Simple Arduino CRC32 calculator

crc.ino

void setup() {
  Serial.begin(9600);
}

void loop() {
  while (Serial.available() == 0) {
  	String text = Serial.readString();
    
    if (text.length() > 0) {
      unsigned long crc = crc32(text);
      
      Serial.write("CRC32 '");
      Serial.print(text);
      Serial.write("': ");
      Serial.println(crc, HEX);
    }
  }
}

unsigned long crc32(String input) {
 
  const unsigned long divisor = 0xEDB88320;
  unsigned long crc = 0xFFFFFFFF;
  
  for (int i = 0; i < input.length(); i++) {
    crc = crc ^ input[i];
  	
    for (int j = 0; j < 8; j++) {
      bool odd = (crc & 1) == 1;
      crc >>= 1;

      if (odd)
        crc ^= divisor;
    }
  }
  
  return crc ^ 0xFFFFFFFF;
}