kernel.pic-pacing drill; BRINGUP item 10 and the record

kernel.pic-pacing reads a coolant thermistor twice back to back, 300
pairs, with the module's pacing off (the control, reported) and on (the
claim: the second read agrees with the first). The bench proof for the
module's pic_gap_us pacing; the catalog counts 56 tests, 0 uncovered.

BRINGUP item 10 and the facts bullet describe the pacing as it is; the
CAMPAIGN-LOG entry records the change and its proof.
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ScottW514
2026-09-02 20:30:41 -04:00
parent 1f2c795d8c
commit 358c287891
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@@ -1005,18 +1005,17 @@ is committed.
within seconds and inflates the instant reading by a degree; the warm-up
release therefore judges a one-minute rolling minimum of that reading.
- **Coolant-ADC readings depend on the read pattern.** What the PIC returns
for a thermistor depends on how soon the read follows the previous PIC read
(measured 2026-09-02 on the two coolant channels): the second of a pair
issued within 0.1 ms comes back 6 to 8 counts high with a wide spread,
either sensor, either order; a pair 0.5 to 10 ms apart reads tight and a
steady 3 counts (about 0.2 C) above sparse reads; and concurrent readers
land such pairs at random, so a fast reader sees excursions of 10 to 15
counts in a share of its samples that grows with the read rate (a third at
100 Hz). The `aa-offset-calibrate` diagnostic reads its two sensors 31 ms
apart and reduces each window to an interquartile mean; the cooling engine
and `/status` still read the PIC back to back (the bias is inside the
gates' margins). A pacing of PIC reads in the kernel would give every reader
the same value (Next work).
for a thermistor depends on how soon the read follows the previous PIC
transaction (measured 2026-09-02 on the two coolant channels): the second
of a pair issued within 0.1 ms comes back 6 to 8 counts high with a wide
spread, either sensor, either order; a pair 0.5 to 10 ms apart reads tight
and a steady 3 counts (about 0.2 C) above sparse reads. The module paces
every PIC transaction (`pic_gap_us`, 1000 by default, a runtime-writable
parameter), so no reader lands a disturbed pair whatever the others do;
the `aa-offset-calibrate` diagnostic still reads its two sensors 31 ms
apart and reduces each window to an interquartile mean, which takes the
steady bias out of its edges. `kernel.pic-pacing` measures the pairs with
the pacing off and on.
- **Coolant-ADC offsets around a lit tube.** The air-assist fan's return
current rides a ground path the thermistor reference shares, so both coolant
sensors read about 1.2 C low at the run duty (proportional to the fan's
@@ -1388,14 +1387,16 @@ feature requests, enhancements) will eventually be tracked as GitHub issues.
live-fire drill is gone; a coolant sensor unreadable for two ticks is the
SENSOR verdict.
10. **PIC read pacing.** A PIC read within a fraction of a millisecond of
the previous one returns a disturbed value (facts bank, "Coolant-ADC
readings depend on the read pattern"). Serialize the PIC transactions in
the kernel module with a minimum spacing (a millisecond is enough by the
measurement), so every reader, the engine, `/status`, the diagnostics and
a bench sampler, sees the same value whatever the others do. A module
change: it rides the next image flash, with the coolant-reading tests
(`cooling.aa-offset-calibrate`, `cooling.flow-verify`) as its proof.
10. **PIC read pacing, done and waiting for the image.** The module paces
every PIC transaction at least `pic_gap_us` (1000, a runtime-writable
parameter) after the last one ended, so every reader, the engine,
`/status`, the diagnostics and a bench sampler, sees the same value
whatever the others do (facts bank, "Coolant-ADC readings depend on the
read pattern"). Host-proven by the module's -Werror cross-build; on the
bench, the new `kernel.pic-pacing` drill (300 back-to-back pairs with the
pacing off, then on) and the coolant-reading tests
(`cooling.aa-offset-calibrate`, `cooling.flow-verify`). Rides item 9's
image; the item closes with the campaign.
11. **The audit's deferred findings, done and waiting for the image.** All six
are fixed and host-proven, and ride the local image item 9's campaign