min_ticks 6 broke 5 percent striking - seven current segments where 3 gave
eight, on a 36.5 s fire window against 41.4 s for eight rungs. Below the
minimum the model emits min ticks every min/on periods, so the interval
between pulses is min_ticks x tick / density and the base period cancels,
which is also why periods 10, 20 and 40 gave identical results earlier.
At 5 percent that is 2.26 ms at min 3, which struck, against 4.51 ms at 6,
which did not: doubling the minimum doubles the gap as well as the pulse,
and the discharge is re-struck each pulse.
min 3 sits at the factory's own operating point - its 6.5 percent engrave
jobs place 100 us pulses 1.54 ms apart against 1.64 ms for min 3 at that
density - and 6 is outside anything the factory does. The bench is back
at 3.
Measured band for this tube: strikes from ~5 percent density, marks from
~10 percent at F300. That closes the pulse-structure route to a usable
1 percent, since the interval grows as 1/density and 1 percent implies an
11 ms gap. The low end is a scaling problem, and $35 is the control.
The fifth ladder, the first with a minimum pulse, moved the floor down a
full rung: only 5 percent failed to mark, and 5 percent now strikes. The
trace carries eight current segments where the run before it had seven,
with fire beginning at 6.2 s exactly at rung 1 and the usual flat
saturated final segment anchoring the count from the other end.
That retracts what the previous entry concluded. Pulse length is not
irrelevant: 10 percent moved from no mark at F100, with three times the
dose per millimeter, to a mark at F300 at the same density, the only
change being its pulses growing from 36-71 us stubs to 106 us. The
matched-pairs argument was sound but drawn entirely from comparisons at
or above 20 percent density, where every pulse length in play was already
long enough - it generalized from the one regime where pulse length does
not bite. Above ~100 us dose governs; below it pulse length does; below
~36 us the supply does not strike. The factory's 100 us quantum sits on
that boundary.
dladder now reads laser_pulse_min_ticks and prints what is actually
emitted. Without that its table reports the pulse density alone would
give, which is wrong wherever the minimum applies - at min 6 the bottom
four rungs all emit 213 us and vary their rate instead, and the operator
reads that table to interpret the material.
Rule 15 in the stream harness holds both halves of the minimum
(grblHAL-glowforge f7e8c17, pinned here): no emitted burst falls below
laser_pulse_min_ticks, excepting one clipped by fire going off mid-burst,
and the levels too faint to fill a window still render their exact
average density. Checked against a run at minimum 1 so it cannot pass
vacuously - level 2 goes from 444 bursts of one tick to 147 of three at
the same density, and levels already above the minimum are unchanged.
Four bench ladders settle the base period at 20. The same six rungs
marked in all of them, and the matched pairs across periods separate the
variables: at identical pulse length, halving the density killed the
mark; at identical density, varying the pulse 3x changed nothing. Feed
does not move it either - 10 percent at F100 carries 44 percent more
energy per mm than 20 percent at F300, which marks, and still left
nothing. The low-end marking limit is average power, not dose per length
and not pulse length.
The F100 trace separates two failures that look alike on the material:
seven current segments for eight rungs, anchored by a flat saturated
final segment that can only be full density, put 5 percent at no
discharge at all and 10 percent at a full 15 seconds of current with no
mark. Only the first is ours, and the minimum pulse is the answer to it.
Also recorded: the factory's Precision Power 1 runs a 19.53 percent FIRE
duty cycle at full PWM duty, and its 1-100 scale maps onto density
18.9-79.5 percent, so its 1 percent is the bottom of the useful band
rather than 1 percent of the range. Under the density model $35 and $36
are that same control - a density floor and ceiling - which makes the
user-facing scale a settings choice rather than new code.
Four new sessions in the stream harness cover the model (grblHAL-glowforge
2bca017, pinned here). Density renders the commanded level exactly -
levels 2, 3, 7, 15, 25 and 38 came back as 0.0158, 0.0237, 0.0551,
0.1182, 0.1969 and 0.2993 against level/127 of 0.01575, 0.02362, 0.05512,
0.11811, 0.19685 and 0.29921 - S1000 renders 1.0000 and still ends dark,
every power byte carries full duty, and a level change inside a run costs
no stream byte where analog ships one per level.
Rule 13 is the one worth having: the same job run under both models
produces an identical motion grid tick for tick, and all 20051 density
FIRE ticks fall inside the 169776 the analog run fired. The model masks
the core's fire state and never sources one, measured rather than argued.
Rule 14 covers the idle-gap fix: a standalone S between moves, from a
sender slow enough to drain the planner, now fires each move at its own
level (28338 ticks each at duties 30, 52 and 84). Before the fix duty 30
held all 85014 and the other two levels never appeared. That closes
"Next work" item 18, which this work opened earlier today.
The harness now derives its expectations from the board's floor and
chains two launches over one settings file, because the core precomputes
the S to duty mapping once when the spindle is enabled: $35 written at
runtime persists and reports immediately but only enters force at the
next controller start. That is recorded in BRINGUP beside the existing
defaults note, and laser.power-floor's failure message now says so.
Acceptance: the density path shipping off by default is inert until
laser_power_model is set, and the laser tests' covers already name
grblhal-glowforge src/**; the model's own acceptance test waits on the
bench drill that picks the base period.
The pthresh ladder on scrap puts the tube's two thresholds far apart: the
discharge strikes between 2 and 3 percent duty, but nothing lases usefully
below 16 percent (PWMSAR 20), and the rungs between show only a spot at
each line start. $35 ships at 16 (grblhal-glowforge 9466f76, pinned here).
The drill said current lift-off and first mark share a rung; this run
falsifies that, so its docstring and read-the-material text now name both
thresholds and warn that a start-of-line spot is below the threshold, not
at it.
A start-of-line spot is also what a full-power leak at a kernel run start
would look like, so laser_stream_test gains a ladder session (rule 10):
every FIRE tick must ride a commanded duty, and the fire ticks must divide
evenly across rungs. Both hold exactly - six commanded duties, no others,
and 28296 fire ticks on every rung - so the spots are the tube, not the
stream. The harness now derives its expectations from the floor, which
moves the M4 session's S500 plateau from 63 to 73.
laser.power-floor is a new auto acceptance test, the suite's only
non-firing one: a machine must actually carry the commissioned floor,
since stored settings beat freshly baked defaults.
Three cloud cuts of one square at Precision Power 1, 100 and Full Power
show what the analog path is competing with: the power byte is pinned at
127 in all three, dose is FIRE-bit density on a fixed 7-tick period with
the on-count dithered between adjacent integers, and the power setting
never reaches the machine at all. Facts bank and item 17 carry the
numbers; CAMPAIGN-LOG carries both sessions.
The dated record for the jerky-at-2000-mm/min thread: what was wrong,
what changed, and what the bench measured.
Keeps the two results that matter. The A/B that isolated the cause -
two acceptance runs 90 s apart on one image, camera the only variable,
PASS with a nice-5 CPU hog and FAIL with the camera streaming - and the
LB-GF-OG-FM job re-run on the fix with the video live, clean at
min margin 3.1 ms of 10.
Also records that max behind is not the instrument: it reads 0.0 ms
through a passing run whose real margin fell to 4.9 ms, because the
producer never falls behind its own wakeup epoch. Only the measured
min margin shows the condition.
BRINGUP had grown to 3,122 lines in which the same subject was answered
differently depending on where the reader stopped: GATE A "stays open, no
live-fire" in the phase text and closed in the campaign record, the catalog
at 24 tests in one section and 35 in another, several "bench validation
pending" headings over bodies that recorded the pass.
Split by kind rather than by age. BRINGUP (907 lines) is the present state
only - status, bench runbook, laser, lid/interlock/button policy, homing,
forgectrl, diagnostics, logging, release acceptance, the measured facts
bank, and a Next work list of the 15 items that are actually open.
CAMPAIGN-LOG (2,657 lines) takes the dated blocks verbatim, in
chronological order, and is append-only: a correction is a later entry, not
an edit. Its two reading rules are stated up front, since moved text keeps
its original "above"/"below" and its pre-split item numbers.
Facts corrected against the tree while rewriting: the liveness probe gates
at p2p 800, not 500, with the real wedge, noise and jolt figures; the panel
has seven tabs including Logs and is built from src/ui/, not ui.c; the
devserver replaced tools/mock.py; /status reports real head presence; the
estop_halts_motion opt-in is gone; core PR #999 is merged, leaving only the
step_us_min commit fork-only; the update system stands at Phase 5, the
uSDHC pads and the 2026-08-08 kernel batch have shipped, and 8 MP camera
capture is tracked here for the first time.
SAFETY and UPDATE-SYSTEM point their drill records at the log. ACCEPTANCE
records that inheritance is local: there is no import of a published
artifact, so a second bench starts from a full campaign - one of the four
open items the retired tool plan held, the rest of which are now in
BRINGUP's acceptance item.
Documentation only, no behavior change and no catalog consequence: docs/
is outside every layer and .md is excluded from the layer content hash.
ScottW514