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Phase 3 PR 46 -- DL205 BCD decoder #45

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dohertj2 merged 1 commits from phase-3-pr46-dl205-bcd into v2 2026-04-18 22:13:26 -04:00
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dohertj2 commented 2026-04-18 22:13:21 -04:00
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Summary

Stacked on PR 45. Adds ModbusDataType.Bcd16 + Bcd32 for DirectLOGIC binary-coded-decimal numerics.

  • DL205/DL260 store timers/counters/operator-display values as BCD (register 0x1234 = decimal 1234, NOT 4660).
  • DecodeBcd walks nibbles MSB→LSB; rejects any nibble > 9 with InvalidDataException (prevents silent data corruption on transient garbage).
  • Bcd32 respects ModbusByteOrder so word-swap families can use it.
  • Caller must opt in per tag; default decoding stays binary.

Validation

  • 66/66 Modbus.Tests pass (including Bcd16_decodes_DL205_register_1234_as_decimal_1234 with control vs Int16)
  • 3/3 DL205 integration tests pass (HR[1072]=0x1234 decodes 1234 under BCD, 0x1234 under Int16)

Test plan

  • Nibble overflow detection
  • Encode/decode round-trip (both widths)
  • Word-swap for BCD32
  • Integration test against pymodbus dl205 profile
## Summary Stacked on PR 45. Adds `ModbusDataType.Bcd16` + `Bcd32` for DirectLOGIC binary-coded-decimal numerics. - DL205/DL260 store timers/counters/operator-display values as BCD (register `0x1234` = decimal 1234, NOT 4660). - `DecodeBcd` walks nibbles MSB→LSB; rejects any nibble > 9 with `InvalidDataException` (prevents silent data corruption on transient garbage). - `Bcd32` respects `ModbusByteOrder` so word-swap families can use it. - Caller must opt in per tag; default decoding stays binary. ## Validation - 66/66 Modbus.Tests pass (including `Bcd16_decodes_DL205_register_1234_as_decimal_1234` with control vs Int16) - 3/3 DL205 integration tests pass (HR[1072]=0x1234 decodes 1234 under BCD, 0x1234 under Int16) ## Test plan - [x] Nibble overflow detection - [x] Encode/decode round-trip (both widths) - [x] Word-swap for BCD32 - [x] Integration test against pymodbus dl205 profile
dohertj2 added 1 commit 2026-04-18 22:13:22 -04:00
Phase 3 PR 46 -- DL205 BCD decoder (binary-coded-decimal numeric encoding). Adds ModbusDataType.Bcd16 and Bcd32 to the driver. Bcd16 is 1 register wide, Bcd32 is 2 registers wide; Bcd32 respects ModbusByteOrder (BigEndian/WordSwap) the same way Int32 does so the CDAB-style families (including DL205/DL260 themselves) can be configured. DecodeRegister uses the new internal DecodeBcd helper: walks each nibble from MSB to LSB, multiplies the running result by 10, adds the nibble as a decimal digit. Explicitly rejects nibbles > 9 with InvalidDataException -- hardware sometimes produces garbage during write-in-progress transitions and silently returning wrong numeric values would quietly corrupt the caller's data. EncodeRegister's new EncodeBcd inverts the operation (mod/div by 10 nibble-by-nibble) with an up-front overflow check against 10^nibbles-1. Why this matters for DL205/DL260: AutomationDirect DirectLOGIC uses BCD as the default numeric encoding for timers, counters, and operator-display numerics (not binary). A plain Int16 read of register 0x1234 returns 4660; the BCD path returns 1234. The two differ enough that silently defaulting to Int16 would give wildly wrong HMI values -- the caller must opt in to Bcd16/Bcd32 per tag. Unit tests: DecodeBcd (theory: 0,1,9,10,1234,9999), DecodeBcd_rejects_nibbles_above_nine, EncodeBcd (theory), Bcd16_decodes_DL205_register_1234_as_decimal_1234 (control: same bytes as Int16 decode to 4660), Bcd16_encode_round_trips_with_decode, Bcd16_encode_rejects_out_of_range_values, Bcd32_decodes_8_digits_big_endian, Bcd32_word_swap_handles_CDAB_layout, Bcd32_encode_round_trips_with_decode, Bcd_RegisterCount_matches_underlying_width. 66/66 Modbus.Tests pass. Integration test: DL205BcdQuirkTests.DL205_BCD16_decodes_HR1072_as_decimal_1234 against dl205.json pymodbus profile (HR[1072]=0x1234). Asserts Bcd16 decode=1234 AND Int16 decode=0x1234 on the same wire bytes to prove the paths are distinct. 3/3 DL205 integration tests pass with MODBUS_SIM_PROFILE=dl205. 8248b126ce
dohertj2 merged commit 1a60470d4a into v2 2026-04-18 22:13:26 -04:00
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Reference: dohertj2/lmxopcua#45
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