OK...
your signals "seem reasonable"... that is layer-1, lwIP starts at layer-3.
Do you know if your messages actually go out of your hardware ?
Have you tried sniffing with wireshark ?
Above your hardware there is:
Your driver, the layer-2 code, in lwIP terms: "the netif". This has been
written
Depending on where you are, and what you use, you might find the
outdated doc directory inside the main release file and the contrib tree
examples in the contrib release file, enough. That covers 1.4.1
The git repository has its doc files updated, plus some Doxygen
embellishment:
