Reading responses from Serial not working

Projects Programming
1

Hi guys, I'm working on a project where I send some AT commands, and I want to send a new commands only after recieving the "OK", so I made this function where the at commands are the inputs:

int WaitResp(const char* a){

String incomingByte="";   // for incoming Serial data
int len=0;
int i=0;

Serial.flush();
delay(1000);
Serial.write(a);
 
delay(300);
        
               if(Serial.available()>0) {
                // read the incoming byte:
                incomingByte = Serial.readString();// read the incoming data as string
                // say what you got:
                
                
                len = incomingByte.length();
                char reso[len]={};
                incomingByte.toCharArray(reso, 50);
                i=len;
               
                         
                if(reso[len-3]=='K')
                return 1;
                else {
                return 0;
                }
        }    
}

it worked only for the first commands, when I did a small loop to see what's happening

for(i=len;i>1;i=i-1){

            Serial.print(reso[len-i]);
          }

it show this :

AT
AT
OK
AT+CGNSTST=0
AT
OK

OK
AT+CGNSTST=0
OK

And it's stop like this, even tho there're more commands to come.

can anyone help me to resolve this please?

NB: I'm using a hardware serial.

2 
String incomingByte="";   // for incoming Serial data

That is a horrendously stupid name. A byte is NOT a String.

                len = incomingByte.length();
                char reso[len]={};
                incomingByte.toCharArray(reso, 50);

The second argument to the toCharArray() method is the size of the array to write to, not some number you pulled out of your ass.

3

Post complete code. The above output is not from the posted code. Don't use the String class, use C-style strings (null byte terminated character arrays).

Are you sure that your communication partner is always able to respond to your command within 300ms?