A little while back, I was musing upon the desirability of  the new WizNet WIZ820io ethernet breakout board. It’s a magjack and W5200 chip combination that (in theory) allows you to simply add network connectivity to your projects with a few SPI connections and a slightly modified version of the standard Arduino Ethernet library.

At the time I was looking, the only place I could find selling them in the UK was Mouser, but I couldn’t think of 50 quid’s worth of things to throw money at to avoid paying their hefty delivery charges for small purchases. Instead Mike at HobbyTronics ordered a few in and mine arrived with the postman … about an hour before leaving for a holiday. Now that we’re back, unpacked and I’ve finally got a minute to myself I could see if it really was as straightforward as it looked.

There’s a couple of good introductory resources to the board that I found that go into much more detail than I need to here; the WizNet product page itself (from which you can get the user guide and updated Ethernet library files), Ben Robert’s intro from the WizNet blog and here’s a handy Fritzing project you can use as a basis for your own diagrams. With the library updated, hooking up the board is as simple as power, ground, SPI connections and a link to the Arduino’s reset line.

WizNet WIZ820io connected to Arduino Uno

WizNet WIZ820io and Arduino Uno breadboard layout

As you can see, there’s not a lot to it and once you plug in the ethernet cable and load up any of the examples from the Ethernet library, you’re good to go. Here it is running the UDP NTP Example sketch.

Output of running the NTP client on the WIZ820io

The only problem I had with the board was that initially it was firing up, the lights were on, but the sketches were failing to negotiate a DHCP address and even assigning an IP address directly wasn’t working. I checked and re-checked all the wiring. Cursed people who draw wiring diagrams in a single colour and cross the wires over. Checked the wiring again and it was all as it should be. Fearing I might have ended up with a duff unit, I checked the rest of the environment first. My router was showing the initial DHCP requests arriving, but absolutely nothing after that and then the lease expired 60 seconds later. I plugged into different (known good) ports on the switch, but still no joy. It wasn’t until I bypassed the switch and plugged straight in to the router that everything magically sprung into life. Admittedly, it’s a bit old and not the fanciest piece of kit, but everything else I’ve ever plugged into that switch has been happy, but not the WIZ820io, it seems. I replaced it with a new TP-Link Gigabit switch and the WIZ820io worked first time. Now I don’t know if the fundamental problem is with the switch or the ethernet module, but I wanted to mention it in case anybody ever ends up here after spending time trying to fix a similar issue.

The old Gigabyte GS-SW005 switch which didn't work with the WIZ820io
The new TP-LINK TL-SG1005D Gigabit Switch

Whilst I was away on holiday, I see that Nathan Chantrell’s snuck a lead on me and offered up his first impressions of the module – he’s even gone and found someone on eBay selling the modules for less than I paid (there were none on there when I last looked). The module’s also being used for a newly announced ATmega1284P-based board called the Max1284. If you want to see other uses of it, do a Google image search for “wiz820io” – half the results come back from Asian sites, but even if Google Translate misses some of the finer details, you can see a lot of what’s going on from the pictures.

So, in summary; yes the WizNet WIZ820io is a simple plug and go solution for adding ethernet connectivity to your Arduino (or whatever) project, provided you update your library and your network switch isn’t too old. As to its value – compared to a full-blown official shield that’s currently retailing at £33 (and which also gives you an SD card slot), the £25 price being asked by HobbyTronics isn’t especially brilliant. With the module being offered at £20 including postage on eBay, that’s a bit more like it. Mouser appears to be offering them at £15 each, but it wasn’t immediately obvious if that was an ex-VAT price – I suspect it is and you’ll also be paying 12 quid delivery unless you top up the order. Hopefully over the coming months, with more interest more suppliers will stock it and if it stabilised around the £20 mark, I’d say that was a fair price.