From saying "print" rather than "printf" I pressume you are running MicroPython on your WIZnet board ?Ideally, I would like to maintain the debug prints and they would just get ignored when USB is not attached.
Your issue prompted me to get my WIZnet W5500-EVB-Pico up and running - And that delivered good news for me, perhaps not such good news for you.
The MicroPython-based Web Server I developed for my Pico W works just as well using the WIZnet after a change in network initialisation. It allows me to view and download files, plus upload new ones. It does this whether tethered to my Pi with a serial connection or powered from a dumb PSU, and that throws out plenty of 'print' diagnostics even though they are going nowhere.
So "works for me" in initial testing, and we can discount 'print' and disconnected USB.
But, after some time, I did encounter some "Not responding" issues though it did then recover. This might be the same issue of Jumbled TCP requests as I am seeing with my Pico W - viewtopic.php?t=365960 - but perhaps not. I will have to investigate that further.
But as to why you are not seeing anything served when USB serial is disconnected I am not sure.
I don't have any delay at the start of my code but it might be worth adding a 'time.sleep()' at the start to ensure the hardware is up and running before it is accessed.
I am running recent MicroPython firmware I built from source myself but I wouldn't have thought that would be an issue if already using MicroPython sourced firmware rather than what WIZnet may have provided.
I also had an issue when I first connected to its REPL, issued 'import network' and it hung solid, had to be power-cycled, but has been fine since. So I can't say it's perfect' but wouldn't say "doesn't work".
How big is your code; if you can zip it up and post it I am happy to give it a go and see how it behaves for me.
Statistics: Posted by hippy — Thu Feb 22, 2024 7:51 pm