I have used my recent W5500 breadboard friendly PCB to overcome problem with W5500 directly on gateway. As you may know there is problem with packed loss during transmission, which make it nearly impossible to further debug other parts. I have soldered ISP header on the gateway and used is as SPI to attach W5500 PCB. This works just great! I'm back to 100MHz full duplex Ethernet business. With improvements to Webduino library and some other tweaks, it have gained on speed towards web clients, as well as more time to process things internally in RTOS.

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