Simple board consisting of an Atmel ATSAMD21 chip, a USB-A socket (for USB host operation), a micro USB socket (for USB device operation), a voltage regulator, and an SWD header.
The ATSAMD21 is a cheap ($1-2) microcontroller that can act as a USB host, which I plan to use to connect USB keyboards to my currently-keyboardless Master 128 and Beeb motherboards.
This works nicely with Atmel START, but that generates a ton of boilerplate code, so I'm looking to see if I can use anything simpler, and hopefully compatible with the code I'm writing for the Pro Micro.
I've successfully gotten it running using MattairTech's SAMD21 Arduino port.
I can't use the bootloader for my project, because I want to have the USB port in host mode. Luckily Arduino has arduino-builder, which makes it easy to make a Makefile. This generates a .bin file, which I can write into the chip using a J-Link script.
For a working example, see third_party/usb_keyboard_forwarder.
r1: Sent to oshpark.com for fabrication 2017-11-06. Assembled and tested; appears to work. Functions fine as a USB CDC device, and as a host for a mouse using code generated by Atmel START.
