Helpers for creating USB HID keyboards

[amclain]

Creating a USB gadget device that exposes a HID keyboard can involve some cryptic settings, especially for developers who just want to send keyboard events without diving into the USB spec. An example of this configuration can be found in Xebow's hid_gadget.ex file:

# 6-key-rollover descriptor:
# 05 01 09 06 A1 01 05 07 19 E0 29 E7 15 00 25 01
# 75 01 95 08 81 02 81 01 19 00 29 FF 15 00 25 FF
# 75 08 95 06 81 00 05 08 19 01 29 05 15 00 25 01
# 75 01 95 05 91 02 95 03 91 01 C0

# n-key-rollover descriptor:
# 05 01 09 06 A1 01 75 01 95 08 15 00 25 01 05 07
# 19 E0 29 E7 81 02 75 01 95 05 05 08 19 01 29 05
# 91 02 75 03 95 01 91 03 75 01 95 F8 15 00 25 01
# 05 07 19 00 29 F7 81 02 C0

hid_settings = %{
  "protocol" => "1",
  "report_length" => "8",
  "subclass" => "1",
  "report_desc" =>
    <<0x05, 0x01, 0x09, 0x06, 0xA1, 0x01, 0x05, 0x07, 0x19, 0xE0, 0x29, 0xE7, 0x15, 0x00,
      0x25, 0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x81, 0x01, 0x19, 0x00, 0x29, 0xFF,
      0x15, 0x00, 0x25, 0xFF, 0x75, 0x08, 0x95, 0x06, 0x81, 0x00, 0x05, 0x08, 0x19, 0x01,
      0x29, 0x05, 0x15, 0x00, 0x25, 0x01, 0x75, 0x01, 0x95, 0x05, 0x91, 0x02, 0x95, 0x03,
      0x91, 0x01, 0xC0>>
}

AFK could encapsulate USB configuration into one or more helpers, like:

hid_settings = AFK.USB.create_hid_settings(rollover_type: :six_key)

[amclain]

This may be helpful:
https://github.com/ConnorRigby/elixir-libusb

[doughsay]

This may be helpful:
https://github.com/ConnorRigby/elixir-libusb

Correct me if I'm wrong but that library looks like it's meant to interact with USB devices from a host?

[amclain]

Sorry, I didn't mean to imply we should use the library as a dependency. I saw it spits out USB configuration and device data, so thought I'd reference it here in case it can help with figuring out things like n-key rollover.