Pacino flat

pacino_flat

The board for the slim build whose cell sits in a well in the case floor, entirely under the board -- the plate is flat. Cell: 303040 (3 x 30 x 40, ~320 mAh). Case half: variants/5col_extra2_bat303040_pcb_flat.

The two slim builds are two boards, not one board with an option: moving the cell moves the bay, two of the mounting holes and the reset/power positions. The matrix, the footprints and the firmware are identical between them.

Generated by tools/pcb_gen.py -- do not hand-edit pacino_flat.kicad_pcb; change the generator (or keyboard.scad, which the outline and every position come from) and re-run it. There is no schematic file: the generator declares every net and every connection, and names the nets the way the ZMK shield names them.

tools/pcb_gen.py                 # both boards, with gerbers and renders
tools/pcb_gen.py --variant=flat  # just this one
tools/pcb_gen.py --no-render     # skip the raytracing while iterating

20 keys, 39 nets, 557 tracks, 21 vias. Two layers, 1.6 mm, 0.3 mm tracks, 0.2 mm clearance, 0.3 mm smallest drill -- inside every fab's cheapest process.

One board, both halves

The board is reversible: build the left half with the parts on the back, flip the board over and build the right half with the parts on the front. The silkscreen on each face says which half it is. Three things make that work.

Switches. Every switch footprint carries both MX pin diagonals -- the normal pair and its 180 degree rotation -- and a hot-swap socket land on each face. On the right half the switches and the sockets go in rotated 180 degrees; MX switches are square and their stems are symmetric, so nothing about the feel, the keycaps or the plate changes. (Mirroring the pin pair instead, which is the obvious way to do it, puts two 3 mm holes 2.84 mm apart -- they would merge into a slot.)

Matrix. The controller sits on the face opposite the sockets and diodes -- on top of the board, component side towards it, flush in the plate's window -- and flipping the board swaps its two pin rows but not the position along a row, so each hole is one pin on the left half and a different one on the right. The ten matrix holes were chosen so that both of their pins are usable GPIOs and neither is one of pro_micro 1/14/15/16 -- the nice!view's CS/MISO/SCK/MOSI stay free on both halves. The two halves therefore need different pin lists in ZMK -- which is why the slim build has its own shield, pacino_pcb, whose two overlays differ from each other (the hand-wired pacino shield is unchanged and unrelated):

Power. RAW and GND have no symmetric partner, so each gets a three-pad solder jumper: bridge the centre pad to the pad marked L or R for the half you are building. The mark is printed on the face the controller sits on (the face opposite the sockets), and that is the pad to bridge. Boards generated before September 2026 have the letters the other way round: on those, still bridge the marked pad on the controller's face, whatever letter it shows. Reset needs no jumper -- the switch sits across the (rowA,3)/(rowB,3) pair, which is GND/RST one way up and RST/GND the other; a 12 mm tactile links its two legs 12.5 mm apart internally, and the footprint puts those on one net (boards from before the same date have it the other way and short RST to GND: fit the switch by two diagonal legs only).

Assembly

1. Pick your half and work on that face only -- the one whose silkscreen names your half.
2. Diodes: cathode (the bar) towards the marked end. The land takes a SOD-123 on either face, or a through-hole 1N4148 bent to 3.3 mm.
3. Hot-swap sockets, one per key, on the same face -- the silkscreen outlines each one, so the socket goes where its outline is. Right half: rotated 180 degrees; the outlines on that face are drawn that way round, so follow them rather than the other side's.
4. Reset and slide switch: through-hole, bodies on the other face -- they poke up through their windows in the plate.
5. Sockets for the controller on the other face -- the plate side, with the reset and slide switch bodies. The nano sits on top of the board, component side down (towards the board: its USB shell lives in the 3.5 mm socket gap), USB towards the notch in the wall, and finishes flush in the plate's window. The nano's own B+ / B- pads stay empty; the battery reaches it through RAW / GND -- after the slide switch, so charge with the switch on: switched off, the charger sees no cell and its blue LED blinks instead of charging.
6. Bridge JP1 and JP2 to the pad marked for your half.
7. Battery leads to BAT + / -; the cell lies in the floor well beneath them.

Bill of materials (per half)

Plus, from the case: 8 x M2x3x3.5 heat-set inserts, 8 x M2x10 screws, 8 x 10 mm bumpons.

Why the mounting holes are notches

Five of the eight are half-circles in the edge rather than holes through the board; the other three (the thumb end, the bay's bottom corner and the one between the columns) are real holes. That follows from the case: five of its screw bosses sit 0.5 mm inside the inner wall line so they merge into the wall, and the board is the cavity less 0.5 mm -- so those screws' centres land exactly on the board's edge. The other three bosses stand 2.5-3 mm clear of the wall, because the wall keeps rising past the bosses in this build and an insert hole at the wall line would be tucked under it; the five that stay on the line get a 4 mm channel up the inside of the wall instead, so their inserts and screws drop in.

Nothing is bolted through the board. It is clamped: the case's 6 mm bosses come up to its underside and the plate's 5 mm spacer bosses come down onto its top, about 8 mm2 of board between them at each point, and the M2 screw passes through the notch on its way from the plate into the boss. The notches also locate the board -- each one hugs a screw shank, so the board cannot shift in the 0.5 mm of slack around it. Fit the board with the screws out, then drop them through.

Ordering

Two-layer, 1.6 mm, any finish, no controlled impedance. pacino_flat_gerbers.zip is ready to upload. Order it twice over (or ten boards, which is the usual minimum) -- the same board is both halves.