Glossary

Every term this book leaned on, in plain language, grouped by first letter so you can skim. Where a chapter teaches the term properly, the entry points there.

A

Anti-ghosting. A keyboard's ability to report every key you actually press, with no phantom extras, even in combinations. On boards like the Lily58 it comes from giving every switch its own diode (see Chapter 1).

ATmega32u4. The small chip at the heart of the classic Pro Micro controller. Reliable and long-serving, but slower and with far less memory than the RP2040, and its flashing procedure is fussier (see Chapter 12).

B

Bootloader. A tiny factory-installed program on the controller whose only job is to receive new firmware. You wake it with a double-tap of the reset button; on RP2040 boards it shows up on your computer as a USB drive named RPI-RP2.

Bridge (solder). A blob of solder accidentally connecting two pads or pins that should stay separate, causing shorts and phantom keys. Fixed with desoldering wick (see Chapter 8).

C

Choc switch. A low-profile switch format made by Kailh, flatter than the standard MX style, with its own incompatible sockets and keycaps. Some Lily58 PCB variants support Choc; this book builds the MX version (see Chapter 2).

Cold joint. A solder joint where the solder never properly bonded to the pad or pin, usually because the parts were not heated enough. It looks dull, grey, or grainy instead of shiny, and it fails electrically now or later (see Chapter 6).

Columnar stagger. Arranging each finger's keys in a straight vertical column, offset up or down to match that finger's length, instead of the diagonal offsets of a normal keyboard. The Lily58's defining shape, and the reason for the two-week adaptation dip (see Chapter 14).

Continuity. An unbroken electrical path between two points. A multimeter's continuity mode beeps when a path exists, which makes it the referee for "is this joint actually connected" (see Chapter 13).

Controller. The small computer board (Pro Micro, Elite-Pi, Frood, nice!nano) that runs the firmware, scans the matrix, and talks USB. Each half of the Lily58 has one, and this book sockets them so they can be swapped (see Chapter 3 and Chapter 10).

D

Debounce. The short wait (a few milliseconds) the firmware imposes after a key event, to filter out the rapid mechanical flutter of metal contacts closing. Too little debounce and keys chatter, registering twice per press (see Chapter 13).

De minimis. The value threshold below which an imported parcel enters Canada without duty. Relevant when ordering kits and parts from US and overseas shops (see Chapter 4).

Desoldering wick. Braided copper ribbon that soaks up molten solder like a sponge when pressed onto a joint with the iron. The tool for removing bridges and emptying joints (see Chapter 8).

Diode. A one-way valve for electric current. One sits behind every key so the controller can tell exactly which keys are pressed in any combination; soldered backwards, it causes phantom letters (see Chapter 1).

E

EEPROM. A scrap of memory on the controller that survives power-off. QMK uses it to remember settings such as which half of the split is the left one (see Chapter 12).

ESD. Electrostatic discharge: the static-shock zap that can silently damage chips. Handled with basic habits, like touching something grounded before handling the controller (see Chapter 9).

F

Fillet (solder). The smooth cone shape of solder rising from pad to pin on a good joint, like a tiny volcano or a Hershey's Kiss. The shape your eye learns to demand from every joint (see Chapter 6).

Firmware. The program stored on the controller that scans the matrix, applies the keymap, and speaks USB HID to the computer. QMK, Vial-flavoured QMK, and ZMK are the firmwares in this book's world (see Chapter 12).

Flux. A chemical that cleans oxide off metal surfaces at soldering temperature so the solder can bond. Some lives inside the solder wire (rosin core); more comes from a flux pen for rework (see Chapter 6).

FR4. The green (or black, or purple) fiberglass-and-resin material that circuit boards are made of. Sturdy, but not something to pry against carelessly.

G

Ghosting. Phantom keypresses: the computer receiving a key you never pressed, classically when three corners of a matrix rectangle are held and the fourth appears on its own. Per-key diodes eliminate it; a backwards diode reintroduces it (see Chapter 13).

H

HID (USB HID). Human Interface Device, the standard USB language for keyboards and mice. Because the firmware speaks HID, your hand-built board needs no drivers on any operating system (see Chapter 12).

Hotswap socket. A small metal-and-plastic clip soldered to the PCB that grips a switch's pins, so switches push in and pull out by hand with no soldering. You soldered 58 of them per this book; the payoff is swapping switches forever after (see Chapter 10).

K

Key matrix. The grid wiring scheme where switches share row wires and column wires, letting a controller with a couple dozen pins read 58 keys. The firmware scans it many times per second (see Chapter 1).

Keycap profile. The family of shapes and heights a keycap set is sculpted in. Cherry and OEM are sculpted (each row a different shape, like most store keyboards); SA is tall and dramatically sculpted; DSA and XDA are uniform (every key the same flat-topped shape), which suits columnar boards because any cap fits any position (see Chapter 4).

L

Layer. One complete keymap in a stack of them; holding a layer key switches which one is live, the way Shift has always switched letters to capitals. Small keyboards replace missing keys with layers (see Chapter 12).

Leaded / lead-free solder. The two families of solder wire. Leaded (typically 60/40 tin-lead) melts lower and flows more forgivingly; lead-free is what industry now uses and needs a slightly hotter iron. Either builds this keyboard fine; wash your hands after leaded (see Chapter 5).

LiPo. Lithium polymer, the small flat rechargeable battery used in wireless keyboard builds. Needs respectful handling: no punctures, no shorting the leads (see Chapter 2).

M

Master / slave. In a split keyboard, the half with the USB cable (master) talks to the computer and polls the other half (slave) over the TRRS cable. Newer documentation often says central / peripheral for the same roles (see Chapter 12).

Mill-Max. A brand of precision socket pins, used to socket a controller so low that low-profile builds still close. The generic word for the cheaper alternative is machine-pin or round-pin sockets (see Chapter 10).

MX stem. The plus-sign-shaped post on top of a standard mechanical switch that keycaps grip. "MX-compatible" on a keycap or switch means this de facto standard, named for the original Cherry MX switch.

N

N-key rollover. The ability to register any number of simultaneous keypresses correctly. A per-key-diode board running QMK has it naturally.

nice!nano. The most popular wireless Pro Micro-compatible controller: same footprint, plus Bluetooth and battery charging. Runs ZMK, not QMK (see Chapter 2).

O

OLED. The small monochrome screen (an SSD1306 module in the Lily58's case) that can show the current layer, a logo, or whatever the firmware draws. Optional, charming, occasionally blank until you check the jumpers (see Chapter 10 and Chapter 13).

Ortholinear. A key grid with straight columns and straight rows, no stagger at all (the Planck is the famous example). The Lily58 is columnar staggered, not ortholinear: its columns are straight but vertically offset per finger.

P

PBT / ABS. The two common keycap plastics. PBT is matte, textured, and resists developing shine; ABS is smoother, cheaper, and polishes shiny under fingers over months. Both type identically (see Chapter 4).

PCB. Printed circuit board: the fiberglass board with copper traces that carries every component and connects them. The Lily58 kit has one per half (see Chapter 3).

Perfboard. A generic practice circuit board covered in a grid of plated holes. What you solder your first hundred joints into before the real kit (see Chapter 7).

Plate. The rigid sheet (usually FR4 or metal) that switches clip into, sitting above the PCB and holding every switch straight and firm. On hotswap boards the plate is structural, not optional (see Chapter 11).

Pro Micro. The small ATmega32u4 controller board whose size and pin layout became the standard footprint for DIY keyboards. "Pro Micro-compatible" describes any controller with the same footprint, including the RP2040 drop-ins this book prefers (see Chapter 2).

Q

QMK. The open-source firmware that powers most wired custom keyboards, the Lily58 included. Configured rather than written: a keymap is a list of key names (see Chapter 12).

R

Reversible PCB. A circuit board designed so the identical board serves as either the left or the right half, depending on which side you solder the components onto. The Lily58 uses one, which is why "solder on the correct side" gets repeated so much (see Chapter 9).

Rosin core. Solder wire with flux built into its center, so every joint gets cleaned automatically as the solder melts. The only kind of solder wire to buy for electronics (see Chapter 5).

RP2040. The chip from the Raspberry Pi organization that powers modern Pro Micro-compatible controllers like the Elite-Pi and Frood. Fast, roomy, cheap, and flashable by drag and drop, which is why this book recommends it (see Chapter 12).

S

SMD / through-hole. The two ways components attach to a PCB. Through-hole parts have wire legs that pass through holes and are soldered on the far side; SMD (surface-mount device) parts sit flat on pads on one side. Hotswap sockets are SMD but with big friendly pads, which is why beginners manage them (see Chapter 6).

Split keyboard. A keyboard in two independent halves, one per hand, connected by a cable, so each half sits where the hand and shoulder want it (see Chapter 1).

Standoff. A small threaded metal or brass pillar that holds the plate at a fixed height above the PCB, screwed from both sides. The skeleton of the case sandwich (see Chapter 11).

Switch (linear / tactile / clicky). The mechanism under each key. Linear switches move smoothly with no feedback; tactile switches have a small bump you feel at the actuation point; clicky switches add an audible click to the bump. Feel is personal; hotswap lets you change your mind (see Chapter 1).

T

Tenting. Tilting each half of a split keyboard so the thumb side rises, rotating your wrists toward a natural handshake angle. Done with feet, wedges, printed legs, or commercial kits (see Chapter 14).

Tinning. Coating a surface with a thin layer of solder before making the real joint: you tin the iron's tip to keep it healthy, and you tin wires so they solder cleanly (see Chapter 6).

TRRS / TRS. Types of 3.5 mm audio-style plug, named for their contact segments: Tip, Ring, Ring, Sleeve. TRRS has four contacts (three separator rings) and is what connects the Lily58's halves; TRS has three contacts, looks nearly identical, and cannot carry the data line, which makes it a classic troubleshooting trap (see Chapter 13).

Solder Your Own: Building a Split Mechanical Keyboard (Lily58) from a Kit