PoE MicroMod Ethernet Function Board - how to get hardware MAC address?

Development Boards MicroMod
1

Hi there,

as I cannot find anything about it in the hookup guide or in the INO examples - has the named board a unique hardware MAC address and if so, how can I retrieve it in the sketch?

In the provided example, the MAC address is defined in the sketch. This won’t work if I use several of those devices on the same network.

If the board has no unique hardware mac address, I thought about using a random mac address generator, but that of course has its own limitations (need to store generated address in EEPROM for using DHCP IP/MAC assignment). Is there a better solution for this?

Thanks,

Michael

2

Hi Michael,

The W5500 has no pre-defined MAC address. You do need to generate one externally and write it to the W5500 SHAR register. You will unfortunately need to store the address in your microcontroller code / memory.

Previously, I’ve used random valid addresses generated by the website linked below, and stored them in microcontroller flash (“EEPROM”) memory.

I hope this helps,
Paul

3

THanks @PaulZC

Unfortunately as I found out meanwhile, it looks like the ESP32 Micromod Processor does not have an EEPROM that I could use to store a generated MAC address persistently.

I did not find anything about EEPROM when using the Micromod Single board along with the ESP32 processor.

Or do I miss something here?

4

Arduino ESP32 supports EEPROM. Please see the link below.

But, we tend to use LittleFS (Little File System) not EEPROM. You do need to make sure you have defined a flash memory partition for LittleFS / “spiffs”. That’s usually available as standard, but it does depend on your Board definitions. Link below.

5

Thanks again @PaulZC

Meanwhile I found another solution: the ESP32 has a globally unique 48-bit serial number stored as uint64_t.

It can be retreived with ESP.getEfuseMac() and then converted to a unique MAC address:

uint8_t mac[6] = {0x00,0x01,0x02,0x03,0x04,0x05};

void CreateMacAddress()

{

uint64_t chipid = ESP.getEfuseMac(); // 48-bit MAC

mac[0] = (chipid >> 40) & 0xFF;

mac[1] = (chipid >> 32) & 0xFF;

mac[2] = (chipid >> 24) & 0xFF;

mac[3] = (chipid >> 16) & 0xFF;

mac[4] = (chipid >> 8)  & 0xFF;

mac[5] =  chipid        & 0xFF;

}
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6

Nice… I’m stealing that! :laughing:

Best wishes,
Paul

7

esp_read_mac should work well for you. The convention is to take the Base (WiFi) Address and add 3 to the last octet for Ethernet.

esp_read_mac(yourAddress, 3) does it all in one call…

Links below…

Best wishes,
Paul

https://espressif-docs.readthedocs-hosted.com/projects/esp-idf/en/stable/api-reference/system/system.html#mac-address

https://espressif-docs.readthedocs-hosted.com/projects/esp-idf/en/stable/api-reference/system/system.html#_CPPv412esp_read_macP7uint8_t14esp_mac_type_t

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