Fujitsu 3rd Gen Leafspring Teensy Wired

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30 Jul 2017, 00:41

I picked up a Fujitsu N860-2500-T111 board with 3rd gen leaf spring switches. I couldn't find out much about the protcol used (which seems to be common with a number of older terminal boards) and wanted to get the board usable so I traced out the matrix with a multimeter and soldered wires to the IC pads and connected the Teensy. I was concerned there might be problems with cross currents but it's working. Hasn't caught on fire yet either.

c_wired.jpg (195.78 KiB) Viewed 1950 times
b_wired.jpg (134 KiB) Viewed 1950 times
switches1.jpg (298.07 KiB) Viewed 1950 times
switches2.jpg (289.05 KiB) Viewed 1950 times
d_board.jpg (191.38 KiB) Viewed 1950 times

The switches are clicky linear and have a nice feel. I'm curious how people feel the 3 generations of leaf springs compare. I've never tried a 1st or 2nd generation board. This wiring job worked but is anyone aware of any protocol converters out there for the older Fujitsu boards?

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chip chop

06 Aug 2017, 18:26

Nice project, I imagine the switches are nice and smooth with that switch design, with the plunger directly pressing the contact instead of dragging past it. Think the earlier gen switches are found on more exotic boards, Sanyo MBC-2000 etc.

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Offtopicthority Instigator

06 Aug 2017, 18:34

Ohh how did I miss this ?!? :o :shock: Great job OldIsNew ! It happens I own almost exactly the same keyboard!

keyboards-f2/fujitsu-limited-n860-2505- ... %20T00201A

No, I am not aware of any protocol converters out there for the older Fujitsu boards. So how do you like those Fujitsu 3rd Gen Leafsprings?
chip chop wrote: Nice project, I imagine the switches are nice and smooth with that switch design, with the plunger directly pressing the contact instead of dragging past it.
That's the brilliance of this switch design, no friction!

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[ XMIT ]

07 Aug 2017, 03:46

I have one of these boards too! Awesome to know that the mod is so easy.

Oh weird, you have the same inverted-Q looking 'O' key! I thought that was just mine. What's the deal with that?!

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08 Aug 2017, 07:49

An update and some more info. While the board seemed to work fine at first with just soldering directly to the intact IC pads, as I used it more I started to notice extraneous keys registering with key presses from time to time. This seemed somewhat random and I began to suspect that there were issues with stray current - I guess not too surprising considering the direct wire job (I thought I had gotten away with it). Hoping this was it, I went ahead and desoldered the ICs I had soldered to, and the main one while I was at it, and resoldered directly to the pads. This appears to have solved the problem and I'm not getting any more extra key presses.
Desoldered1.jpg (557.5 KiB) Viewed 1787 times
Desoldered2.jpg (352.08 KiB) Viewed 1787 times
I'm posting the keyboard matrix I came up with using the multimeter. The matrix is correct for my board so I would think it should be usable if you have the same board. The matrix also includes the Teensy++2.0 pins and the wire assignments used in firmware (so obviously only relevant to the software I'm using). For firmware I'm using Arduino C code that works but is far from elegant (e.g. lines of code for each key rather than using arrays). I just haven't gotten around to rewriting it and cleaning it up. If anyone wants a copy I'm happy to send it - just don't ridicule it too much! The coding was just part of the hobby for me - I would think TMK could be used as per matt3o's tutorial: workshop-f7/how-to-build-your-very-own- ... t7177.html for some professional style firmware.

Below are the key matrix and a pic with labels of the pins I used on the PCB:
jujitsu_matrixB.jpg (283.6 KiB) Viewed 1787 times
Fujits_PCB_pinout.jpg (701.52 KiB) Viewed 1787 times

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Offtopicthority Instigator

08 Aug 2017, 11:03

Thanks for sharing your details for the pins, great job with that picture for the Teensy++2.0.

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10 Aug 2017, 07:09

Finished with the wiring. The Teensy++ fit nicely where the main IC was. Typing on the board now.
wired.jpg (266.73 KiB) Viewed 1721 times
case.jpg (204.17 KiB) Viewed 1721 times

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Offtopicthority Instigator

10 Aug 2017, 07:25

Nice work and check out what a pretty version of this Halvar got:
Fujitsu (Medium).jpg
Fujitsu (Medium).jpg (232.54 KiB) Viewed 1713 times

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10 Aug 2017, 08:28

Great project OldIsNew, and thanks for documenting it so thorougly! I'm really inclined to get my soldering iron out on the weekend.

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23 Sep 2020, 09:10

Thanks, OldIsNew! I've used your matrix pinout info to run QMK on this beautiful keyboard.
QMK link

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