USB2Sun

While I've found many projects for connecting the Sun serial based keyboards to a modern machine via USB, I've never found anything to connect a USB keyboard onto a classical Sun workstation.

This project allows you to connect a USB keyboard and mouse to a Sun workstation, using a Raspberry Pico as a bridge.

I've used two SN74LVC244AN as level shifters, one for 3.3V to 5V (from Pico to Sun), and one for 5V to 3.3V (from Sun to Pico). There are probably smaller shifters than the octal shifter I found, but I couldn't find any.

The Pico board is powered by the Sun workstation's 5V supply.

This project is currently targetting Pico SDK 1.5.1, and the corresponding TinyUSB version.

Features

• Emulate the left keyboard function keys by entering LeftShift+LeftControl and the corresponding key

  PC	Function
  F1	Stop
  F2	Again
  1	Props
  2	Undo
  Q	Front
  W	Copy
  A	Open
  S	Paste
  Z	Find
  X	Cut

  Breaking into OpenFirmware would be LeftShift+LeftControl+F1+A

Missing Features

• Keyboard power on. Shorting minidin pin 7 to 5V rail powers on the system, however, the 5V rail is unpowered when the system is off - so the Pico is also unpowered in this state.
• LED indicators (num - caps and scroll lock).
• Switching layouts. PC or Unix layout and international layout (the emulated keyboard responds US for now).

Build

Make sure the Pico SDK has been checked out, as detailed by the Pi foundation.

mkdir build && cd build
PICO_SDK_PATH=../../pico-sdk cmake ..
make

If your flashing with a Raspberry Pi, flash the firmware using

openocd -f interface/raspberrypi-swd.cfg -f target/rp2040.cfg -c "program usb2sun.elf verify reset exit"

Or copy usb2sun.uf2 onto the Pico when it's in flash mode.

Usage

Connect a USB mouse and keyboard using the OTG adapter. Wireless combo sets will work best, as they do not require a hub.

The project can be either plugged directly into the keyboard port on the workstation, or daisy-chained to a Sun keyboard. If daisy-chaining to the keyboard, do not connect the UART1 pins (6 and 7), only connect UART0 TX (1) to the Mouse TX pin on the minidin.

Parts required

• Raspberry Pico
• 8 pin minidin male cable (I used https://no.rs-online.com/web/p/din-cable-assemblies/0463518)
• 2 SN74LVC244AN
• USB OTG adapter

Wiring

Raspberry Pico

 UART0 TX   * Pin  1-----|USB|------Pin 40 *   5V
            * Pin  2     `‾‾‾´      Pin 39 * 
            * Pin  3                Pin 38 *   GND
            * Pin  4                Pin 37 * 
            * Pin  5                Pin 36 *   3V3
 UART1 TX   * Pin  6                Pin 35 * 
 UART1 RX   * Pin  7                Pin 34 * 
            * Pin  8                Pin 33 * 
            * Pin  9   .--------.   Pin 32 * 
            * Pin 10   |        |   Pin 31 * 
            * Pin 11   | RP2040 |   Pin 30 * 
            * Pin 12   `--------´   Pin 29 * 
            * Pin 13                Pin 28 * 
            * Pin 14                Pin 27 * 
            * Pin 15                Pin 26 * 
            * Pin 16                Pin 25 * 
            * Pin 17       π        Pin 24 * 
            * Pin 18                Pin 23 * 
            * Pin 19                Pin 22 * 
            * Pin 20----------------Pin 21 * 

5V to 3V3 level shifter

      GND   * Pin  1----------------Pin 20 *   3V3
   KBD RX   * Pin  2                Pin 19 *
            * Pin  3                Pin 18 *   UART1 RX
            * Pin  4                Pin 17 *
            * Pin  5  SN74LVC244AN  Pin 16 *
            * Pin  6                Pin 15 *
            * Pin  7                Pin 14 *
            * Pin  8                Pin 13 *
            * Pin  9                Pin 12 *
      GND   * Pin 10----------------Pin 11 *

3V3 to 5V level shifter

      GND   * Pin  1----------------Pin 20 *   5V
 UART1 TX   * Pin  2                Pin 19 *
            * Pin  3                Pin 18 *   KBD TX
 UART0 TX   * Pin  4                Pin 17 *
            * Pin  5  SN74LVC244AN  Pin 16 *   MOUSE TX
            * Pin  6                Pin 15 *
            * Pin  7                Pin 14 *
            * Pin  8                Pin 13 *
            * Pin  9                Pin 12 *
      GND   * Pin 10----------------Pin 11 *

MiniDin-8 plug

        , - ~._.~ - ,
    , '               ' ,
  ,     6     7     8     ,
 ,                         ,
,                           ,
,    3    4           5     ,
,                           ,
 ,                          ,
  ,_      1      2       _,
    `-.              .-´
      ' - , _ _ _ , -'

Pin	Function
1	GND
2	GND
3	5V
4	MOUSE TX
5	KBD RX
6	KBD TX
8	5V