plcindustry 2.1.1

A Node-RED node to interact with Siemens S7 PLCs

npm install plcindustry

A Node-RED node to interact with Siemens S7 PLCs. Based on the awesome work of plcpeople/nodes7.

This node was created by Smart-Tech as part of the ST-One project.

Install

You can install this node directly from the "Manage Palette" menu in the Node-RED interface. An optional compilation step is only necessary for supporting MPI-USB adapter.

Alternatively, run the following command in your Node-RED user directory - typically ~/.node-red on Linux or %HOMEPATH%\.nodered on Windows

    npm install node-red-contrib-s7

Usage

Each connection to a PLC is represented by the S7 Endpoint configuration node. You can configure the PLC's Address, the variables available and their addresses, and the cycle time for reading the variables.

The S7 In node makes the variable's values available in a flow in three different modes:

  • Single variable: A single variable can be selected from the configured variables, and a message is sent every cycle, or only when it changes if diff is checked. msg.payload contains the variable's value and msg.topic has the variable's name.
  • All variables, one per message: Like the Single variable mode, but for all variables configured. If diff is checked, a message is sent everytime any variable changes. If diff is unchecked, one message is sent for every variable, in every cycle. Care must be taken about the number of messages per second in this mode.
  • All variables: In this mode, msg.payload contains an object with all configured variables and their values. If diff is checked, a message is sent if at least one of the variables changes its value.

Variable addressing

The variables and their addresses configured on the S7 Endpoint follow a slightly different scheme than used on Step 7 or TIA Portal. Here are some examples that may guide you on addressing your variables:

Address Step7 equivalent JS Data type Description
DB5,X0.1 DB5.DBX0.1 Boolean Bit 1 of byte 0 of DB 5
DB23,B1 or DB23,BYTE1 DB23.DBB1 Number Byte 1 (0-255) of DB 23
DB100,C2 or DB100,CHAR2 DB100.DBB2 String Byte 2 of DB 100 as a Char
DB42,I3 or DB42,INT3 DB42.DBW3 Number Signed 16-bit number at byte 3 of DB 42
DB57,WORD4 DB57.DBW4 Number Unsigned 16-bit number at byte 4 of DB 57
DB13,DI5 or DB13,DINT5 DB13.DBD5 Number Signed 32-bit number at byte 5 of DB 13
DB19,DW6 or DB19,DWORD6 DB19.DBD6 Number Unsigned 32-bit number at byte 6 of DB 19
DB21,R7 or DB21,REAL7 DB21.DBD7 Number Floating point 32-bit number at byte 7 of DB 21
DB2,S7.10* - String String of length 10 starting at byte 7 of DB 2
I1.0 or E1.0 I1.0 or E1.0 Boolean Bit 0 of byte 1 of input area
Q2.1 or A2.1 Q2.1 or A2.1 Boolean Bit 1 of byte 2 of output area
M3.2 QM3.2 Boolean Bit 2 of byte 3 of memory area
IB4 or EB4 IB4 or EB4 Number Byte 4 (0 -255) of input area
QB5 or AB5 QB5 or AB5 Number Byte 5 (0 -255) of output area
MB6 MB6 Number Byte 6 (0 -255) of memory area
IC7 or EC7 IB7 or EB7 String Byte 7 of input area as a Char
QC8 or AC8 QB8 or AB8 String Byte 8 of output area as a Char
MC9 MB9 String Byte 9 of memory area as a Char
II10 or EI10 IW10 or EW10 Number Signed 16-bit number at byte 10 of input area
QI12 or AI12 QW12 or AW12 Number Signed 16-bit number at byte 12 of output area
MI14 MW14 Number Signed 16-bit number at byte 14 of memory area
IW16 or EW16 IW16 or EW16 Number Unsigned 16-bit number at byte 16 of input area
QW18 or AW18 QW18 or AW18 Number Unsigned 16-bit number at byte 18 of output area
MW20 MW20 Number Unsigned 16-bit number at byte 20 of memory area
IDI22 or EDI22 ID22 or ED22 Number Signed 32-bit number at byte 22 of input area
QDI24 or ADI24 QD24 or AD24 Number Signed 32-bit number at byte 24 of output area
MDI26 MD26 Number Signed 32-bit number at byte 26 of memory area
ID28 or ED28 ID28 or ED28 Number Unsigned 32-bit number at byte 28 of input area
QD30 or AD30 QD30 or AD30 Number Unsigned 32-bit number at byte 30 of output area
MD32 MD32 Number Unsigned 32-bit number at byte 32 of memory area
IR34 or ER34 IR34 or ER34 Number Floating point 32-bit number at byte 34 of input area
QR36 or AR36 QR36 or AR36 Number Floating point 32-bit number at byte 36 of output area
MR38 MR38 Number Floating point 32-bit number at byte 38 of memory area

*) Note that strings on the PLC uses 2 extra bytes at start for size/length of the string

Notes on S7-1200/1500

These newer PLCs offer an "extended" version of the S7 Protocol, while we have only a "basic" version of it.

Therefore, some additional configuration steps on the PLC are necessary:

  • "Optimized block access" must be disabled for the DBs we want to access (image)
  • In the "Protection" section of the CPU Properties, enable the "Permit access with PUT/GET" checkbox (image)

Wishlist

  • Perform data type validation on the variables list, preventing errors on the runtime

Bugs and enhancements

Please share your ideas and experiences on the Node-RED forum, or open an issue on the page of the project on GitHub

License

Copyright: (c) 2016-2019, Smart-Tech, Guilherme Francescon Cittolin guilherme.francescon@netsmarttech.com

GNU General Public License v3.0+ (see LICENSE or https://www.gnu.org/licenses/gpl-3.0.txt)

Node Info

Version: 2.1.1
Updated 4 years, 7 months ago
License: GPL-3.0-or-later
Rating: 0.0
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Nodes

  • s7 endpoint
  • s7 in
  • s7 out
  • s7 control

Keywords

  • hardware
  • s7
  • siemens
  • plc
  • node-red

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