Modbus¶
MODBUS communication protocol¶
| Important: Please read out the MODBUS byte order of the RMS device with RMS-CONFIG prior to any programming. |
|---|
For direct connection to other systems, the device provides a MODBUS TCP server. To following data is available via MODBUS communication:
| Protocol | MODBUS TCP |
|---|---|
| TCP Port | 502 |
When reading out data from the input register select the index=-1.¶
Function 04- Read Input Register¶
| 30001 | Serial number | Unsigned 32 Bit | |
|---|---|---|---|
| 30002 | |||
| 30003 | Serial number of the probe | Unsigned 32 Bit | |
| 30004 |
| 31001 | Value 1 | Measurement value 1 of the sensor | Float 32 Bit |
|---|---|---|---|
| 31002 | |||
| 31003 | Value 2 | Measurement value 2 of the sensor | Float 32 Bit |
| 31004 |
The measurement values are only available in floating format.
Swap mode¶
The swap mode defines how a float32 value is represented in MODBUS data structure. The settings must be done with the RMS-CONFIG software.
Factory settings: WORD-Swap
Example:
| Value 1 (Address 31001 / 31002) | 45.0 = 0x42340000 |
|---|---|
| Value 2 (Address 31001 / 31002) | 1000.0 = 0x447A0000 |
The following website helps for conversion: https://www.h-schmidt.net/FloatConverter/IEEE754de.html
The RMS LAN devices (except the RMS-Converter) are based on a Little Endian memory organisation (The device firmware provides the MODBUS information starting with the most significant byte.)
| 31001 | 0 | 0x0000 | 31001 | 13378 | 0x3442 |
|---|---|---|---|---|---|
| 31002 | 13378 | 0x3442 | 31002 | 0 | 0x0000 |
| 31003 | 0 | 0x0000 | 31003 | 31300 | 0x7A44 |
| 31004 | 31300 | 0x7A44 | 31004 | 0 | 0x0000 |
| Byte Swap (Mixed Endian) | Byte and Word Swap (Big Endian) | ||||
| 31001 | 0 | 0x0000 | 31001 | 16948 | 0x4234 |
| 31002 | 16948 | 0x4234 | 31002 | 0 | 0x0000 |
| 31003 | 0 | 0x0000 | 31003 | 17530 | 0x447A |
| 31004 | 17530 | 0x447A | 31004 | 0 | 0x0000 |
Software Compatibility¶
The logger is designed for use with the RMS server software (local installation or Rotronic Cloud). The data logger can alternatively also be operated with the RMS-Configuration software (standalone software).
Connection timeout: When TCP connection is open and for more than 30 seconds no communication is performed, the device automatically closes the TCP connection. In case of a communication interruption, this prevents the socket being blocked.
Additional MODBUS details can be found here: MODBUS in RMS.
Updated: 13.12.2023.