Compilation error: 'dump_byte_array' was not declared in this scope

Other Hardware Sensors
1

I want to create a game where people have to put the right objects in the right place, in order for a door to open. To get the job the done, I thought of doing it with RFID sensors and found this code(exacly what I need).

The problem is that I cant upload it due to this error: "Compilation error: 'dump_byte_array' was not declared in this scope"

I have no idea how to solve it, can anybody help me?

#define DEBUG
// LIBRARIES
#include <SPI.h>
#include <MFRC522.h>
// GLOBALS
// The number of RFID readers
const byte numReaders = 3;
// Each reader has a unique Slave Select pin
const byte ssPins[] = {2, 3, 4};
// They'll share the same reset pin
const byte resetPin = 8;
// Initialise an array of MFRC522 instances representing each reader
MFRC522 mfrc522 [numReaders];
// The sequence of NFC tag IDs required to solve the puzzle
const String correctIDs[] = {"3acbbd49", "ca767564", "3af4f763", "87e0f0a4"}; 
// The tag IDs currently detected by each reader
String currentIDs [numReaders];
// This pin will be driven LOW to release a lock when puzzle is solved 
const byte lockPin = A0;
/**
* Initialisation
*/
void setup() {
  #ifdef DEBUG
  // Initialise serial communications channel with the PC 
  Serial.begin(9600);
  Serial.println (F("Serial communication started")); 
  #endif
  // Set the lock pin as output and secure the lock 
  pinMode(lockPin, OUTPUT);
  digitalWrite(lockPin, HIGH);
  // Initialise the SPI bus
  SPI.begin();
  for (uint8_t i=0; i<numReaders; i++) {
    // Initialise the reader
    // Note that SPI pins on the reader must always be connected to certain 
    // Arduino pins (on an Uno, MOSI=> pin11, MISO=> pin12, SCK=>pin13) 
    // The Slave Select (SS) pin and reset pin can be assigned to any pin 
    mfrc522[i].PCD_Init(ssPins[i],resetPin);
    // Set the gain to max - not sure this makes any difference..
    //mfrc522[i].PCD_SetAntennaGain (MFRC522:: PCD_RxGain::RxGain_max);
    // Dump some debug information to the serial monitor
    Serial.print(F("Reader #"));
    Serial.print(i);
    Serial.print(F(" initialised on pin "));
    Serial.print(String (ssPins[i]));
    Serial.print(F(". Antenna strength: "));
    Serial.print(mfrc522[i].PCD_GetAntennaGain ()); 
    Serial.print(F(". Version : "));
    mfrc522[i].PCD_DumpVersionToSerial();
    // slight delay before activating next reader 
    delay(100);
  }
  Serial.println (F("--- END SETUP ---"));
}

void loop() {
  // Assume that the puzzle has been solved
  boolean puzzleSolved = true;

  // Assume that the tags have not changed since last reading 
  boolean changedValue = false;
  
  // Loop through each reader
  for (uint8_t i=0; i<numReaders; i++) {
    // Initialise the sensor
    mfrc522[i].PCD_Init();
    // String to hold the ID detected by each sensor 
    String readRFID = "";

    // If the sensor detects a tag and is able to read it
    if (mfrc522[i].PICC_IsNewCardPresent() && mfrc522[i].PICC_ReadCardSerial()) { 
      // Extract the ID from the tag
      readRFID = dump_byte_array(mfrc522[i].uid.uidByte, mfrc522[i].uid.size);
    }
    
    // If the current reading is different from the last known reading 
    if (readRFID != currentIDs [i]) {
      // Set the flag to show that the puzzle state has changed
      changedValue = true;
      
      // Update the stored value for this sensor
      currentIDs[i] = readRFID;
    }

    // If the reading fails to match the correct ID for this sensor
    if (currentIDs[i] = correctIDs[i]) {
      // The puzzle has not been solved
      puzzleSolved = false;
    }

    // Halt PICC
    mfrc522[i].PICC_HaltA();
    // Stop encryption on PCD
    mfrc522[i].PCD_StopCrypto1();
  }

  // If the changedValue flag has been set, at least one sensor has changed 
  if (changedValue) {
    // Dump to serial the current state of all sensors
    for (uint8_t i=0; i<numReaders; i++) {
      Serial.print (F("Reader #"));
      Serial.print (String (i));
      Serial.print (F(" on Pin #")); 
      Serial.print(String ((ssPins[i]))); 
      Serial.print (F(" detected tag: ")); 
      Serial.println (currentIDs[i]);
    }
    Serial.println(F("---"));
  }

  // If the puzzleSolved flag is set, all sensors detected the correct ID 
  if (puzzleSolved){
    onSolve();
  }

  // Add a short delay before next polling sensors 
  //delay(100);
}

void onSolve () {
  #ifdef DEBUG
  // Print debugging message
  Serial.println (F("Puzzle Solved!"));
  #endif

  // Release the lock
  digitalWrite(lockPin, LOW);

  while(true){}
}
2

The library usually has

but here it seems you want to read something out of this function call (void means it returns nothing)...

where did you find that code ?

3

First of all, thank u for the quick response!
I tried to add that and it solved that error but created another: "Compilation error: no match for 'operator=' (operand types are 'String' and 'void')"

I got this code from this video:

4

Unfortunately it does not seem the full source code is readily accessible (needs to go through Patreon - and probably you aren't supposed to share that code freely )

Are you sure there were not other .ino files ? The code as shared is indeed not complete

5

Actually, I think I just found the answer:

String dump_byte_array(byte *buffer, byte bufferSize) {
    String output = "";
    for (byte i = 0; i < bufferSize; i++) {
        output += String(buffer[i], HEX);
    }
    return output;
}
6

Yes probably something like that (not efficient to deal with an ASCII representation but does the job)

7

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