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Bridge keyboards and mice with classic hardware!

The Wombat is a bidirectional ADB-to-USB and USB-to-ADB converter for keyboards and mice.

  • Connect modern USB keyboards and mice to a classic ADB-based Macintosh, Apple IIgs, or NeXT
  • Connect legacy ADB input hardware to a USB-based computer running Windows, OSX, or Linux

No special software or drivers are needed – just plug it in and go.


Now you can finally use a modern optical mouse with your vintage Macintosh, or amuse your coworkers with a retro ADB keyboard on your work machine. ADB-USB Wombat is an indispensable tool for Apple collectors and enthusiasts.


ADB-USB Wombat comes fully assembled and tested.

ADB-USB Wombat  ADB-USB Wombat Input Converter, $49
A bidirectional USB-to-ADB and ADB-to-USB converter. This is the Wombat main board. Optional ADB and USB cables may be purchased separately.
  More Info  

Optional accessories for your Wombat:

ADB-USB Wombat black acrylic case  Black Acrylic Case for ADB-USB Wombat, $9
A glossy acrylic cover to protect and showcase your Wombat board. This is a plate style case with open sides and a logo-etched top. Requires assembly.
  More Info  

ADB Cable, 3 ft  ADB cable 3 ft, $5
For connecting the Wombat to an ADB-based Macintosh, Apple IIgs, or NeXT computer. Standard male-to-male S-video cables from eBay work too.
  More Info  

  Find more items in the BMOW store

ADB-USB Wombat is great for breathing new life into your vintage Apple hardware collection. If you love old Macs, you know ADB keyboards are expensive and hard to find, and ADB mice are sticky and trouble-prone. With the Wombat, you can substitute modern USB input peripherals instead. Or if you swear by your old Apple Extended Keyboard, you can use it with your modern computer. Visitors are sure to smile when they see you running 1980s Apple input peripherals on your 2017 machine.

  • No external power source needed
  • On-board power key for remote turn-on
  • Upgradable firmware
  • Works with your favorite mice and keyboards

The Wombat was developed by Steve Chamberlin, here at Big Mess o’ Wires. See the blog archive for technical details on its software and hardware.


The Wombat hardware is compatible with all Apple computers, keyboards, and mice using a mini DIN 4-pin ADB connector, including most early Macintosh computers, the Apple IIgs, and some NeXT computer models. It is also compatible with standard USB keyboards and mice with a USB-A connector. When in ADB-to-USB conversion mode, it works under Windows, OSX, Linux, or any other operating system that supports USB HID input peripherals.


Connect USB keyboards and mice to a classic ADB-based Macintosh, Apple IIgs, or NeXT computer. Set the Wombat board’s jumpers to USB input mode, as shown on the diagram. Power will be supplied from the computer. Use an ADB cable to connect the board’s ADB port to the computer’s ADB port.

A single USB peripheral can be connected directly to the Wombat board’s USB-A port at CON1, or a standard USB hub can be used to connect multiple peripherals at once. When in this mode, the Wombat supports one USB keyboard and one USB mouse, as well as any number of ADB keyboards and mice, all used simultaneously.

Standard bus-powered USB hubs are recommended. Some externally powered USB hubs (with their own independent power supply) can backfeed power into the Wombat even when it’s off, causing problems.

Most ADB mice had only one button, so the USB mouse’s right button is handled one of two ways. Macintosh mode sends a control + click event to the host, which opens context menus in Mac OS 8 and later. NeXT mode sends a true right click event to the host. Toggle between the modes by clicking the USB mouse wheel button (button 3).

ADB Power Key

Power Key – Original ADB keyboards had a power key – a square or rectangular key with a triangle logo that could be used to turn on some later models of Macintosh computers. There’s an equivalent button on the Wombat board that will function as a substitute power key, even when the computer is off.

Connections for Standby Power

Standby Power – When the Wombat is powered from an auxiliary source, it can continue working even when the computer is off. In this case, the PRINT SCREEN key or F13 key on a USB keyboard will also function as the power key to turn on the computer. To provide standby power, set the board’s jumpers to USB+PWR mode, as shown on the diagram (board version 1.1 or later only). Connect a standard USB charger to the board’s USB-B port at CON2.


Connect ADB keyboards and mice to a modern USB-based computer. Set the Wombat board’s jumpers to ADB input mode, as shown on the diagram. Power will be supplied from the computer. Use a USB-A to USB-Mini-B cable to connect the board’s USB-B port at CON2 to the computer’s USB port. This is the same cable commonly used to connect mobile phones and other devices to a computer. In this mode, nothing should be connected to the Wombat board’s USB-A port at CON1.

A single ADB peripheral can be connected directly to the Wombat board’s ADB port, or multiple peripherals can be daisy-chained, using the ADB pass-through connector found on all Apple ADB keyboards. When in this mode, the Wombat supports one ADB keyboard and one ADB mouse, as well as any number of USB keyboards and mice, all used simultaneously.

The ADB peripherals will appear as standard HID input devices to modern Windows, OSX, and Linux computers. No special drivers or other software are needed.

Firmware Updates

The Wombat firmware can be updated to fix bugs and add new features. Disconnect all power from the board, and set the board’s jumpers to select USB-to-ADB mode. Download the firmware.hex file from the ADB-USB Wombat web page, and copy the file to a USB flash drive. Plug the flash drive directly into the board’s USB-A port – do not use a hub. Hold the board’s power key button while you connect the power and turn on the board. Continue to hold the button for a few seconds, until the A and B status LEDs begin blinking rapidly. The update process takes about 10 seconds. When finished, the LEDs will blink slowly together, once per second. You can now press the power button a second time to exit the firmware update and return to normal input conversion mode.


LED Status Codes

The A and B LEDs on the Wombat board display status and error information. (The A LED is labeled RUN on some boards). During normal use, the A LED will turn on when the Wombat has a working data connection (ADB or USB) to the host computer. The B LED will blink whenever there’s keyboard or mouse activity.

During a firmware update, both LEDs are used to indicate update status:

slow alternating blinks of A, then B (1 blink/sec) – bootloader is searching for a firmware file
fast alternating blinks of A, then B (8 blinks/sec) – bootloader is updating the firmware
slow synchronized blinks of A and B together (1 blink/sec) – bootloader finished successfully

If B blinks several times while A remains off, it indicates a bootloader error:

2 blinks – no valid firmware exists on chip, can’t start main Wombat program
3 blinks – no firmware files found on USB drive
4 blinks – error in firmware file (checksum mismatch or illegal data)
5 blinks – error while updating firmware in chip memory

Help Commands

You can interact directly with the Wombat by typing help commands on an attached ADB or USB keyboard. Open an empty text document or command prompt on your computer. The Wombat will “type” its responses to your commands, so they appear on the screen.

Control-Shift-Capslock-T – Cycles between key mapping types US-GENERIC (ANSI QWERTY), ISO-GENERIC (UK and other non-US QWERTY), ISO-FR (AZERTY), and ISO-DE (QWERTZ)

Control-Shift-Capslock-G – Shows the currently active key mapping type

Control-Shift-Capslock-V – Displays the firmware version number

Control-Shift-Capslock-I – Displays the USB vendor and product ID or ADB handler ID of the keyboard and mouse

Control-Shift-Capslock-C – Enters keydump mode. While in this mode, the USB key code is displayed for each key that you press, along with the corresponding ADB key code it’s mapped to (or vice-versa). This can be helpful for troubleshooting key mapping problems.

Control-D – Exits keydump mode.

International Keyboards

Non-US international keyboards are supported by the Wombat. These include country-specific keyboard layouts like British, Canadian French, Danish, Greek, AZERTY variants, QWERTZ, and others. You’ll need to select the appropriate keyboard type in your operating system’s keyboard control panel, in order for the key mappings to work correctly.

System 7 Keyboard Control Panel

Two specific keys on ISO keyboards may require extra attention. If the key above TAB incorrectly behaves like the key to the right of LEFT SHIFT, you can switch ISO mode on/off to correct it. See details in the Help Commands section.

ISO Keyboard Key Swap

USB-to-ADB – Best results are obtained with Apple-brand country-specific USB keyboards, or any brand US-layout USB keyboards. In many countries, the country-specific PC-type USB keyboards have a different symbol layout than Apple ADB keyboards. These PC-type USB keyboards may be used, but key mappings for some symbols will be incorrect where differences exist between the Apple and PC-type layouts.

ADB-to-USB with Mac OSX – The first time you connect the Wombat to a modern Mac, a wizard will appear and attempt to detect the keyboard type. For non-US keyboards, you should select an ISO keyboard type from the wizard. If the key above TAB incorrectly behaves like the key to the right of LEFT SHIFT, even when the Wombat is in ISO mode, you may need to delete the OSX keyboard preferences to force the wizard to run again. Set the Wombat to ISO mode, delete the file /Library/Preferences/, restart the computer, and follow the wizard steps when it reappears.

Windows 7 Text Services and Input Languages Control Panel

ADB-to-USB with Microsoft Windows – Under Windows, when using country-specific ADB keyboards, you’ll need to select an Apple keyboard sub-type when choosing the keyboard type in the Windows preferences. The keyboard type is selected in the Text Services and Input Languages control panel. E.g. select a keyboard type of United Kingdom (Apple), French (Apple), or German (Apple) rather than the default United Kingdom, French, or German. If you don’t see the Apple sub-types listed, you’ll need to install the Apple keyboard driver applekeyboardinstaller64.exe.

Custom Key Mappings

With firmware version 0.3.0 or later, you can create your own customized key mapping tables. Change which keys behave as Command and Option, reassign the function keys to new purposes, or design other custom mappings. See the Wombat Keymap Tool for details.

What are ADB and USB?

ADB connector

From 1986 through 1998, ADB (Apple Desktop Bus) was the standard system for connecting peripherals like keyboards and mice to Apple computers. It was used by the Apple IIgs, as well as all early Macintosh models except the Mac Plus, 512K, and 128K. The ADB connector is a round mini DIN 4-pin, and is physically identical to the S-Video connector.

USB-A connector

USB (Universal Serial Bus) is the dominant standard today for connecting keyboards, mice, and other peripherals to a computer. Nearly everyone will recognize the familiar rectangular USB-A connector that’s used to plug a device into a host machine. USB replaced a variety of earlier standards like Firewire, ADB, and PS/2. Every Apple computer since 1998 has used USB for its input peripherals.

Converting between the two systems involves more than just a physical plug adapter. ADB and USB high-level protocols are fundamentally very different, and also have different signal speeds, signal formats, and voltages. ADB and USB input peripherals have different communication behaviors too. ADB keyboards and mice use event-based reporting, and only communicate when something has changed, whereas USB keyboards and mice communicate their full current state whenever asked.



ADB-USB Wombat latest firmware version: adb-usb-wombat-0.3.0

Older firmware versions: (try these if the latest version gives you problems)


Get One Now

Check out ADB-USB Wombat at the BMOW Store.


35 Comments so far

  1. Steve May 23rd, 2017 1:41 pm

    If Retro USB is out of stock, please check back again in a few days. I’m assembling more as needed.

  2. Will May 31st, 2017 1:13 am

    There was a bug with the @ and < keys on an AZERTY keyboard. Have you fixed it?

  3. Will May 31st, 2017 1:31 am

    Do you know if any bluetooth adapter could work so I’d have a adb machine with a Bluetooth keyboard?

  4. Steve May 31st, 2017 6:14 am

    Firmware 0.1.8 adds ISO keyboard support, see I haven’t been able to test it on a real ISO keyboard yet, can you let me know how it works for you? Please read the change notes for instructions for deleting your OSX keyboard preferences file, otherwise it may not work correctly.

    Wireless keyboards/mice from Dell and Logitech have been tested and work with Retro USB. I haven’t tried any bluetooth keyboards, but if you have one please let me know what you find.

  5. Steve May 31st, 2017 1:46 pm

    More Retro USB boards are now available for purchase.

  6. Anonymous June 1st, 2017 12:22 pm

    Bluetooth adapters generally will not work, unless the adapter just uses Bluetooth as the wireless mechanism but still present itself as a USB HID device (I don’t know of any such wireless keyboard or mouse that does that).

    I don’t think the Retro USB is a full USB host that can recognize Bluetooth adapters. Steve?

  7. Steve June 1st, 2017 12:44 pm

    There’s certainly nothing Bluetooth-specific in the Retro USB host code. It knows how to talk to USB HID input devices, and (in the bootloader) mass storage devices.

  8. Will June 1st, 2017 2:14 pm

    Well I’d like to order one then and I’ll do some testing and report back here. Both azerty kb and bt adapters.
    How can I get one? It’s still not available in store.

  9. Ruben June 1st, 2017 3:00 pm

    Would a PS2 over USB adapter work ?

  10. Chris M. June 1st, 2017 3:05 pm

    Some of the WIDComm bluetooth dongles will appear as a generic composite USB HID device on boot to allow use of the last paired keyboard/mouse before the OS boots. After the Bluetooth stack loads, it will send a magic keystroke to the HID device and the dongle will switch to being a complete Bluetooth receiver. Apple’s built in bluetooth interfaces did exactly this in Powerbooks.

  11. Steve June 1st, 2017 3:43 pm

    The store shows the current stock status, so if it’s sold out there, you’ll have to try again later. I don’t have a pre-order system, sorry. Eventually supply will catch up to demand. The hardware is designed for standard USB input devices, like the ubiquitous PC keyboard and mouse. For other devices like Bluetooth or PS2 with adapters, you’re in uncharted territory. If the device hides away those details internally, and presents a standard USB HID device interface to the host, then it might work. Try it and let me know what you find!

  12. Steve June 4th, 2017 5:52 pm

    More Retro USB boards are now available in the store. These are version 1.1: same functionality, but fewer jumpers needed for setting the input mode.

  13. Steve H June 4th, 2017 10:53 pm

    Thanks so much for putting the time and effort into this adapter. Finally got my hands on one. Your work is so unique, and incredibly useful/fun.

  14. Steve June 8th, 2017 1:19 pm

    Another batch of Retro USB boards are now available for purchase. I think I’m almost caught up!

  15. David Ludwig June 23rd, 2017 11:41 am

    Has the existing stock of boards been updated to 1.2? I was hoping to get one, and to hook it up to my Apple A1243 keyboard, if possible.

  16. Steve June 23rd, 2017 11:46 am

    Yes, v1.2 is shipping now for new orders.

  17. Joe Seeley June 26th, 2017 9:03 pm

    Just got my retro USB last week. Real dumb question, but others may ask as well: using this with a IIGS, how to emulate Open Apple-Control-Esc and Open Apple-Control-Reset? Figure I must be missing something obvious.

    Thanks for making awesome products for my beloved Apple IIs!

  18. Steve June 26th, 2017 9:14 pm

    Reset = the power key, with the options described above
    Open Apple = the Command key (or Windows key on Windows-centric keyboards). Older ADB keyboards used to have both the open apple and the command cloverleaf icons on the same key, like this example:

  19. Joe Seeley July 3rd, 2017 2:12 pm

    Thanks for the info! I am using a nice wireless keyboard/mouse combo with the Wombat which are approximately the same dimensions of the IIGS originals:

    They work great, just one more dumb question: 1) Which key is mapped to the Option key?

    Thanks again!

  20. Steve July 3rd, 2017 8:28 pm

    If you have Windows-style keyboard, alt = option and windows key = command. It works the same as when using a Windows-style keyboard on a modern iMac or MacBook.

  21. C.L. July 6th, 2017 6:07 pm


    I’m enjoying my USB Wombat greatly. Thanks for making this available! I’m loving the scroll wheel -> arrow keys mapping on the latest FW.

    First, a note: I’ve had mixed luck with PS2->USB adapters. I have an older PS2 KVM that I’m using along with the USB Wombat. On my 1.1 board (with the added capacitor, although that didn’t make a difference) 2 out of 4 USB->PS2 adapters I found worked, while the other two did not. The nonfunctional ones work fine on a PC, but on the Wombat board the mouse and keyboard receive power (apparently) but nothing comes through.

    I ordered a functioning one from Amazon with the name “SANOXY USB to PS/2 Adapter.” I would list the functioning USB IDs, but another adapter I ordered (quite different looking, I should add) has the same USB ID and strings but does not work.

    Second, a request: would it be possible to alter the mapping between Alt and Windows keys on a PC keyboard so that it feels like a Mac keyboard?


  22. Steve July 6th, 2017 8:14 pm

    Are you going PS2 -> KVM -> PS2 -> Adapter -> USB -> Wombat -> ADB -> Macintosh? Wow!!

    I hope to provide user-defined key remapping in the future, as other people have requested something similar. The current mapping for alt/windows matches Apple’s own USB keyboards, where “alt” and “option” are printed on the same key, and I’m following the standard they set.

  23. C.L. July 7th, 2017 5:28 pm

    Yup, there’s also a USB -> PS2 adapter on the mouse before the KVM, but that’s just a pin adapter as far as I know.

    Thanks for the response and thanks again for the product.

  24. Adam Goode September 10th, 2017 8:07 am

    I am typing this on my Apple Extended Keyboard II, and the wombat works great!

    A few things though:
    1. Can we map the Power key on the ADB keyboard? Now that we have keymappings, it should be possible, but I don’t see it in the keymap generator page.

    2. Is it possible to enable right modifier keys? Is it a hardware limitation or can it be enabled? says you need to set a register to enable this.

    Thanks for this great product!

  25. Steve September 10th, 2017 1:12 pm

    Both are theoretically possible, but not implemented due to technical difficulties.

  26. Brielle Marie Harrison October 11th, 2017 11:25 am

    I have the wombat and it has been a true miracle worker for me. I am ordering one of these to solve the two device issue. If it works, you may wish to consider recommending them. They’re only $10

    Cute USB Mini 2-Port USB 2.0 Hub Splitter (Black)

  27. defor November 21st, 2017 9:31 am

    Do you have plans to support Macintosh JIS emulation?

  28. Steve November 21st, 2017 12:31 pm

    No JIS plans at the moment, sorry. Eventually I’d like to open the firmware, so other people could pursue additions that are a bit too niche for me to justify the time required to do it myself. Specific 3rd-party trackpads, gamepads, JIS devices, maybe NeXT-specific stuff, etc.

  29. Charles S. December 1st, 2017 11:07 pm

    Is it possible for the wombat to mount a usb flash drive using OS 9?

  30. Steve December 2nd, 2017 8:08 am

    The Wombat is for HID input devices like keyboards and mice. Even if it were possible to mount external storage devices, it would be excruciatingly slow over ADB – like 1 KB per second. 🙂

  31. Patrik from Germany December 27th, 2017 4:40 am

    Hello Steve! I want to give a huge “thank you!” for this magnificent piece of Hard-/Software! Finally a dream has come true: I can utilize optical mouses on my old Macs. I’m starting to put some money aside so I can get more of these for any Mac I own. 🙂 Again, thanks! Really!

  32. derek January 12th, 2018 10:25 pm

    Thanks so much for creating this little device it is amazing!

  33. Charles H February 2nd, 2018 9:02 pm

    Steve, I have an old Summagraphic’s Bit Pad Plus digitizing pad that was originally used with my Mac Plus – way back when. Would there be any problem using the Wombat to connect that pad to a Mac Pro running OS X? (Fully understanding that the driver is going to be a whole ‘nother can of worms.)

  34. Steve February 2nd, 2018 10:21 pm

    A digitizing pad probably won’t work, sorry. The Wombat can translate standard mouse and keyboard events from ADB to USB, but doesn’t know about other devices like tablets, joysticks, dongles, etc.

  35. Charles H February 3rd, 2018 12:39 pm

    Drats! Well another piece of ancient technology that’ll gather even more dust. But many thanks for your rapid and honest reply.

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