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[TMK] FC660C Alt Controller

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What is this?
This controler replaces original controller of Leopold FC660C and makes the keyboard programmable.
This is supposed to be compatible to all variants of FC660C as of 2019-05-03.

Type-C version is available now. 2023-11-28

This pic shows Type-C version on top and Mini-B on bottom.

Check this thread for technical infos and discussion of the controller:

GB thread of past rounds(for the record):

Post your question or suggestion here.


This controller is still regularly available in stock and can be shipped from Japan in a week. (2023-08-25)

Email me at with subject "FC660C [Mini-B or Type-C]" to place an order. Just let me know  your location(country).  I'll send PayPal invoice to your email address. Do not PM(Private Message) me.

The controllers will be available regularly and can be shipped in a few working days.

Price: 44USD for Mini-B
Price: 46USD for Type-C

Payment: I'll send you PayPal invoice, you can pay  with credit card or balance of PayPal account. Please make sure you supply correct shipping address when making payment.

Shipping: Please check this notes.
Via Registered mail and usually takes two weeks. Trackable in most of countries except for Canada, Australia and China. Shipping cost is same rate for all countries as far as Japan Post can cover. Your item will be shipped within a week.

Type-C controller
Difference is only its USB conector. Other part of controller is identical to Mini-B controller.

You don't have to modify or file its case basically. Type-C receptacle on the controller fits into the existent opening like below.

But space around receptacle is a bit tight for Type-C plug.

Note that all Type-C cables don't fit with FC660C due to the narrolw space(12.15mm). Width of Plastic blob of plug is important here. You can not use cable with wide plug physically.  Pushing a big plug into forcibly can damage the case.

Use Type-C cable with small plug and don't insert by force.

I tried several cables whose plastic blob width are: 12.42mm, 12.21mm, 11.33mm and 10.63mm.
Leftmost one cannot be inserted, second one is tight but can be pushed into somehow, others has no problem.

How to install
You need only screw driver to install this controller. No soldering is required.

And take a look this video. Thank you, stoic-lemon!

Open case
You have to void warranty from manufacturer to do this mod, of course.
MoreStep 1: Void your warranty with getting rid of sticker and unscrew.

Step 2:  Crack it open using tool like phone openner or plastic card with care.

Step3: Done!

Mate/unmate connector
Check image below to know how to mate/unmate connector.
More I recommend you follow method proposed by manufacturer and this works certainly for me.
You don't need any tool to remove/unmate the connector use just your fingers. Plier and screwdriver likely slip off and make scratch and give cables damage.
To remove/unmate hold many cables as possible with thumb and index finger and wiggle the connector laterally each side within 15deg range.
To insert/mate just push both side edge of the connector parallel with fingers or nails.

Install controller board
Just screw down controller PCB on case.

How to remap
Keymap Editor
You can use online keymap editor to get prebuilt firmware with your own keymap.

MoreThere are two kind of prebuilt firmware. Plain one has very simple keymap and  would be useful as start point if you want to define you own keymap from scratch. Emu one emulates FC660C stock behaviour, it would be nice if you like the stock keymap basically and need only small change.

- Plain:
- Emu:

LED control
CapsLock LED indicates CapsLock state naturally in both Plain and Emu firmware.
Insert LED never light up with Plain firmware, which suits for people who have no plan on the LED or regard it distractive. Emu firmware turns Insert LED on when Layer 1 is activated, you can you can place your keymap there and make it indicator for your keymap state.
Not a fan of these behaviour? You can do anything with the LEDs if you willing to write small code, of course.

Keymap Examples:
- hasu's: spacefn and mousekey(Emu)
Share your keymap! Use 'URL shortener' button on keymap editor to get URL of your keymap and post it here.

You can grasp how this works by watching stoic-lemon's video.

How to flash
TMK FC660C Alt Controller has ATMega32U4 as a microcontroller. To boot the microcontroller into programming mode push button on bottom of keyboard.

See wiki page on github for detail of flashing tool.

Build from source codes
You can also tweak sources if keymap editor is not enough.

See this for detail.

- No plan for USB-C C is a bit too large to plug in USB-mini hole. More
- No Bluetooth  This controller doesn't support Bluetooth, USB only.  And check my thought as of July 2019.
- Not for FC980C This is not. See FC980C Alt Controller thread.
- Not for FC660M, FC750R and others... It is not possible to replace its controller on the keyboards. This controller is only for FC660C definitely.
- Actuation point adjustment Not officially supported. See this post.

- For new 'Made in Japan' models The controller works fine with the new 'Made in Japan' model also. see this post.

Check FAQ on wiki first.

- Doesn't work with BIOS/UEFI
- Switching NKRO/6KRO

2017/04/06 GB OPEN:
2017/05/01 GB CLOSE
2017/05/19 GB SHIPPED
2017/06/29 Open thread inTMK Keyboard Service subforum
2018/05/21 Add Note for "Made in Japan" models and  update stock
2018/09/15 Update error of pin configuration in documentation(PB7-> PB6).
2021/03/29 Revised shipping rate
2023-11-28 Type-C version is available now.

Restocked eight controllers now.

This is in production regularly and available in stock.

Just confirmed now that this controller works fine with new 'Made in Japan' model also.

Have got similar question from potential buyers sporadically, it is worth to answer it here.

--- Quote ---do you currently offer the Alt controller for the Leopold FC660C with Bluetooth support?
If you don't currently have the controller with Bluetooth supoort, would too be releasing one with this supoort any time soon?

--- End quote ---

No, Bluetooth support is not available for FC660C from me and no plan at this time.

Here in Japan FC660C is compeltely out of stock and the product seems to be end of life in this country at least unfortunately. I'll have to check future supply of the product first before makng a plan for new controller.

But I'm still interested in designing Bluetooth controller/keyboard for myself, and will keep watching and researching related technologies and develpments in keyboard community.


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