docs(series4): soften the cable finding -- well-supported, not proven

The operator pushed back on calling this solved, correctly.  Adjusting the wording
to match what the evidence actually carries.

What IS supported: on this bench setup, the modem and cable work bidirectionally
(laptop round trip, 700 ms), the same cable/modem pairing answers for a laptop and
not for the Micromate, and neither firmware image contains a Prolific driver.
Observation plus mechanism.

What is NOT: that this explains the field failures.  Those cables cannot be
inspected, and the timeline does not fit -- a wrong cable fails from the first
packet, and that unit reportedly worked before degrading.

A gap in the bench claim itself, now stated: "no driver" is inferred from ABSENCE
of strings.  usbHostDelete_* reads like a complete per-class list, which is good
evidence, but driver code can exist without a matching string and the USB
enumeration path has not been disassembled.

Names the test that removes the inference entirely: try an FTDI cable (VID 0403)
on the same modem.  Either it works or it does not.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
This commit is contained in:
2026-09-25 20:35:13 -04:00
co-authored by Claude Opus 5
parent 84ca10eb3c
commit 8a0134070b
+13 -3
View File
@@ -2086,10 +2086,20 @@ usbHostDelete_HUB / HC / USBH
strings in each, and **zero** matches for `prolific`, `pl2303`, `cp210`, `ch34` strings in each, and **zero** matches for `prolific`, `pl2303`, `cp210`, `ch34`
or `silabs` in either. The firmware line makes no difference here. or `silabs` in either. The firmware line makes no difference here.
⚠ **So a Prolific PL2303 cable (VID `067b`) cannot work with a Micromate.** The ⚠ **So a Prolific PL2303 cable (VID `067b`) very probably cannot work with a
unit has no driver, never enumerates the device, and the serial path simply does Micromate** — no driver, so the device never enumerates and the serial path does
not exist. Use an **FTDI** cable (VID `0403`) or a CDC-ACM one. not exist. Use an **FTDI** cable (VID `0403`) or a CDC-ACM one.
**Calibration.** This rests on *absence of strings*, plus the observation that a
laptop answers on the same cable where the unit does not. `usbHostDelete_*` reads
like a complete per-class list, which is good evidence — but driver code can exist
without a matching string, and the USB enumeration path has not been
disassembled.
**The test that would remove the inference: try an FTDI cable on the same modem.**
Either it works or it does not, and nothing is left to argue about. Until then
this is well-supported, not proven.
### How this was isolated — the method is reusable ### How this was isolated — the method is reusable
A Micromate on an RX55 was unreachable from THOR. Rather than guess, each layer A Micromate on an RX55 was unreachable from THOR. Rather than guess, each layer
@@ -2116,7 +2126,7 @@ device with something known-good and re-run the same test.** It converts "the
unit is not answering" into "the unit is not receiving", which are very unit is not answering" into "the unit is not receiving", which are very
different problems. different problems.
⚠ This explains the **bench** setup conclusively. Whether it explains the ⚠ This is the best explanation for the **bench** setup. Whether it explains the
2026-09-22 field outage is **not** established — that unit reportedly worked at 2026-09-22 field outage is **not** established — that unit reportedly worked at
first and degraded, which a wrong cable would not do. Treat them as separate first and degraded, which a wrong cable would not do. Treat them as separate
until the field unit's cable is identified. until the field unit's cable is identified.