I have completed testing of 3 firmware versions. The first firmware is one that I compiled
and has debugging code that would provide the state of the IP stack if a hang happened.
The second 2 firmware versions, OS220(90).bin and OS220(91).bin, are from the previous post.
I ran each for 1 week in my normal setup. This is just the OS 3.2 sitting on my desk with
only power, the RS232, and the ENC28J60 connected. I have no zone valves connected. I
have a web browser pointed at the OS. This setup would usually produce a hang within
one week.
The result is that all 3 firmware versions ran the full week with no problems.
It seems that the problem is solved by using the latest version of UIPEthernet 2.0.9.