The default W5500 build:

WIZNET=1 RELEASE=1 BOARD=ESPRUINOBOARD make
...
bash scripts/check_size.sh espruino_1v95.1392_espruino_1r3.bin
FAIL - size of 231460 is over 231424 bytes

The new W5100 build:

WIZNET=1 W5100=1 RELEASE=1 BOARD=ESPRUINOBOARD make
...
bash scripts/check_size.sh espruino_1v95.1392_espruino_1r3.bin
FAIL - size of 231884 is over 231424 bytes```

Please note that this PR is so far just blind software only work without any HW testing done.

That's very cool - thanks! I'll try and give this a go on some actual hardware when I get a chance.

It's always been really tight trying to get everything to fit in the original board, so I'm not super surprised about this - but I wonder what got added to the driver that bulked it out so much :(

Not having much luck here either. It looks like ctlwizchip(CW_GET_PHYLINK doesn't work for W5100 so can be commented out, but even after that I'm not able to set/get the IP with:

eth.setIP({
ip:"192.168.1.123",
subnet:"255.255.255.0",
gateway:"192.168.1.1",
dns:"8.8.8.8",
mac:"00:08:dc:ab:cd:ef"});
eth.getIP();

This should just be a matter of writing to SPI registers, so I'm not sure what's up. It might even be electrical since the shield is meant for 5v inputs... I wonder if it works so well off 3.3v data lines.

It works! It was because the shield I used actually had SPI on the tiny little header at the end - not on D11,12,13 like I was expecting.

All merged in - thanks!