[BioCam]

The Problem

Every motion on the Mantis runs through its sequencer: a queue on the motion board that plays valve states and moves in order, each held for a set time. The device also reports, unasked, when a motor starts, finishes, homes or faults, and when a queued item plays. Without a sequencer and without reading those reports, nothing can move safely: a wait cannot know its move finished, and a motor fault goes unnoticed.

PR Content/Solution

• Events (driver/events.py): every report the device sends unasked is decoded by its content (motion started, move done, home done, motor error, sequence progress, sequencer stopped, input changed) and logged in words; an unknown one is logged by its number. A motor-error report fails every waiting motion at once.
• Sequencer: clear, start, stop, abort and queueing a valve write (_queue_ppi_write), each sent once. A full queue (200 items) answers -1; the write is sent again under the next item number until it is queued, for at most default_queue_full_timeout (60 s), so no item can play twice. A wait for an item does not miss a report that arrived with the reply.
• Simulation: a 200-item queue that plays at once when started.

This is the base the arm and pump PRs queue through; it has no user-facing call of its own beyond default_queue_full_timeout.

On the device

A Mantis v4 on Windows (D2XX); only the chip valves switched, the pump stayed off:

	result
queue depth, not started	200: free 199 down to 0, then -1; the slots come back after a clear
a queue write sent twice under one packet number	queued twice, so a queue write is never resent
hold time	1 ms per step: a hold of 500 played after 508-513 ms, ~20 ms of it the round trip
stop while running	the queue plays out, then the device reports it stopped
abort while running	stops after the current item; the rest stays queued and plays at the next start. Only a clear drops items, and a clear does not stop a running sequencer
stop or abort while idle	the queue is kept, no report
queue stays full / item never reported	MantisTimeoutError after the set time; every retry under a new item
out-of-range arguments	ValueError, nothing sent

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