Synaptics ClickPad reporting finger X/Y/Z position in 6-byte packets instead of relative deltas. Required to receive pass-through frames.
Bit-bang
Driving a serial protocol from software GPIO toggling instead of a hardware peripheral. QMK’s busywait PS/2 driver; slow and jittery.
Bootmagic
QMK feature: holding a designated key (here top-left) while plugging in enters the bootloader.
BOOTSEL
The button on the Pico that, held at power-up, exposes the RPI-RP2 UF2 drive.
ClickPad
A Synaptics touchpad with no separate buttons; the whole surface clicks and zones on it act as buttons. Distinct from a TouchPad with discrete buttons.
COL2ROW
QMK diode direction: current flows from column to row through the key’s diode. Determines which side is driven and which is sensed. With the shift-register chain the “column” side is the chain.
Drive line
A matrix line the firmware pulls LOW one at a time while reading the others. Rows in QMK’s default terminology.
FFC
Flat Flexible Cable — a laminated ribbon with exposed ends; used here as the 40-pin extension.
FPC
Flexible Printed Circuit — a polyimide flex with etched traces; the keyboard and ClickPad tails.
FRU
Field Replaceable Unit — Lenovo’s part number for a service part (e.g. 0C44020).
Guest / pass-through
The Synaptics mechanism that forwards a second PS/2 device’s packets (the TrackPoint) inside the touchpad’s own stream, marked by W == 3.
Magic knock
The Synaptics identify sequence: four SetResolution commands encoding a query number, then StatusRequest.
NKRO
N-Key Rollover — every key reports independently; needs the matrix diodes to avoid ghosting.
PIO
RP2040 Programmable I/O — small state machines that implement protocols in hardware. QMK’s vendor PS/2 driver runs on PIO0.
PL / CP / Q7 / DS / CE
74HC165 pins: parallel load, clock, serial out, serial in, clock enable.
PS/2
The two-wire (CLK, DATA) bidirectional serial bus used by the ClickPad and TrackPoint.
Rev A / Rev B
Perfboard build / KiCad PCB build. Same firmware, same GPIO map.
Sense line
A matrix line read (with a pull-up) while a drive line is LOW. Read through the 74HC165 chain.
SIP network
Single-in-line resistor network; “bussed” means all resistors share one common pin.
TrackPoint
The red pointing stick; strain gauges plus a controller that outputs PS/2.
UF2
USB Flashing Format — the file you drag onto the RPI-RP2 drive.
ZIF
Zero Insertion Force connector — a hinged tab clamps the FPC after insertion.