STM_IoT_1: Reading MAC address of the WiFi

Each network card is supposed to have a unique physical address called a MAC address. MAC abbreviation stands for Medium Access Control protocol, which provides access to the physical link in the network layer. The STM32WB55 SoC doesn't have a WiFi network controller so our STM laboratory stands have the WiFi module based on ESP32-C3 SoC connected by serial port additional ESP32-C3 module and controlled with AT commands. To learn how to use these commands please refer to the STM_IoT_Intro chapter.
ESP32 chip has built-in MAC. MAC can be used to identify devices, but note that it is not a “strong” ID: it can be programmatically changed and easily discovered. In the following scenario, we present how to read and display the MAC address on LCD. Displaying on other display than LCD is up to the developer. You can refer to the appropriate scenario, as listed below.

To implement this scenario, it is necessary to get familiar with at least one of the following scenarios first:

• STM_IoT_AT: Programming of the WiFi interface with AT commands,
• STM_5: Using LCD Display,
• STM_6: Using ePaper display,
• STM_7: Using OLED display.

• C/C++ Language Embedded Programming Fundamentals,
• STM32,
• ESP32 General Information,
• SUT STM32 Laboratory Node Hardware Reference,
• Networking for Espressif.

Present a MAC address on the selected display. The steps below present the reading part and display it on LCD. This display has 16 characters per line, but the commonly used format for MAC addresses requires 17 characters. For seeing the full MAC address modify the example and use the display other than LCD.

Check if you can see a full LCD in your video stream. Book a device and create a dummy Arduino file with void setup()… and void loop()….

Include the LCD library in your source code:

#include "LiquidCrystal.h"

Create objects of the LCD and Hardware Serial classes:

// Serial port class and configuration (Constructor uses STM port numbering)
HardwareSerial WiFiSerial(RxD_PIN, TxD_PIN, NC, NC);
 
// LCD class
const int rs = PC5, en = PB11, d4 = PB12, d5 = PB13, d6 = PB14, d7 = PB15;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

Declare two variables with the strings to be compared with the responses from the WiFi module.

String compOK;
String compERROR;

In the Setup() function initialise the serial port, display, and strings.

WiFiSerial.begin(115200);
lcd.begin(16, 2);
compOK = "OK";
compERROR = "ERROR";

We will use the code template from STM_IoT_AT: Programming of the WiFi interface with AT commands to communicate with the WiFi module. The first command we will send “AT” to confirm that everything works properly:

WiFiSerial.println("AT");
lcd.setCursor(0,0);
lcd.print("AT              ");
do {
  response = WiFiSerial.readStringUntil(0x0A);
  lcd.setCursor(0,1);
  lcd.print(response);
} while (!(response.startsWith(compOK)));
 
delay(1000);

The next command can be the “AT+CIPSTAMAC?” which returns the MAC address in the response message which looks like this:

+CIPSTAMAC:"84:fc:e6:88:63:d1"

We can implement the part of displaying the MAC by repeating the block of the code similar to the one presented above with two modifications. Change the “AT” command, and add inside the code the following lines:

if (response.startsWith("+CIPSTAMAC")) {
  response.remove(0,12);
  lcd.setCursor(0,0);
  lcd.print(response);
}

You should be able to see the MAC address of the ESP32-C3 module.

Can I change MAC?: Actually, yes, you can. It is not advised, however, because you may accidentally generate an overlapping address that will collide with another device in the same network.

Project information

This Intellectual Output was implemented under the Erasmus+ KA2.
Project IOT-OPEN.EU Reloaded – Education-based strengthening of the European universities, companies and labour force in the global IoT market.
Project number: 2022-1-PL01-KA220-HED-000085090.

Erasmus+ Disclaimer
This project has been funded with support from the European Commission.
This publication reflects the views of only the author, and the Commission cannot be held responsible for any use that may be made of the information contained therein.

Copyright Notice
This content was created by the IOT-OPEN.EU Reloaded consortium, 2022,2024.
The content is Copyrighted and distributed under CC BY-NC Creative Commons Licence, free for Non-Commercial use.