Copy+comment atsamd-usbd-uart

Has a little debug code left from
atsamd-rs/atsamd#459

atsamd-usbd-spi/Cargo.toml

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+[package]
+name = "atsamd-usbd-spi"
+version = "0.1.0"
+authors = ["Ian Rees <code@ianrees.nz>"]
+keywords = ["no-std", "arm", "cortex-m", "atsamd", "usb", "embedded-hal"]
+edition = "2018"
+
+[dependencies]
+# Using bbqueue because it gives a low-cost method to attempt a USB write,
+# without removing data from the structure, where heapless::spsc would seem to
+# require an intermediate buffer.
+bbqueue = {version = "0.4.12", features = ["thumbv6"]}
+
+cortex-m = "~0.6"
+
+# TODO Remove defmt before publishing?
+defmt = "0.2.0"
+defmt-rtt = "0.2.0"
+
+usb-device = "0.2.7"
+
+[dependencies.atsamd-hal]
+# TODO stop using this
+path = "/home/irees/Projects/20201112 - atsamd-rs/hal"
+
+# TODO specify as a minimum version of atsamd-hal once the UARTv2 PR is merged
+features = ["usb"]
+
+[features]
+default = [
+    "defmt-default",
+]
+
+defmt-default = []
+defmt-trace = []
+defmt-debug = []
+defmt-info = []
+defmt-warn = []
+defmt-error = []

atsamd-usbd-spi/README.md

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+atsamd-usbd-spi
+===
+
+Work in progress toward a firmware USB Class for ATSAMD parts, which implements a USB-to-SPI-master.
+