Writing MAC Address to EEROM


#1

Hi,

Does anyone know how to write a different MAC address to the EEROM on the IESM expansion card?

The fastrack_ethernet Open AT example code allows other IP addresses to be re-written, but not the MAC address.
In the example code, it looks as though the idea was there for creating a new AT command i.e. AT+MAC, but this was not completed. If anyone out there has code that will allow the MAC to be read and written, I would be most grateful to see it.

Thanks.


#2

Sounds rather dangerous to me!

Isn’t it pretty much essential that MAC addresses are globally unique? In which case, allowing it to be arbitrarily written is not a Good Thing… :open_mouth:


#3

You need to change the MAC if you want to generate your own universally administered address product using Wavecom modules. The first three bytes are “Organizationally Unique Identifier” which identifies the manufacturer or vendor. So, if you have an IEEE asigned code for those bytes, you need to change the MAC.
http://en.wikipedia.org/wiki/MAC_address


#4

Hiya,

In the sample application (in OpenAT 2.30), the MAC address appears to be stored in an I2C EPROM on the IESM board. This is read from the I2C at initialization, and then written back out to the Ethernet chip over SPI.

Have a look in this wavecom document : Improvement on Memory Chip Power Management and Prevention of Memory Data Loss (Reference: WA_DEV_Fastrk_APN_001, available from the Products->Fastrack Supreme->Downloads->Support->Application Note page) for some info on how the example program stores the IESM MAC address.

The MAC address provided (at least on the IESM card I bought here in Oz) belongs to Wavecom - so is probably unique and safe to use out in the real world…

Note also that the newer Microchip Ethernet controllers come with a default, unique MAC address mask programmed. This can be overwritten at initialization. Microchip also sell pre-programmed MAC address EEPROMS.

ciao, Dave


#5

Hi All,

Thanks for your replies. I really appreciate you taking time to answer.

Mike