The cable swap alone did not fix it. A probe immediately after fitting a genuine
FTDI cable (lsusb 0403:6001, FT232) returned the same "connected, no reply".
A COLD BOOT of the unit was also required -- power button held five seconds
through the two-stage battery-disconnect prompt, powered back up with the cable
already attached. THOR connected the moment it finished booting, and an
independent probe returned UM12947, idle, over cellular.
So the Micromate's USB host does not rescan on hot-swap: it enumerates that port
at boot and, having once failed to identify a device, does not try again.
Changing the cable is a power-cycle operation -- and anyone swapping one in the
field who probes immediately will conclude the new cable is faulty too. Full
chain: an FTDI or CDC-ACM cable, AND a cold boot with it attached.
SEPARATELY CONFIRMED, by accident: these modems bridge ONE TCP session to serial
at a time. With THOR connected, the probe got "TCP ok, NO REPLY"; with THOR
disconnected and nothing else changed, the same probe returned the serial number.
The PAD accepts a second connection and then never forwards it -- it does not
refuse and does not close.
That makes "connected but no reply" ambiguous between a broken serial path and
somebody else already holding the unit, and mm_probe reported only the former --
which would push a diagnosis in exactly the wrong direction, on the very fault we
spent two days chasing. Its verdict now names both causes, tells you to
eliminate contention first, and includes the cable-chipset and cold-boot steps.
Recorded as an SFM design constraint: our receiver and THOR cannot both hold a
unit, and during any migration both will exist. "Another client holds this unit"
has to be a distinct visible state.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
serversdownandClaude Opus 5
a7631a8179