You need to post all of your code.
Ok, I first detect if serial is available, if is I put the value into int and then i convert it to string. I first was trying to convert it to text with things like this
vstup = String(input, DEC);., but it didn't helped
int input =Serial.read();
vstup = String(input); //vstup = Czech word for input
odpovez(vstup); //call custom function and input converted to string as parameter
And then in my custom function is part like
if ( input == 116) //if I send "t"
Rest of code is to read values from sensors and send them via serial port and it is made in Czech language.
I hope it should be enought of code