pikvm/pages/arduino_hid.md

Hardware Arduino HID instead of the OTG

Using Arduino HID on non-v0 platforms is useful if you need a simple and primitive keyboard emulation device. For example, when used with a hardware KVM switch. You can use the firmware to emulate a USB keyboard and mouse, or for the PS/2 keyboard only.

USB keyboard & mouse

• Build and connect HID according to the diagram (the bottom part with transistor, level-shifter and Arduino).
• Switch to RW-mode using command rw.
• Add these lines to /etc/kvmd/override.yaml (remove {} in the file before):

  kvmd:
      hid:
          type: serial
          reset_pin: 4
          device: /dev/kvmd-hid
  

• Create file /etc/udev/rules.d/99-kvmd-extra.rules:

  KERNEL=="ttyAMA0", SYMLINK+="kvmd-hid"
  

• Run systemctl disable getty@ttyAMA0.service.
• Remove console=ttyAMA0,115200 and kgdboc=ttyAMA0,115200 from /boot/cmdline.txt.
• Flash the Arduino HID.
• Run reboot.

PS/2 keyboard

Using the PS/2 firmware currently has the following limitations:

• The possibility of using USB HID is excluded.
• Mouse is not supported due to features of the PS / 2 Protocol.

Both of these problems will be solved one way or another in the future and the two different firmware versions will be combined into one universal one.

To select the PS/2 firmware, you need to follow the instructions for USB, but with one exception. At the device firmware stage instead of commands:

# make
# make install

Use commands:

# make ps2
# make install

Next, you need to connect the Arduino pins to the female PS/2 port of your motherboard. Choose the purple port. If your motherboard only have one port, it's probably universal and can be used either for the keyboard or for the mouse. Most likely, it is painted in two colors: green and purple. You can use it either.

Follow this diagram:

Female PS/2 port (front view)	Pinout
	Arduino pin 3 <-> PS/2 CLOCK Arduino pin 2 <-> PS/2 DATA Arduino GND pin <-> PS/2 GND