Feat: PRT3 ASCII serial support

[NaanyaBiz]

Discussion: PRT3 ASCII serial support

Hi all — I've been working on adding PRT3 printer module support to PAI and wanted to share it here before opening a formal PR. Happy to discuss the approach and incorporate feedback.

Why PRT3?

Two trends have progressively closed off the existing integration paths for Paradox panels:

Native serial encryption — newer EVO/Spectra firmware versions encrypt the binary serial protocol. PAI's native serial backend depends on knowledge of internal EEPROM addresses and binary framing that has been reverse-engineered over time. On affected firmware, this integration breaks or becomes unreliable.

IP150 lockdown — recent IP150 firmware restricts third-party connections. A number of users have found their IP-based integrations stop working after a panel firmware update.

The PRT3 is a different story. Paradox publishes and maintains its ASCII protocol spec which I've used as part of building this interface. It works over a commodity USB-to-serial adapter, uses no encryption, and hasn't changed in any meaningful way across firmware generations. For panels where the native protocol and IP module are no longer accessible, PRT3 is a practical, long-term integration path — and right now there's no way to use it with PAI.

What I've built

Full PRT3 support as a peer connection type:

• ASCII serial transport (line-framed on \r)
• COMM&ok handshake and reconnect handling
• Area and zone status polling (RA/RZ) with async event updates
• Label loading for areas, zones, and users (AL/ZL/UL)
• Arm / quick-arm / disarm (AA/AQ/AD)
• Panic commands (PE/PM/PF)
• Utility key commands (UK) — exposed as HA button entities via MQTT discovery
• Full event map for PRT3 G-group system events including exit/entry delay state
• MQTT and Home Assistant autodiscovery (alarm_control_panel, binary_sensor, button)
• Test suite: parser, encoder, adapter, panel, command dispatch, MQTT integration

Architecture

I was careful to keep this clean. PRT3 is wired into paradox.py's connection selection as a plain elif alongside Serial and IP. PRT3Panel extends the same base class as EVO/Spectra panels. The MQTT/HA layer is generic — no PRT3 branches in zone/partition logic.

There's one general bug fix included that isn't PRT3-specific: mqtt/core.py now fires on_connect for interfaces that register after the broker connection is already established (fixes a race where control subscriptions were never set up if MQTT connected before an interface registered).

Limitations (v1)

• Zone bypass/force not available (no PRT3 command)
• Virtual PGM outputs are not controllable
• No SetTimeDate — SYNC_TIME is a no-op
• Area count must be set in config (panel doesn't report it)
• Utility keys are not idempotent — no retries to avoid double-triggering

PR

Branch: feature/prt3-connection

Happy to squash, rebase onto dev, or restructure commits however you prefer before merge. Feedback welcome on anything — especially the paradox.py integration points and the MQTT entity approach for utility keys.

[yozik04]

@NaanyaBiz Great contribution, thank you! Will look at it in a near term.
BTW: Serial encryption needs to be tested, there is a PR for that in the repo.

[NaanyaBiz]

No problem - i have the prt3 interface up and running -- each zone entity is working reliably as are the utility keys. there were some race condition issues on the margins of timeouts (500ms) which would cause a UK to fire twice; but i fixed that bug in the last iteration and now it seems to work clean. I'll leave it with you, message me if you have queries.

[fabianogervasi-cyber]

Hi All,
I just reached the same conclusion...
Have A Paradox EVOHD with both IP150+ and PRT3 attached to a Hsyco Domotic.
I am moving to Home automation and integrate all KNX devices of the house.
Unfortunately, the IP150+ doesnot allow PAI connection (nor WEB access) any longer...PRT3, instead, is stable with my Hsyco server....
I can test your code but beeing a noobi, I don t lnow where to find it....any help welcome....if the project is still on track of course
Best,
F

[yozik04]

It is in development release already. Use that.

[fabianogervasi-cyber]

Sorry...real noobie here...could not find it in HACS?

[yozik04]

https://github.com/ParadoxAlarmInterface/pai/wiki/Home-Assistant
Read the wiki it has everything you need.

[yozik04]

Some configuration is in this PR:
#596
I won't be able to support you with basic configuration steps. Ask AI =)

[fabianogervasi-cyber]

ok. Thanks