There are two Ethernet modules which are very popular in the open-source / maker community: Microchip’s ENC28J60, which requires software TCP/IP stack, and Wiznet’s W5500, which has hardware TCP/IP stack. There is no doubt that W5500 is more superior since it frees the microcontroller from having to handle TCP/IP stack. It used to be that W5500 was significantly more expensive, also since OpenSprinkler started with DIY kit, only ENC28J60 has through-hole version so naturally I chose ENC28J60. Since all OS legacy versions also use ENC28J60, it has been a pretty well tested platform. So even though its software TCP/IP stack requirement is a downside, I don’t think this chip itself has any intrinsic problem.
As we moved on to OS 3.0, which has built-in WiFi, it seems customers still want wired Ethernet option, so I again chose ENC28J60 as the module to go with. Prior to firmware 2.1.8, we’ve been using the EtherCard library to handle ENC28J60 — it works pretty well but it’s incompatible with Arduino’s Ethernet library, so that’s a big bummer. From firmware 2.1.8 we’ve started using the UIPEthernet library, which is implemented for ENC28J60 but is fully compatible with Arduino’s Ethernet library. This has the advantage of dramatically simplifying the code, since the same code is cross-compilable for all of OS 2.3, OS 3.0 and OSPi. It hasn’t been long enough since we used UIPEthernet library, so I am not entirely sure about the technical issues. It seems locking up is one potential recurring issue, and I’ve spent the weekend trying to debug and figure out the root cause of it. As John K said, it’s not so easy to debug as there is no fixed access pattern that will trigger this issue. Also when the problem happens, my controller’s symptom is very different from what Wendell observes, that is, everything still seems to be running just fine, the controller responds to button clicks, time is correct, and programs still run, but the controller does not respond to ping test or HTTP requests.
While digging into the issue, I’ve also invested some time looking at W5500 modules. The good thing is that since UIPEthernet is fully compatible with Arduino’s Ethernet library, which is also what W5500 library is compatible with, changing the source code to use W5500 is almost just a matter of switching the header file. The only tricky thing is that these off-the-shelf W5500 modules have a different pin layout than ENC28j60, so I designed a small adapter that can convert the pin layout between the two. I am still waiting for the adapter PCBs to arrive. I have high hopes that W5500 should completely eliminate the lockup issue, and with the pin adapter it can easily replace your existing ENC28J60 module.
So in short summary, I am debugging UIPEthernet library for ENC28J60 but at the same time also getting prepared to transition to W5500.