7
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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
n
Parity: even
n
Baud rate (bps): 57600 (factory setting)
Example: Reading out measured values
Instruction:
a) Set the communication parameters (see above) 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
n
1 = weak signal
n
2 = critical signal
201
1
uint16_t
n
Bit 0: switching output:
▪ 0 = Inactive
▪ 1 = Active
n
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]