ModbusSimulatorFixture default port bumped from 502 to 5020 to match the pymodbus convention. Override via MODBUS_SIM_ENDPOINT for a real PLC on its native 502. Skip-message updated to point at the new Pymodbus\serve.ps1 wrapper instead of 'start ModbusPal'. csproj <None Update> rule swapped from ModbusPal/** to Pymodbus/** so the new JSON profiles + serve.ps1 + README copy to test-output as PreserveNewest.
standard.json — generic Modbus TCP server, slave id 1, port 5020, shared blocks=false (independent coils + HR address spaces, more textbook-PLC-like). HR[0..31] seeded with address-as-value via per-register uint16 entries, HR[100] auto-increments via the built-in increment action with parameters minval=0/maxval=65535 (drives subscribe-and-receive integration tests so they have a register that ticks without a write — pymodbus's increment ticks per-access not wall-clock, which is good enough for a 250ms-poll test), HR[200..209] scratch range left at 0 for write tests, coils 0..31 alternating, coils 100..109 scratch. write list covers 0..1023 so any test address is mutable.
dl205.json — AutomationDirect DirectLOGIC DL205/DL260 quirk simulator, slave id 1, port 5020, shared blocks=true (matches DL series memory model where coils/DI/HR overlay the same word address space). Each quirky register seeded with the pre-computed raw uint16 value documented in docs/v2/dl205.md, with an inline _quirk JSON-comment naming the behavior so future-me reading the file knows why HR[1040]=25928 means 'H' lo / 'e' hi (the user's headline string-byte-order finding). Encoded quirks: V0 marker at HR[0]=0xCAFE; V2000 at HR[1024]=0x2000; V40400 at HR[8448]=0x4040; 'Hello' string at HR[1040..1042] first-char-low-byte; Float32 1.5f at HR[1056..1057] in CDAB word order (low word first); BCD register at HR[1072]=0x1234; FC03-128-cap block at HR[1280..1407]; Y0/C0 coil markers at 2048/3072; scratch C-relays at 4000..4007.
serve.ps1 wrapper — pwsh script with a -Profile {standard|dl205} parameter switch. Validates pymodbus.simulator is on PATH (clearer message than the raw CommandNotFoundException), validates the profile JSON exists, builds the right --modbus_server/--modbus_device/--json_file/--http_port arg list, and execs pymodbus.simulator in the foreground. -HttpPort 0 disables the web UI. Foreground exec lets the operator Ctrl+C to stop without an extra control script.
README.md fully rewritten for pymodbus: install command (pip install 'pymodbus[simulator]==3.13.0' — pinned for reproducibility, [simulator] extra pulls aiohttp), per-profile reference tables, the same DL205 quirk → register table from PR 42 but adjusted for pymodbus paths, what's-NEW-vs-ModbusPal section (all four tables, raw uint16 seeding, declarative actions, custom Python action modules, headless, web UI, maintained), trade-offs section (float32-as-two-uint16s for explicit CDAB control, increment ticks per-access not wall-clock, shared-blocks mode for DL205 vs separate for Standard), file-format quick reference for hand-authoring more profiles. References pinned to the pymodbus readthedocs simulator/config + REST API pages.
docs/v2/modbus-test-plan.md harness section rewritten with the swap rationale; PR-history list updated to mark PR 42 SUPERSEDED by PR 43 and call out PR 44+ as the per-quirk implementation track. Test-conventions bullet about 'don't depend on ModbusPal state between tests' generalized to 'don't depend on simulator state' and a note added that pymodbus's REST API can reset state between facts if a test ever needs it.
DL205Profile.cs and DL205SmokeTests.cs xml-doc updated to reference pymodbus / dl205.json instead of ModbusPal / DL205.xmpp.
Functional validation deferred — Python isn't installed on this dev box (winget search returned no matches for Python.Python.3 exact). JSON parses structurally (PowerShell ConvertFrom-Json clean on both files), build clean, .json + serve.ps1 + README all copy to test-output as expected. User installs pymodbus when they want to actually run the simulator end-to-end; if pymodbus rejects the config the README's reference link to pymodbus's simulator/config schema doc is the right next stop.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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