PC-98 To USB Converter

This converter allows PC-98 keyboards to be connected to modern computers via an Arduino

How to use

1. Connect your keyboard to your Arduino according to the chart below, you can move the pins if you also change them in the Arduino code.

Connection Chart

2. Upload pc98_usb.ino to your Arduino
3. Enable DFU Programmer mode then flash Arduino-keyboard-0.3.hex to your Arduino using dfu-programmer or Flip
   3.2 sudo dfu-programmer atmega16u2 erase
   3.3 sudo dfu-programmer atmega16u2 flash Arduino-keyboard-0.3.hex (Flash Arduino-usbserial-uno.hex to return to arduino mode)
4. Your Arduino/PC-98 Keyboard should act like a USB keyboard.

Layout

Commands

Even though this adapter currently doesn't support sending commands here is a list of the commands the keyboard will accept.

READ

• 0xFA Acknowledged
• 0xFB Not Ready?
• 0xFC Not Acknowledged

WRITE

• 0x95 Enables/Disables the Gui & Menu keys for the keyboards that have them
  0x95 0x00 Disable Gui & Menu keys
  0x95 0x03 Enable Gui & Menu keys

• 0x96 Get current JIS conversion mode
  Returns 0xA0 0x86 = Automatic conversion mode
  Returns 0xA0 0x85 = Normal mode

• 0x99 Unknown, returns 0xFB

• 0x9C Keyboard repeat speed
  Format: 0x9C 01111111
  Bit 7 - Unused
  Bit 6-5 - Delay before repeat (11 = 1000ms, 10 = 500ms, 01 = 500ms, 00 = 250ms)
  Bit 4-0 - Repeat speed (11111 = Slowest, 00001 = Fastest (default))

• 0x9D Keyboard LED Settings
  0x9D 0x60 Returns the LED state in this format: 0000KC0N, K = Kana, C = Caps, N = Num
  0x9D 0111KC0N Sets the LED state, K = Kana, C = Caps, N = Num

• 0x9F Returns the keyboard type Returns 0xA0 0x80 on new keyboards

Key repeating

Repeating scancodes are sent internally from the PC-98 Keyboard, some newer models have a command to stop key repeating but this adapter handles it completely in software so it works on all models.
As a result there is a ~20ms delay (can be changed) when typing but its barely noticeable and no keys are dropped/missed (see typing demo below)

Typing demo

Img.0006.1-1.mp4

Notes

I have only been able to test this with a PC-9801R Keyboard but most other models should work.
The PC-9801V might not work due to it requiring any command to init.
The PTOS Keyboard may or may not work since it uses quite a different layout.

If you have any PC-98 Keyboard please let me know if it works or not.

Resources

TMK PC-9801 Wiki
Hardware Manual - Keyboard Protocol
Hardware Manual - Keyboard Interface
Keyboard Interface & Commands
Different Keyboard Models
Keycodes & Miscellaneous