This Ethernet module turned out well actually, but I must admit that the need to move to 0402 or even 0201 componenrs is pressing on.
Firmware download is a bit of a concern that I need to work on – it is specially two download sequences that is of interest:
1 – Download of new Ethernet FW.
2 – Download of new Main FW.
These two have the potential to fail and leave us with a dead box, so they need special attention. Main can load FW to any module directly, but if the new FW for Ethernet is broken or a new main FW is broken we risk ending up with a dead box that can’t be upgraded without a SWD. The answer is that I need to implement fail-safe options on Main. Main bootloader must reset to previous image and Main module loader must do the same.
Build In Bootloaders are great, but I fear we need a specialized one for the main board to be secure.