Add Cynthion Gateware Tutorials

[antoinevg]

This PR adds three two five Gateware tutorials of increasing complexity to the documentation:

1. Gateware Blinky - Ye olde blinky. Includes instructions for installing the FPGA toolchain and uploading bitstreams.
2. USB Gateware: Part 1 - Enumeration
3. USB Gateware: Part 2 - WCID Descriptors
4. USB Gateware: Part 3 - Control Transfers
5. USB Gateware: Part 4 - Bulk Transfers

NOTE: In the interests of releasing some tutorials sooner rather than later I'll be adding the USB Audio Class Device tutorial in a separate PR.

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Rendered: https://cynthion--197.org.readthedocs.build/en/197/

Depends on:

• Add support for using yowasp when yosys is not available. luna#283
• Add support for using yowasp when yosys is not available. luna-soc#36

[mndza]

That's not really the reason. The avoid_blockram option is enabled because the blockram handler does not support non-contiguous indices for string descriptors, and the Microsoft one needs to be at 0xee. We considered implementing an internal mapping to handle these cases.

[mndza]

I suggest a simpler example here with a SyncFIFO. Note it also blocks the stream when the FIFO is full:

m.submodules.mem = mem = DomainRenamer("usb")(fifo.SyncFIFO(width=8, depth=MAX_PACKET_SIZE))

...

m.d.comb += mem.w_data.eq(stream_out.payload)
m.d.comb += mem.w_en.eq(stream_out.valid)
m.d.comb += stream_out.ready.eq(mem.w_rdy)

m.d.comb += stream_in.payload.eq(mem.r_data)
m.d.comb += stream_in.valid.eq(mem.r_rdy)
m.d.comb += mem.r_en.eq(stream_in.ready)

Since Amaranth HDL v0.5.0, you can do this instead:

wiring.connect(m, stream_out, mem.w_stream)
wiring.connect(m, mem.r_stream, stream_in)

[mndza]

I think the correct thing would be to check for timer == half_freq - 1. This is adding an extra cycle so the blinking period is not 500 ms (but really close!). For that reason, timer could just be Signal(range(half_freq)).

[mndza]

which conform to the Amaranth Data streams <https://amaranth-lang.org/docs/amaranth/latest/stdlib/stream.html>__ interface

This is still not true, right?

[mndza]

This is great! 😃 Added some comments/suggestions.