to Pin 5
char num_1 = "+491525342xxx";      //String with first mobilenumber
String textSms;                     //String to store text

void setup()
{
  pinMode (LED, OUTPUT);            //Set Pin 5 as Output
  digitalWrite (LED, LOW);
  
  Serial.begin(38400);              //Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  mySerial.begin(38400);            //Begin serial communication with Arduino and SIM800L
  delay (1000);

  Serial.println("Initializing...");

  // Once the handshake test is successful, it will back to OK
  mySerial.println("AT");
  delay (1000);
  updateSerial();

  // Configuring TEXT mode
  mySerial.println("AT+CMGF=1");
  delay (1000);
  updateSerial();

  // Decides how newly arrived SMS messages should be handled
  mySerial.println("AT+CNMI=1,2,0,0,0");
  updateSerial();
}

void loop()
{
  updateSerial();
  textSms = Serial.readString();                              //this will save the whole data to the String variable d..                             
  
  if(strcmp(textSms.indexOf("+4915253426039"), num_1) >= 0)  // checking whether the msg(that is saved in d) has got "num_1" in it
   {
   digitalWrite(LED, HIGH);                                  // turning on led
   }
}

void updateSerial()
{
  delay(500);
  while (Serial.available()) 
  {
    mySerial.write(Serial.read());//Forward what Serial received to Software Serial Port
  }
  while(mySerial.available()) 
  {
    Serial.write(mySerial.read());//Forward what Software Serial received to Serial Port
  }
}
2

This won't read the SMS message from the SIM800 because you most likely already read it in the updateSerial routine... that just executed.

3

ok. so how can i then compare the updateserial with the saved number?
or must i work around without the updateSerial?

4

Try this...

char buffer[256];
uint8_t idx = 0;


void loop()
{
  updateSerial();

  if (idx > 0)
  {
    char *ptr = strstr(buffer, "+491525342xxx");

    if (ptr)
      Serial.println("Received SMS from known number");
    else
      Serial.println("Received something else");  

    idx = 0;  
  }
}

void updateSerial()
{

  while (Serial.available()) 
  {
    mySerial.write(Serial.read());//Forward what Serial received to Software Serial Port
  }
  
  while(mySerial.available()) 
  {
    char c = mySerial.read();    
    Serial.write(c);              //Forward what Software Serial received to Serial Port
    buffer[idx++] = c;
  }
}
5

Thanks a lot. Now i get back that i have recieved it, from a known number.

Initializing...
AT

OK
AT+CMGF=1

OK
Received something else
AT+CNMI=1,2,0,0,0

OK
Received something else

+CMT: "+491525342xxx","","22/05/29,16:16:19+08"
A
Received SMS from known number

Do i have to delete the update serial by the AT commands, because now i get the "Received somthing else" there?

Where does the pointer on ptr goes? that i haven´t figuerd out yet.

6

It's abandoned on the call stack when the loop function executes a return. That is because you declared it local to the loop() function.

7

thanks for the explination

8

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