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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

NodeJS version 10 or greater and Node-RED version 1.0 or greater is required.

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`	`M3.2`	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
`DB57,RWORD4`	`DB57.DBW4`	Number	Unsigned 16-bit number at byte 4 of DB 57, interpreted as Little-Endian
`DB13,RDI5` or `DB13,RDINT5`	`DB13.DBD5`	Number	Signed 32-bit number at byte 5 of DB 13, interpreted as Little-Endian
`MRW20`	`MW20`	Number	Unsigned 16-bit number at byte 20 of memory area, interpreted as Little-Endian

*) 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)

Notes on Logo! 8

On the newest Logo! 8.FS4 (and possibly 0BA8) Logic modules there is no need to set the Mode to TSAP any more, instead the default Rack/Slot value of 0/2 works just fine.

The following table shows memory areas accessible without additional settings in the controller program:

Note: These memory areas seem to be read-only from outside the controller, as they are directly used by the function blocks listed in "Logo Block" of the table

Logo Block	Logo VM Range	example Node-RED address	Description
`I`	`1024 - 1031`	`DB1,BYTE1024` or `DB1,X1024.5` or `DB1,WORD1024`	Reads input terminals 1...8 or 6 or 1...16
`AI`	`1032 - 1063`	`DB1,WORD1032`	Reads analog input terminal 1. Always word sized.
`Q`	`1064 - 1071`	`DB1,BYTE1064` or `DB1,X1064.5` or `DB1,WORD1064`	Reads output terminals 1...8 or 6 or 1...16
`AQ`	`1072 - 1103`	`DB1,WORD1072`	Reads analog output terminal 1. Always word sized.
`M`	`1104 - 1117`	`DB1,BYTE1104` or `DB1,X1104.5` or `DB1,WORD1104`	Reads bit flags M1...M8 or M6 or M1...16
`AM`	`1118 - 1245`	`DB1,WORD1118`	Reads analog flag 1. Always word sized.
`NI`	`1246 - 1061`	`DB1,BYTE1246` or `DB1,X1246.5` or `DB1,WORD1246`	Reads network input 1...8 or 6 or 1...16
`NAI`	`1262 - 1389`	`DB1,WORD1262`	Reads analog network input 1. Always word sized.
`NQ`	`1390 - 1405`	`DB1,BYTE1390` or `DB1,X1390.5` or `DB1,WORD1390`	Reads network output 1...8 or 6 or 1...16
`NAQ`	`1406 - 1469`	`DB1,WORD1406`	Reads network output 1. Always word sized.

On the other hand, Logo memory areas VM 0-849 are mutable from outside the controller, but they need to be mapped into the Logo program. Without mapping, data written into these addresses will have no effect on program execution. Used VM addresses in the range mentioned above can be read/written from/into in the Logo program using the "Network" function blocks (in the function block setup use the "Local variable memory (VM)" option to map VMs to the function block).

Some addressing examples:

Logo VM	Example Node-RED address	Description
`0`	`DB1,BYTE0`	R/W access
`1`	`DB1,X1.3`	R/W access Note: use booleans
`2..3`	`DB1,WORD2`	R/W access
`4..7`	`DB1,DWORD4`	R/W access

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

Support

Community support is offered on a best-effort basis via GitHub Issues. For commercial support, please contact us by sending an e-mail to st-one@st-one.io.

License

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