Safety¶

alicatlib drives physical hardware. Safety rules are binding; see the Design doc §5.20 for the authoritative list.

Destructive operations require confirm=True¶

Commands that can damage equipment, lose data, or desync the serial link raise AlicatValidationError before any I/O if confirm is not True. Examples:

• Factory restore
• Baud change
• Unit-ID change
• Valve exhaust, valve-hold-closed
• Overpressure disable
• Power-up setpoint
• Gas-mix deletion

Setpoint validation¶

FlowController.setpoint(value, unit) checks value against the device's full-scale range (cached at session startup). Out-of-range requests raise AlicatValidationError before I/O.

V1_V7 / pre-9v00 V8_V9 / GP caveat¶

On firmware families without the LSS command, the library cannot probe the setpoint source. If the device's front-panel source is configured to Analog or User-knob rather than Serial, a dev.setpoint(value) call reaches the wire cleanly but the device silently ignores it — the setpoint follows the analog input instead. The library returns a valid SetpointState built from the post-op data frame, but that frame will reflect the actual setpoint (driven by analog), not the commanded one.

Users on these firmware families must configure the setpoint source to Serial via the front panel before opening the device. The library cannot verify this remotely.

Display lock recovery¶

dev.unlock_display() is intentionally NOT gated on Capability.DISPLAY — it is the safety escape for a locked device. Always callable.

On V1_V7 firmware, the device parses any command starting with AL<X> (e.g. ALS, ALSS, ALV) as "lock display with argument X" and sets the LCK status bit. The library's firmware gates protect these tokens under normal facade use (they never reach V1_V7 hardware), but third-party code or direct session.execute(...) can still trip it. Call dev.unlock_display() to recover.

Tare preconditions¶

Tare commands assume the device is in the correct physical state (no flow for flow tare, line depressurized for pressure tare). These are user responsibilities; the library documents them in docstrings but cannot verify them.

Hardware test tiers¶