node-red-contrib-s7

node-red-contrib-s7

A Node-RED node to interact with Siemens S7 PLCs.

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

Install

You can install this node directly from the "Manage Palette" menu in the Node-RED interface.

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
DB1,DT0	-	Date**	A timestamp in the DATE_AND_TIME format
DB1,DTZ10	-	Date**	A timestamp in the DATE_AND_TIME format, in UTC
DB2,DTL2	-	Date**	A timestamp in the DTL format
DB2,DTLZ12	-	Date**	A timestamp in the DTL format, in UTC

• *) Note that strings on the PLC uses 2 extra bytes at start for size/length of the string
• **) Note that javascript's Date are always represented in UTC. Please use other nodes like node-red-contrib-moment to properly handle type conversions

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)

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) 2016-2020, ST-One Ltda., Guilherme Francescon Cittolin [e-mail]

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