Find OK or ERROR in serial string

Question

I am trying to figure out how to capture the OK or the ERROR from a SIM800l.

I have tried

mySerial.println("AT");
while (mySerial.available() > 0 ) {
String str = mySerial.readString();
Serial.println(str);
 if (str.equals("OK")) {
 Serial.println("ok");
 } else {
 Serial.println("unknown");
 }
 }

But I always getting nothing back?

• StarCat: Does this answer your question? Comparing a String after reading it from Serial fails. The issue is that the string read from the serial port also contains a closing "newline" character so the comparison fails. You need to strip off the newline.

Answer 1

You can use .indexOf to find characters in a String. It returns a -1 if a match is not found. See https://www.arduino.cc/reference/en/language/variables/data-types/string/functions/indexof/

mySerial.println("AT");
String str;
while (mySerial.available() > 0 ) 
{
 str = mySerial.readString();
 Serial.println(str);
 if (str.indexOf("OK") != -1) 
 {
 Serial.println("ok");
 } else if (str.indexOf("ERROR") != -1) 
 {
 Serial.println("error!");
 } else {
 Serial.println("unknown");
 }
}