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1. Duty Cycle Enforcement
The sensor dynamically enforces the duty cycle itself based on the length of the data packets.
2. Payload Description
2.1. Payload Layout
Byte indices in parentheses:
- (2–3) VendorID: UInt16 BE
- (5–6) DeviceID: UInt16 BE
- (8–9) Measurement Value A: device-specific (usually UInt16/Int16 × 0.1)
- (10–11) Flags/status depending on device
- (12–13) Measurement value B: device-specific
- (15) Status nibble (lower 4 bits) — only on some devices
- All other bytes (0–1, 4, 7, 14) Reserved.
Endianness: all 16-bit words are big-endian (readUInt16BE)
2.2. Example Payload for LDH292
| Byte index(es) | Length | Field | Data type | Scale | Unit | Notes |
|---|---|---|---|---|---|---|
| 2–3 | 2 | VendorID | UInt16 BE | ×1 | – | Expected: 0x0136 (dec. 310) |
| 5–6 | 2 | DeviceID | UInt16 BE | ×1 | – | Expected: 0x0539 (dec. 1337) |
| 8–9 | 2 | Humidity | UInt16 BE | ×0.1 | %RH | e.g., raw value 553 → 55.3 %RH |
| 12–13 | 2 | Temperature | UInt16 BE | ×0.1 | °C | e.g., raw value 234 → 23.4 °C |
| 15 (low nibble) | 4 bits | DeviceStatus | Enum | – | – | bytes[15] & 0x0F |
| – | – | (not used in the code) | – | – | – | Bytes 0–1, 4, 7, 10–11, 14 appear to be reserved/unclear |
Status codes (lower 4 bits of byte 15)
| Code | Meaning |
|---|---|
| 0 | OK |
| 1 | Maintenance required |
| 2 | Out of specification |
| 3 | Functional check |
| 4 | Failure |
| Other | Unknown (Code) |
3. Example LDH292
| IDX | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 0A | 0B | 0C | 0D | 0E | 0F |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| HEX | 00 | 00 | 01 | 36 | 00 | 05 | 39 | 00 | 02 | 29 | 00 | 00 | 00 | EA | 00 | 00 |
- Idx 2–3 → VendorID: 0x01 0x36 → 0x0136 → decimal 310
- Idx 5–6 → DeviceID: 0x05 0x39 → 0x0539 → decimal 1337
- Idx 8–9 → Humidity: 0x02 0x29 → 0x0229 → 553 × 0.1 → 55.3 %RH
- Idx 12–13 → Temperature: 0x00 0xEA → 234 × 0.1 → 23.4 °C
- Idx 15 → Status byte: 0x00; low nibble = 0x00 & 0x0F → 0 (OK)
