Siemens SIMATIC S7

The Simatic S7 is a product line of PLCs (S7-200, S7-300, S7-400, S7-1200, S7-1500) by Siemens that are widely used in industrial automation. The S7 is capable of connecting several sensors and actuators through digital or analog IOs which can be modular extended.

The S7 PLC can be projected and programmed with STEP7 (TIA Portal) software from Siemens.

The read and write access to data on the PLC can be realized through the S7 Communication Services based on ISO-on-TCP (RFC1006). In this case the PLC acts as a server allowing communication partners to access PLC data without the need of projecting the incoming connections during PLC programming.

To activate the S7 Communication Services you need to enable PUT/GET access in PLC Settings! You should keep in mind that this opens up the controller access by other applications as well.

Configuring the connection

The S7 protocol driver behaves differently from other protocol drivers when polling, because it only allows a single polling interval to be set for all mappings. The reason for this is that the driver optimizes the request as it groups multiple readings into as few block reads as possible. For this reason the interval is set in the connection details, and not in the mappings for this protocol. If multiple different polling rates are required, you should consider using multiple commissioning files. Support for different polling rates in a single 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

The address of a PLC variable is a string built like this:

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

<data block number>

Name of the data block the value is stored in 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. Must not be defined if 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. Data type “string” 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 offset of the byte to address.

<bit position>

To address a bit position place it here. In case you are addressing a string data type this parameter is the string length.

<array length>

To address multiple values in a row define the length of the array here.

The minimum information any address must contain is <data block number> or <memory area>, <data type> and <byte offset>. <bit position> is only necessary for addressing 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 you need to disable “Optimized Block Access” in data block attributes!

Service Commissioning File Example

2KB

s7-example.yml

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 a S7 endpoint, you will get the result of the operation over the /res topic like this:

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

Output Format on Read

If data is read from Siemens SIMATIC S7 the output will be provided as JSON object, with the actual S7 data in the property value, and the reception timestamp in the property timestamp.

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

Input Format on Write

If data is written to Siemens SIMATIC S7 it must be provided as JSON object, with the actual S7 data in the property value:

{ 'value': '<value>' }

Additionally an id property can be provided in the published message to use as a correlation value for the response of the write operation.

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

The result of a write operation is published on the /res topic for the Endpoint see Operation results for more details on writing operations