MAC addresses

Both the Ethernet Shield and the Ethernet Board comes with a unique MAC address printed on a sticker. Is this the only place it is or is it also present in the W5100 chip? If so, how can I get it in code? Or do I really have to manually type it into my sketch file? The Ethernet.begin takes at minimum the MAC address as input.

The latter is very inconvenient as I plan on using several Arduinos on the same network.

Thanks,

Jens.

You could have a temporary sketch write the MAC address into EEPROM and have your final sketch read the value from EEPROM. That way the MAC would follow the Arduino processor.

There is no way for the W5100 to store the MAC address permanently.

Most systems would incorporate a small SPI or I²C EEPROM chip to store the MAC address on the board. Of course, the Arduino has its own EEPROM built in, so you can use that.

I guess the printed MAC address may be there for you to use as a guideline should you wish to.

Thanks for your answers. I will write some utility to take care of this and get it stored in the EEPROM

Jens.

majenko: I guess the printed MAC address may be there for you to use as a guideline should you wish to.

The MAC is supposed to be "Globally Unique" so you can put any two Ethernet devices on the same Ethernet segment and expect them to work together. At a minimum the MAC must be "Locally Unique" in that no two devices on the same Ethernet segment can have the same MAC address.

The printed labels are Globally Unique. If you use any other numbers you take your chances.

DO NOT USE the numbers you find in Ethernet examples. :)