1. MQTT / meter settings
12 decimal digits. DL/T 645 transmits address bytes low-byte first.
Automatically generated as a unique 16-digit timestamp-style ID for every encoded command.
Default: /v1/device/{meter}; command topic is /cmd, response is /response.
2. Function
Generated MQTT command
Publish topic
Choose a function and click Encode payload.
Raw message
Frame details
Paste response or raw frame
The decoder strips spaces and FE wake bytes, validates the frame checksum, subtracts 0x33 from every DATA byte, and recognizes supported identifiers.
Decoded result
Paste periodic MQTT telemetry JSON
Telemetry fields
Supported functions
| Function | Control / DI | Input handling |
|---|---|---|
| Read any data item | C=11, user DI | 4-byte DI entered as DI3..DI0; encoder transmits DI0..DI3 and adds 33H. |
| Generic write | C=14, user DI | Password authority + 3 password bytes, 4 operator bytes, raw DATA. |
| MQTT relay shortcut | message=relayon / relayoff | No 645 frame; sent exactly as documented by the MQTT layer. |
| 645 relay control | C=1C | Password/operator bytes + N1 command + reserved N2 + N3..N8 validity bytes. |
| Amount initialization | C=03, 070103FF | Operator 11223344, preset amount as 32-bit cents, fixed MAC / purchase-count fields. |
| Sales order | C=03, 070102FF | Amount as 32-bit cents; order no. exactly 8 bytes; meter/table number 6 BCD bytes. |
| Return order | C=03, 070108FF | Same field structure as sales order, per document. |
| Parameter 1 | C=03, 070104FF | All documented fixed-width fields are exposed. Because the document does not state decimal scaling for every parameter, exact raw unshifted bytes are accepted per field. |
| Parameter 2 | C=03, 070105FF | 116-byte DATA builder matching the supplied example (L=0x74): DI + operator + four 3-byte zone entries + four schedules of 8×3-byte sessions. |
| Extended meter snapshot | C=11, 028011FF | Decodes the documented 65-byte aggregate response and status word. |
Important encoding rules
645 DATA bytes are encoded by adding 0x33 before transmission and decoded by subtracting 0x33. The checksum is the modulo-256 sum from the first 68 through the final DATA byte. The 6-byte address is BCD and transmitted low-byte first.