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docs(series4): the 2026-09-22 failure is accounted for -- the timeline was wrong

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An earlier draft said the Prolific-cable finding did not fit the timeline, since
the unit was described as working and then degrading, which a cable that never
enumerates cannot do.  The timeline was what needed correcting.

From the operator: the initial setup was ONE modem and ONE cable, and it worked.
Two Micromates then had to be deployed, so a second cable was fetched to run both
at once -- and only one of the two ever worked.  The other never talked over its
modem at any point, was never deployed, and a MiniMate Plus went out in its place.
That Micromate came back to the bench, and the cable on it is a Benfei (Prolific
PL2303).

So nothing degraded.  The "worked at first" was the single-cable setup before the
split.  One unit working and one not, configured side by side, is the signature of
a mixed cable supply rather than a unit fault.

Still worth confirming whether that cable travelled home with the unit or was
picked up at the bench; if it travelled with it there is no inference left.  The
FTDI cable arriving 2026-09-26 settles it either way -- same unit, same modem, one
variable.

Records a corollary: "just deploy a Series III instead" works partly because a
MiniMate Plus has a DB-9 port directly on the unit, with no USB-to-serial adapter
in the path and therefore no chipset to get wrong.  That workaround has been
routing around this exact failure mode.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
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serversdown
2026-09-25 23:27:21 -04:00
co-authored by Claude Opus 5
parent 4a96e1a2b2
commit 0659543a15
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@@ -2119,20 +2119,40 @@ FTDI is VID `0403`, Prolific is `067b`. Note also that counterfeit FTDI chips
are common in cheap cables — they carry FTDI's VID but may not behave like one, are common in cheap cables — they carry FTDI's VID but may not behave like one,
and an embedded host with a single driver is far less forgiving than Linux. and an embedded host with a single driver is far less forgiving than Linux.
### Does this explain the 2026-09-22 field outage? ### ✅ This accounts for the 2026-09-22 failure
⚠ **Not on the timeline as reported.** A Prolific cable does not fail An earlier draft of this section said the timeline did not fit, because the unit
*gradually* — it never enumerates, so the modem port never works at all. The was described as *working at first and then degrading* — which a Prolific cable
unit was described as working at first and degrading. cannot do, since it never enumerates at all.
There is one story where it fits: if the initial success was over a **different **The timeline was the thing that needed correcting, not the finding.** From the
path** — the USB **PC** port, or a bench test before deployment — that would work operator, 2026-09-25:
regardless of which serial cable was attached. The modem path would then have
been broken from the moment it was deployed, and "it worked and then stopped"
would be a recollection conflating two connection types days after the fact.
Plausible, unverified, and recorded as such. Identifying that unit's cable would 1. Initial setup — **one** modem, **one** cable. Worked: configs sent, status
settle it. read, no trouble.
2. Two Micromates then had to be deployed, so a **second cable** was fetched to
run both at once.
3. **Only one of the two ever worked.** The other would not talk over its modem
at any point.
4. That unit was never deployed — a **MiniMate Plus was put out in its place**,
and the Micromate came back to the bench.
5. The cable on that bench unit is a **Benfei (Prolific PL2303)**.
So nothing degraded. The "worked at first" was the original single-cable setup;
the failure began when the pair was split across two cables and one of them was
the wrong chipset. **One working and one not, set up side by side, is the
signature of a mixed cable supply** — not of a unit fault.
⚠ Still worth confirming: whether that cable travelled home *with* the unit, or
was picked up separately at the bench. If it travelled with it, there is no
inference left. Either way the FTDI cable arriving 2026-09-26 settles it — same
unit, same modem, one variable.
**Corollary worth knowing.** The standing workaround — *"just deploy a Series III
instead"* — works partly because a **MiniMate Plus has a DB-9 port directly on the
unit.** No USB-to-serial adapter anywhere in the path, so there is no chipset to
get wrong. That workaround has been quietly routing around this exact failure
mode.
### How this was isolated — the method is reusable ### How this was isolated — the method is reusable