I had the problem you describe, an ip address which was not the one it should be, usually a different one after each reset, sometimes with parts of the address recognisable as parts of the one I was expecting.

I too tried a different W5100 module, different arduino, different connecting wires. No better.

Then I found the answer, which was to supply the W5100 with 3.3v rather than the 5v I had been using. This fixed the problem completely.

It is very odd that supplying the module with 5v stops it working properly, I can't explain it. It has an onboard AMS117 to convert the supply voltage to the 3.3v the chip needs.

Whatever the reason though, it does fix the problem. I have two W5100 modules and neither will work properly if supplied with 5v. Both work perfectly on 3.3v.

I see the instructions for the Mysensors ethernet gateway show the module supplied with 3.3v so I guess when I thought I knew better I was wrong!

Hope this helps.

@mfalkvidd I tried both and neither worked - the node still failed to start.

My workaround is to add MY_DEBUGDEVICE initialization in hwInit() in MyHwSAMD.cpp , immediately after the initialization of MY_SERIALDEVICE,

i.e. insert these lines after line #76: -

MY_DEBUGDEVICE.begin(MY_BAUD_RATE);
#if defined(MY_GATEWAY_SERIAL)
while (!MY_DEBUGDEVICE) {}
#endif

Of course if the two devices are the same then MY_SERIALDEVICE gets initialized twice, but doesn't seem to cause a problem.

fac13 about 2 hours ago

I realized I should have added a wait after the initialization, like this: -

void preHwInit()
{
MY_DEBUGDEVICE.begin(115200);
while(!MY_DEBUGDEVICE){};
}

With that included, my sketch works without needing the architecture code mod.

Putting the same code in before() doesn't work.

Thanks for your help.