PolyKybd Split72

Official hardware repository of the PolyKybd Split72 keyboard. If you are looking for the kit, jump immediately to https://www.crowdsupply.com/polykybd/polykybd for registration.

The instructions here are still in a very early stage. There is also a build video available: https://www.youtube.com/watch?v=K5RpbYzx7gw

You can find the matching QMK firmware here: https://github.com/thpoll83/qmk_firmware/tree/PolyKeyboard

The KiCad7 projects for the PCB are the following:

poly_kybd/poly_kb_wave_right2.kicad_pro poly_kybd/poly_kb_wave_left2.kicad_pro

(wave was the the prototype name, please just ignore the other projects)

The keyboard plates are also KiCad7 projects (I used 1.2mm aluminum PCBs):

poly_kybd/poly_kb_wave_right2_plate.kicad_pro poly_kybd/poly_kb_wave_left2_plate.kicad_pro

How to Build

I recommend waiting for the kit that contains all parts and the assembled PCBs. Here a little preview, how that looks like: The kits are not yet ready, but you can sign up here and get notified as soon as these are available: https://www.crowdsupply.com/polykybd/polykybd

At the moment, please consider these instructions as experimental. If you want to go ahead with the full experience and build everything from scratch right now: Give it a try and let me know how it worked out!

Independent of your choice, here are the parts you need before putting everything together:

Prepare Required Parts

• Case (left/right) - You can either 3D print or get them CNCed (but then you should add some threads to the screw holes): case/case_polysplit72_left2_r4.stl case/case_polysplit72_right2_r4.stl In case the resin print has some deformations, it is best to use the a hairdryer to slightly heat the case up and then put something heavy on the bottom to make it flat - it really works.

• Spacer to keep the right distance between plate and PCB (again, can be 3D printed): case/spacer.stl

• Assembled 4 layers PCB 1.6mm (left/right) The latest gerber files with BOM and pick/place file can be found in poly_kybd/Gerber I made some final adjusts on the latest version, which I did not yet order (I will let you know as soon as I did). poly_kybd/Gerber/PCB/left-side-v3.1/gerber-left-side-v3.1-08.01.2024.zip poly_kybd/Gerber/PCB/right-side-v3.1/gerber-right-side-v3.1-08.01.2024.zip

  

  My recommendation is to let assemble the PCBs as there are a lot of parts with tiny footprints like the RP2040, the 72 FPC sockets and some more... If your PCB fab has an option to verify the parts orientation, please make use of it. I did that as well and never bothered correcting them (since the 'upright' orientation of the part from KiCad and your PCB fab might differ).

  Note:

  In case you make modifications to the PCB in KiCad and export everything you might need to change the hot swap sockets side to the back. The hot swap socket in KiCad is part of the key switch and for some reason I couldn't yet convince KiCad that the manufacturing side is the back...

• Aluminum plates (left/right =) - Can be ordered from PCB manufactures as a 1.2mm aluminum PCB poly_kybd/Gerber/Plate/gerber-left-side-v3-17.11.2023.zip poly_kybd/Gerber/Plate/gerber-right-side-v3-17.11.2023.zip

• Displays

  • 72 pieces 0.42 inch displays

    • Either you take the 0.42 inch displays from the kit which has the matching length and pin number (maybe I can make them available as single parts as well - see picture above, on the left).
    • Or you extend *FPT042W000Z01 or *P34107 with a 30mm FPC cable ( * I got contacted that these Alibaba links are stale and it turned out, that the moment, these do not work as the displays got removed. Let me keep them in case they come back online. Maybe you can use these as alternative, the pins are compatible: ZJY042-7240TSWPG10 The flex cable is about 1cm shorter, so your extension needs to be 40mm instead of 30mm. I have not tried these, so you might wanna do a test first!). The FPC extension should be 14 or 16 pins - blank contacts on the same side, like the two right side displays on the picture above. Only 14 pins are needed, however, you might want to get a 16 pin FPC and cut away 2 pins to fit the FPC into the 14 pin socket. It is easier to solder 16 pins of the display together with the 16 pins of the FPC (so the cable aligns), see here: To achieve this, I applied low temperature solder (138 degree C) on both, the display FPC pins and the extension FPC pins with the solder iron: Then applied some flux on just one side and orientated them straight - don't overlap the pins 100%, leave some space at the end so that excess solder can have some space to escape: Next, I used the heat gun with maybe 160 C and heated both sides for a few seconds (you can see the solder becoming liquid again): Finally use some tweezers to push the pins together. You will see some solder coming out at the non-overlapping part of the pins I mentioned to leave out. This is also a good way to see that all pins have sufficient solder and will connect properly: Not every display survived this surgery, so better get more from the beginning.

  • (Optional) 2 pieces 0.96 inch status displays (FPW096W001Z0) or pin compatible (see below), the flex cable length should be about 40mm or you extend it on your own. You can contact this supplier: FET, they have these displays even they are not listed in their online catalogue.

    | PIN | SIGNAL | PIN | SIGNAL | | ----- | --------- | ----- | ------ | | 1,30 | N/C (GND) | 14 | RES# | | 2,3 | C2P,C2N | 15 | D/C# | | 4,5 | C1P,C1N | 16 | R/W# | | 6 | VDDB/VBAT | 17 | E/RD# | | 7 | N/C | 18~25 | D0~D7 | | 8 | VSS | 26 | IREF | | 9 | VDD | 27 | VCOMH | | 10~12 | BS0~BS2 | 28 | VCC | | 13 | CS# | 29 | VLSS |

    If you don't need the status displays, you can close the display cut-out with the dummy holder: Dummy Display Holder

• MX Compatible key switches (3 or 5 pins) - 72 pieces. From my blog post ( https://ko-fi.com/post/More-Key-Switch-Testing-While-Waiting-For-The-Asse-B0B8HX1HW ), you can find out, that there are 2 categories of compatible key switches. The ones that work out of the box and the ones that need a little modification. Basically all switches that have an LED slit that is at least 7.5mm wide work. I tested quite some switches and here is the list of tested switches that will work for sure without modification:

  | SWITCH | TYPE | MISC | | --------------------------------- | --------------- | ----- | | Aflion Tropical Waters | Linear | 68g | | Ashkeebs Alexandrite | Linear | 58g | | Blue Dusk Panda | Linear | 62g | | CK x Haimu Pastel Lemon | Linear | 63.5g | | Ck x Haimu Pastel Thistle | Tactile | 63.5g | | Gateron KS-9 (Pro) Blue | Clicky | 60g | | Gateron KS-9 (Pro) Brown | Tactile | 55g | | Gateron KS-9 (Pro) Green | Clicky | 80g | | Gateron KS-9 (Pro) Red | Linear | 45g | | Gateron KS-9 (Pro) Yellow | Linear | 50g | | Geon Black | Tactile | 60g | | Geon Clear | Linear | 60g | | Geon Yellow | Linear | 63.5g | | Glorious Panda | Tactile | 67g | | GOJU Works x Tecsee Safety Switch | Linear | 65g | | Kailh Novel Keys Cream Switch | Linear | 55g | | Kailh Purple Potato | Tactile | 63.5g | | Kailh x Domikey Knight Saber | Tactile | 42g | | LCET Grace | Linear | 50g | | LCET Joker | Tactile | 58g | | LCET Pink Queen | Tactile | 58g | | LCET Sprout | Linear | 50g | | Outemu (Dustproof) Black | Linear | 65g | | Outemu (