Is it possible to convert MAC address to a string?

Using Arduino Programming Questions
#1

Like the title says.

What my code does: it looks up temperature from a sensor and displays it on my webserver, also every hour it sends the temperature to the database. Pretty simple. But I would like to send my sensor's MAC address as well. I don't care if it's format is XX:XX:XX:XX:XX:XX:XX:XX or like below, I'd just like it to send it. PS! I didn't copy-paste all of the code. Don't yell at me for asking such a simple question, I'm still a beginner :confused: 

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature DS18B20(&oneWire);
char temperatureCString[6];
DeviceAddress tempSensor = {0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX};

const char *ssid = "XXXXXX";
const char *password = "XXXXXX";

long interval = 3600000;
long previousMillis = 0;

WiFiClient client; 
MySQL_Connection conn((Client *)&client); 

char INSERT_SQL[] = "USE temperature; INSERT INTO temperature(temperature, time, date, MAC) VALUES (%s, CURRENT_TIME, CURRENT_DATE, ??)";  //Have to change ??
char query[128]; 


ESP8266WebServer server ( 80 );

IPAddress server_addr(XXX.XXX.XXX.XXX);    
char user2[] = "XXXX";                                       
char password2[] = "XXXXX";                             

void setup ( void ) {
  DS18B20.begin();
    Serial.begin ( 115200 );
    WiFi.begin ( ssid, password );
    Serial.println ( "" );

    // Wait for connection
    while ( WiFi.status() != WL_CONNECTED ) {
        delay ( 500 );
        Serial.print ( "." );
    }
  Serial.println ( "" );
  Serial.print ( "Connected to " );
  Serial.println ( ssid );
  Serial.print ( "IP address: " );
  Serial.println ( WiFi.localIP() );

  Serial.println("Connecting to database"); 

   while (conn.connect(server_addr, 3306, user2, password2) != true) { //Connect to database
     delay(200); 
     Serial.print ( "." ); 
   } 

  Serial.println(""); 
  Serial.println("Connected to SQL Server!");   

    if ( MDNS.begin ( "esp8266" ) ) {
        Serial.println ( "MDNS responder started" );
    }
}

void loop ( void ) {
    server.handleClient();
  long currentMillis = millis();
  if (currentMillis - previousMillis > interval) { //Timer
      while (conn.connect(server_addr, 3306, user2, password2) != true) { 
        delay(200);
      } 
      sprintf(query, INSERT_SQL, temperatureCString, ??); // Have to change ??
      MySQL_Cursor *cur_mem = new MySQL_Cursor(&conn); 
      cur_mem->execute(query); 
      delete cur_mem;                  
      previousMillis = currentMillis;
  }
  getTemperature();
#2

if you have a look at https://www.arduino.cc/en/Reference/WiFi

there is a method WiFi.macAddress() https://www.arduino.cc/en/Reference/WiFiMACAddress

#3

What format are they in now?

Use itoa or ltoa to covert numbers into an ASCII char array.

You can concatenate arrays or on a character by character basis append them to a String.

If you don't mind unsolicited advice, stick to the character array, avoid String unless you absolutely need it.

#4

But I would like to send my sensor's MAC address as well.

Sensors do NOT have MAC addresses.

#5

I don't need to print MAC address, I need to send it to the database.

horace: if you have a look at https://www.arduino.cc/en/Reference/WiFi

there is a method WiFi.macAddress() https://www.arduino.cc/en/Reference/WiFiMACAddress

I can't convert with itoa, because: invalid conversion from 'char*' to 'int' [-fpermissive]

DKWatson: What format are they in now?

Use itoa or ltoa to covert numbers into an ASCII char array.

You can concatenate arrays or on a character by character basis append them to a String.

If you don't mind unsolicited advice, stick to the character array, avoid String unless you absolutely need it.

#6

So that says that they're already ASCII characters. Are they character arrays or strings?

If arrays, concat.

If strings, build a bigger string by appending all the little bits.

Ultimately, for serial transmission the data goes out byte by byte so character arrays are always better.

#7

are you looking to do something along the lines of this code which scans for DS18S20 devices and converts the device byte addr[8] to a char array

// DS18S20 Temperature chip - scan for address 
#include 
OneWire  ds(2);  // on pin 2

void setup(void) {
  Serial.begin(115200);
  delay(1000);
  ds.reset();
  byte addr[8];
  while(ds.search(addr)) {
    char address[30]={0};
    Serial.print("R=");
    for(int i = 0; i < 8; i++) {
      Serial.print(addr[i], HEX);
      // address next part of address
      itoa(addr[i], &address[strlen(address)], 16);
      if(i<7)address[strlen(address)]=':';
      Serial.print(" ");
     }
    Serial.print("\naddress ");   // print address
    Serial.println(address);
    }
  }
void loop(void) {
 }

a run gives

R=28 FF FC 2A 85 16 5 8A
address 28:ff:fc:2a:85:16:5:8a