7 | Commissioning Baumer
22 Operating Manual OM20/ OM30 RS485 with Modbus RTU | V1
7.2 Set up RS485 interface with Modbus RTU
The sensor supports Modbus RTU via RS485 for retrieving measured values and for parameter-
ization.
Communication via the RS485 interface is a serial master-slave communication, which is why
the serial communication parameters must first be known for all participants:
n
Slave address: 1 (factory setting)
n
Data bits: 8
n
Number of stop bits: 1 bit
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Parity: even
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Baud rate (bps): 57600 (factory setting)
Example: Reading out measured values
Instruction:
a) Set the communication parameters (seeabove) on the master.
b) Read the input register.
Function ID: 04
Address 200: All Measurements
Number of registers: 13
Result:
ü You receive the response telegram with the following structure (the measured value is in ad-
dress 202 and 203).
INFO
1 Modbus register corresponds to 2 bytes. If the data type of a sensor parameter is wider than a
2 byte Modbus register, the parameter is divided among several Modbus registers. The less sig-
nificant bits are located at the smaller address and the more significant bits at the larger ad-
dress (Little Endian).
Address Number of registers Data type Description
200 1 uint16_t Measured value signal quality:
n
0 = ok
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1 = weak signal
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2 = critical signal
201 1 uint16_t
n
Bit 0: switching output:
▪ 0 = Inactive
▪ 1 = Active
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Bit 1: alarm output
▪ 0 = Inactive
▪ 1 = Active
202 - 203 2 float32_t Distance [mm]
204 - 205 2 float32_t Measurement rate [Hz]
206 1 uint16_t Exposure reserve
207 - 208 2 uint32_t Response delay [µs]
209 - 210 2 uint32_t Time stamp [s]
211 - 212 2 uint32_t Time stamp [µs]
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