Siemens SIMATIC S7

Connect to Siemens SIMATIC S7 PLCs using S7 Communication Services.

The SIMATIC S7 is a product line of PLCs (S7-200, S7-300, S7-400, S7-1200, S7-1500) by Siemens widely used in industrial automation. S7 PLCs connect multiple sensors and actuators through digital or analog I/Os with modular extension capabilities.

S7 PLCs are configured and programmed using STEP 7 (TIA Portal) software from Siemens.

Read and write access to PLC data is realized through S7 Communication Services based on ISO-on-TCP (RFC1006). The PLC acts as a server, allowing communication partners to access PLC data without requiring connection configuration during PLC programming.

Activating PUT/GET Access

• To activate S7 Communication Services, enable PUT/GET access in the PLC settings. This allows other applications to access the controller.

Configuring the Connection

The S7 protocol driver differs from other protocol drivers in polling behavior, as it allows only a single polling interval for all mappings. The driver optimizes requests by grouping multiple readings into as few block reads as possible.

For this reason, set the interval in the connection details rather than in individual mappings. If multiple polling rates are required, use separate service commissioning files. Support for different polling rates in a single service commissioning file may be added in the future.

Connection Properties

Hardware-Specific Values

CPU	Rack	Slot
S7-300	0	2
S7-400	See hardware configuration	-
WinAC	See hardware configuration	-
S7-1200	0	1
S7-1500	0	1

Endpoint Properties

Address Structure

The address of a PLC variable is a string with the following structure:

<data block number>,<memory area><data type><byte offset>.<bit position>.<array length>

<data block number>

Name of the data block where the value is stored (e.g., DB10). Only use this parameter if your value is part of a data block.

<memory area>

Memory area where the value is stored.

Do not define this if the target is a data block.

Memory area	Address symbol
input	I
peripheral input	PI
output	Q
peripheral output	PQ
marker	M
counter	C
timer	T

<data type>

Data type of the addressed value. The string data type can only be used in data blocks.

Data type	Address symbol
bit	X (or empty)
byte	B
char	C
word	W
int16	I
dword	DW
int32	DI
real	R
int64	LI (S7-1200/1500 only)
lreal	LR (S7-1200/1500 only)
string	S (only in data blocks)
date_and_time	DT
date_and_time in UTC	DTZ
date_and_time (12 byte)	DTL (S7-1200/1500 only)
date_and_time in UTC (12 byte)	DTLZ (S7-1200/1500 only)

<byte offset>

The byte offset to address.

<bit position>

Specifies the bit position when addressing individual bits. For string data types, this parameter defines the string length.

<array length>

Defines the array length when addressing multiple consecutive values.

The minimum required address information is <data block number> or <memory area>, <data type>, and <byte offset>. Use <bit position> only when addressing individual bits. <array length> is always optional.

Address examples

• MR4 // REAL starting at marker byte 4 (MD4 in STEP 7)

• M32.2 // Bit at marker byte 32 bit 2

• PIW30 // WORD starting at peripheral input byte 30

• PII30 // INT starting at peripheral input byte 30

• DB1,R0.20 // Array of 20 REAL values in DB1 starting at byte 0

• DB1,R4 // Single REAL value

• DB1,REAL8 // Another single REAL value

• DB1,I12.2 // Two INT value array

• DB10,INT6 // DB10.DBW6 as INT

• DB10,I6 // same as above

• DB10,I6.2 // DB10.DBW6 and DB10.DBW8 in an array with length 2

• DB10,S20.30 // String at offset 20 with length of 30 (actual array length 32 due to format of String type, length byte will be read/written)

• DB10,S20.30.3 // Array of 3 strings at offset 20, each with length of 30 (actual array length 32 due to format of String type, length byte will be read/written)

• DB10,C22.30 // Character array at offset 22 with length of 30 (best to not use this with strings as length byte is ignored)

• DB10,X6.0.1 // Bit at DB10.DBX6.0 as array with length 1

• DB10,DT0 // Date and time

• DB10,DTZ0 // Date and time in UTC

To access data from data blocks, disable Optimized Block Access in the data block attributes.

Service Commissioning File Example

2KB

s7-example.yml

Open

s7-example.yml

---
# ----------------------------------------------------------------------------#
# Commissioning File
# ----------------------------------------------------------------------------#
# Copyright: Cybus GmbH (2020)
# Contact: [e-mail]
# ----------------------------------------------------------------------------#
# Source Interface Definition - Siemens S7 PLC
# ----------------------------------------------------------------------------#
# ----------------------------------------------------------------------------#
description: |
  Sample commissioning file for Siemens S7 PLC connectivity and data mapping

metadata:
  name: S7 Protocol Connectivity
  icon: https://www.cybus.io/wp-content/uploads/2019/03/Cybus-logo-Claim-lang.svg
  provider: cybus
  homepage: https://www.cybus.io
  version: 0.0.1

parameters:
  IP_Address:
    type: string
    default: 192.168.10.60

  Port_Number:
    type: integer
    default: 102

  Rack_Number:
    type: integer
    default: 102

  Slot_Number:
    type: integer
    default: 102

  Poll_Interval:
    type: integer
    default: 1000

resources:
  s7Connection:
    type: Cybus::Connection
    properties:
      protocol: S7
      targetState: connected
      connection:
        host: !ref IP_Address
        port: !ref Port_Number
        rack: !ref Rack_Number
        slot: !ref Slot_Number
        pollInterval: !ref Poll_Interval

  s7EndpointQX00:
    type: Cybus::Endpoint
    properties:
      protocol: S7
      connection: !ref s7Connection
      subscribe:
        address: QX0.0

  s7EndpointAIB0:
    type: Cybus::Endpoint
    properties:
      protocol: S7
      connection: !ref s7Connection
      subscribe:
        address: IB0

  mapping:
    type: Cybus::Mapping
    properties:
      mappings:
        - subscribe:
            endpoint: !ref s7EndpointQX00
          publish:
            topic: !sub '${Cybus::MqttRoot}/QX00'
        - subscribe:
            endpoint: !ref s7EndpointAIB0
          publish:
            topic: !sub '${Cybus::MqttRoot}/AIB0'

Output Format on Write

When data is written to an S7 endpoint, the result is published to the /res topic in the following format:

{ 'id': 29194, 'timestamp': 1629351968526, 'result': 0 }

Output Format on Read

When data is read from a Siemens SIMATIC S7, the output is provided as a JSON object with the S7 data in the value property and the reception timestamp in the timestamp property.

{ 'value': '<value>', 'timestamp': '<msSinceEpoch>' }

Input Format on Write

When writing data to a Siemens SIMATIC S7, provide it as a JSON object with the S7 data in the value property:

{ 'value': '<value>' }

Optionally, include an id property in the published message to use as a correlation value for the write operation response.

{ 'value': '<value>', 'id': '<your correlation id>' }

The write operation result is published on the /res topic for the endpoint. For more details on write operations, see Operation Results.