Modbus Frames

Field gateways POST decoded Modbus RTU frames to the endpoint below using an API key. Device ID, function code, address, register values, and CRC are decoded and shown live.

/api/public/modbus

Stored locally in this browser for quick test sends.

Frame format & curl examples

Modbus RTU request layout:

01 03 04 80 00 02 45 0C

Device ID · Function · Address · #Regs · CRC

POST request + response (recommended):

curl -X POST /api/public/modbus \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_MODBUS_API_KEY" \
  -d '{"request":"01 03 04 80 00 02 45 0C","response":"01 03 04 00 7B 01 F4 BA 8A"}'

Request-only (no meter response yet):

curl -X POST /api/public/modbus \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_MODBUS_API_KEY" \
  -d '{"request":"01 03 04 80 00 28 45 0C"}'

Hex can use spaces, no spaces, commas, or 0x prefixes. Frames must be valid hex; CRC is auto-checked.

Device discovery

Scan IDs 1–10 to auto-find meters on the bus. After scanning, only verified IDs are polled.

Probe template (8-byte Modbus frame — device ID byte will be replaced 1→255, CRC recomputed)

FC=3 · address=4000 (0x0FA0) · count=4

Scan progress

0 / —

Pending IDs

Found devices

Active in queue

No devices discovered yet. Run a scan to populate this list.

Time	Device	Function	Address	#Reg	Status	Preview
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