I want to write a function for my arduino project, but I have some issues.
char telephone_number = 111232113;
Serial.println("AT+CMGS=\"telephone_number\"\r");
Console is showing me AT+CMGS="telephone_number" but instead of this I want AT+CMGS="111232113" to be shown.
Is it even possible in this form? I'm new in programming and I don't know how to manage that.
Don't use String. Temptingly easy to use, but you will eventually be sorry. :-( They are slower, use more RAM, and add 1.6k to your program size. Just stick with plain old C strings, also known as char arrays.
You can break your print statement up into three parts:
char telephone_number[] = "111232113";
Serial.print( "AT+CMGS=\"" );
Serial.print( telephone_number );
Serial.println( "\"\r" );
You can save even more RAM space by using the F macro around the print of double-quoted strings:
char telephone_number[] = "111232113";
Serial.print( F("AT+CMGS=\"") ); // Saves 10 bytes of RAM
Serial.print( telephone_number );
Serial.println( F("\"\r") ); // Saves 3 bytes of RAM
Any place you print a double-quoted string like that, just wrap it with the F macro.
BTW, I assume the telephone number(s) is not a constant, so you need to keep it in RAM, as the char array shown here.
You were almost there!
There are two points you need to fix:
char telephone_number = 111232113;. The type char is usually used to keep a single character. In Arduino, you can to use the class String to represent multiple characters.
In order to concatenate the value of a string variable with another string you need to use the operator +. See String Addition Operator.
Here is the corrected code:
String telephone_number = "111232113";
Serial.println("AT+CMGS=\"" + telephone_number + "\"\r");
