Duplicate MAC addresses on W5500 modules?

[SteveSpencer]

Using the 1.26 build, for W5500 EVB boards. I have a W5100S-EVB-PICO, but no W5500-EVB. However, I have some W5500 modules from previous projects, and by using the same connections (SPI0, Int, CSn) I am able to get them to work as I would expect.

However, it seems that at least two of the modules have the same MAC, and I was under the impression that they had individual ones.
These both appear to be 02:74:e3:78:60:9a, which, as you'd expect, is causing some issues.

Now, I also believed that it was possible to manually set the MAC. The sequence I am using is as follows:
import network n = network.WIZNET5K() n.config(mac=b'\x02\x74\x03\x01\x02\x03') n.active(True)

However, this isn't working. When I look at the network traffic, the module is still using the original MAC when sending DHCP packets, and if I do
n.config('mac')
I see the original MAC. I power down the boards between trials, to make sure that neither the PICO or the W5500 is caching anything, and there is no other user code being run before I do my thing - this is being done via Thonny.

As a test, I queried the MAC before setting the NIC active, and I get back a zero MAC, which looks like it has not yet been initialized.
I can see, using the regs() function, that the MAC is zero before I do anything to change it, and if the NIC is not active, that the value is not changed when I use config(). As soon as I make it active, regs() shows me the hard-coded MAC. :(

Does anyone have any suggestions as to how I can work around this? It looks like my request to set the mac is not effective, but according to the code in the 1.26 extmod/network_wiznet5k.c source, it should be doing the right thing, to my untrained eye.
I have a number of the W5500 modules, and if they all exhibit the same behaviour, this would be problematic.

[Lobo-T]

The W5500 does not come with a MAC. The MAC that Micropython uses on the Pico is generated from the unique id of the flash memory IC of the pico. So if you try several W5500 on the same pico you will get the same MAC. But a different pico should generate another.

[SteveSpencer]

Thanks. You're right about the different boards.
I can't remember where I read that the MAC was provided, but it was a while ago, and is clearly incorrect.

I have looked at the network_wiznet5.c code, and have identified the code that sets the MAC, using the MP method mp_hal_get_mac, which then calls mp_hal_generate_laa_mac (except for builds for W models). In there, I see the board id being retrieved, and then "perturbed" to generate a MAC (rp2/mphalport.c)

This makes life easier for me, because I can write some code that will generate the predicted MAC for a given board. This will allow me to reserve IP addresses in my DHCP server (dnsmasq) without connecting the board to the network and being assigned a random IP from the DHCP pool first.
(My setup has a limited DHCP pool, but determining which IP is which machine is problematic with 1.26 as hostnames set via network.hostname are not sent as part of a DHCP request (although there is a PR from Wiznet to add support for W6xxx series which should contain a fix for this including W5xxx series too).