Modbus communication examples - INDIGO500SERIES - INDIGO510 - INDIGO520

Indigo510, Indigo520 User Guide

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Document type
User guide

Reading RH value from HMP4 probe connected to the transmitter as Probe 1

The values returned by the device differ depending on the ambient conditions. Your device might not return exactly the same values.
Request Response
Bytes in the frame (hexadecimal) Description Bytes in the frame (hexadecimal) Description
00hex Transaction ID 00hex Transaction ID
01hex 01hex
00hex Protocol ID 00hex Protocol ID
00hex 00hex
00hex Length (6) 00hex Length (7)
06hex 07hex
F1hex Unit ID (probe 1) F1hex Unit ID (probe 1)
03hex Function (Read Holding Registers) 03hex Function (Read Holding Registers)
00hex Register address 04hex Number of data bytes
00hex 7Ahex Value of first register (least significant word)
00hex Number of 16-bit registers to read (2) E1hex
02hex 41hex Value of second register (most significant word)
Communication description
Transaction identifier Any number identifying the response and the corresponding request on a Modbus TCP/IP transaction
Protocol identifier 0 (Modbus Protocol) as specified for Modbus TCP/IP
Length Number of remaining bytes in the frame starting from the unit ID
Register number 1 (1-based Modbus register number) = 0000hex (0-based register address used in actual communication) based on the Modbus reference in HMP Series with MMP8 and TMP1 User Guide (M212022EN)
Data format Two 16-bit Modbus registers interpreted as IEEE 754 binary32 floating point value, least significant word first
Returned value 41F47AE1hex, which is binary32 representation of 30.56 (%RH)