Ethernet PHY Accessory board
With great help from the community I make some good progess with the low-level Ethernet driver. So I think it's time to think about an accessory board with RMII interface. I'm starting a new thread about the hardware, here, so it doesn't get lost in the long discussion about software, timings etc.
The part count is so low that I think it doesn't make sense to make an adaptor board for the Waveshare eval board, instead. Maybe, Parallax is interested in producing and selling the board. If not I'll put it in the public domain or create a sharable project at some board house such as OSHPark.
I've attached my first draft for the schematic. The differences to my current prototyping setup with the Waveshare board are:
- low cost 25MHz crystal instead of 50MHz oscillator
- REF_CLK output mode (better margins for setup/hold times)
- correct polarity of the LEDs
- TXD0 and MDIO share the same pin so everything fits on a single 12-pin header
- RXER is not used