Sending strings between functions

Using Arduino Programming Questions
1

Hi guys!
I'm trying to make a program, where an incoming Hexadecimal value gets converted into a normal string.

I was trying to use a function for this, since I think I want the conversion to run only once. If I were to put it into the void loop(), then it would spam the serial monitor.

Here is the code:

  String asciiString;
  String hexString;


void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Serial2.begin(115200);
  delay(1000);
}

void hextostr() {
  Serial.println(hexString);

  for (uint8_t i = 0; i < hexString.length(); i += 2) {
    String hexChar = hexString.substring(i, i+2);
    char c = (char) strtol(hexChar.c_str(), NULL, 16);
    asciiString += c;
    }
  Serial.println(asciiString);
}

void loop() {
  // put your main code here, to run repeatedly:
  while (Serial.available()) {
    String data = Serial.readString();
    Serial2.println(data);
  }

  while (Serial2.available()) {
    String data = Serial2.readString();
    Serial.println(data);
    String hexString = data;

    hextostr();
  }
}

Right now, I get the received hexadecimal perfectly, and I can print it out, but for some reason, the global variable "hexString" doesn't carry it's string over to my function, and I get nothing for the translated string.

(I should add, that the translation process works perfectly fine in a separate program, I can translate any hexadecimal string to a normal string. Here is the code for that one:

void setup() {
  Serial.begin(9600);
  String hexString = "7465737a7465737a7465737a7465737a743132333132333b3b3b2e2e2d2d"; // your hexadecimal string
  String asciiString = "";
  for (uint8_t i = 0; i < hexString.length(); i += 2) {
    String hexChar = hexString.substring(i, i+2);
    char c = (char) strtol(hexChar.c_str(), NULL, 16);
    asciiString += c;
  }
  Serial.println(asciiString);
}

void loop() {}

)

Any help would be appreciated!

2

you cold use sscanf(), e.g.

 String asciiString;
String hexString = "7465737a7465737a7465737a7465737a743132333132333b3b3b2e2e2d2d"; // your hexadecimal string
 


void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial2.begin(115200);
  delay(1000);
  hextostr() ;
}

void hextostr() {
  Serial.println(hexString);
  for (uint8_t i = 0; i < hexString.length(); i += 2) {
    char c;
    sscanf(&hexString.c_str()[i], "%2x",  &c);
    asciiString += c;
    }
  Serial.println(asciiString);
}

void loop() {}

a run gives

7465737a7465737a7465737a7465737a743132333132333b3b3b2e2e2d2d
teszteszteszteszt123123;;;..--

what microcontroller are you using?

3

managed to solve the issue in the meantime, the problem was that the LoRa module I was using inserted a "radio rx " string before the actual data, so I had to get rid of that using string.Remove, and now its working.

However, I get this weird phantom character at the end of every translated sentence.

The fixed code:

  String asciiString = "";
  String hexString = "";
  char c = "";
  String data;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Serial2.begin(115200);
  delay(1000);
}

void loop() {
  // put your main code here, to run repeatedly:
  asciiString = "";
  hexString = "";
  char c = "";
  while (Serial.available()) {
    String data = Serial.readString();
    Serial2.println(data);
  }

  while (Serial2.available()) {
    String data = Serial2.readString();
    Serial.println(data);
    hexString = data;
    hexString.remove(0, 9);
    hextostr();
  }
}

void hextostr() {
  Serial.println(hexString);

  for (uint8_t i = 0; i < hexString.length(); i += 2) {
    String hexChar = hexString.substring(i, i+2);
    char c = (char) strtol(hexChar.c_str(), NULL, 16);
    asciiString += c;
    }
  Serial.println("Incoming Message:");
  Serial.println(asciiString);
}

The answer it gives to 737a6961:
"szia☐"

as if when you have a wrong baud rate selected

I have no idea where that box icon comes from.
4

could be due to the : on the end of the hex string 737a6961:

5

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