Using push into a for loop

Industrial
1

Hi there,

I'm trying to push values from modbus into an array. The values are encoded i floating format. I managed to convert bytes (4) into single floating :sweat_smile:
The "function" node returns all this values into an array if I push them one by one:

[{"id":"b2559ff0.bd2228","type":"modbus-read","z":"4f90fdb9.b07554","name":"","topic":"","showStatusActivities":true,"logIOActivities":false,"showErrors":false,"unitid":"","dataType":"HoldingRegister","adr":"121","quantity":"6","rate":"5","rateUnit":"s","delayOnStart":false,"startDelayTime":"","server":"badbc08.08534c","useIOFile":false,"ioFile":"","useIOForPayload":false,"x":190,"y":180,"wires":[[],["ab597b10.1d0db8"]]},{"id":"ab597b10.1d0db8","type":"function","z":"4f90fdb9.b07554","name":"","func":"const buf = Buffer.from(msg.payload.buffer);\nbuf.swap16();\n\nvar my_list, i;\nconst len = (msg.payload.buffer.length);\nmy_list = [];\n\n// push values 1 by 1 in array\nmy_list.push(buf.readFloatLE(0));\nmy_list.push(buf.readFloatLE(4));\nmy_list.push(buf.readFloatLE(8));\n\n// push values in for loop\n//for (i=0; i<=len; i=+ 4){\n//    my_list.push(buf.readFloatLE(i));\n//}\n\nmsg.payload = my_list;\nreturn msg;","outputs":1,"noerr":0,"x":310,"y":80,"wires":[["fdbbcc26.59d768"]]},{"id":"fdbbcc26.59d768","type":"debug","z":"4f90fdb9.b07554","name":"","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","x":710,"y":80,"wires":[]},{"id":"badbc08.08534c","type":"modbus-client","z":"","name":"KACO","clienttype":"tcp","bufferCommands":true,"stateLogEnabled":false,"tcpHost":"192.168.200.111","tcpPort":"502","tcpType":"DEFAULT","serialPort":"/dev/ttyUSB","serialType":"RTU-BUFFERD","serialBaudrate":"9600","serialDatabits":"8","serialStopbits":"1","serialParity":"none","serialConnectionDelay":"100","unit_id":"1","commandDelay":"1","clientTimeout":"1000","reconnectTimeout":"2000"}]
]

It wouldn't be a problem if there were just few values. But I have plenty of registers. To make my code more efficient, I need to push all this values into an array inside a for loop (ref. the commented lines in the code above), but when I run this part of code, Node-Red crashes every time.
Some help would be appreciated :slight_smile:

Regards,

Yoba

2

Maybe its the
i<=len
that should be
i<len
?

3

Have a look at node-red-contrib-buffer-parser. Whilst it may not do exactly what you are asking for (or may, I am not sure) it may be that it would be useful for you.

4

wrong syntax

for (i=0; i<=len; i=+ 4){

correct syntax

for (i=0; i<=len; i += 4){
5

Thank you @hotNipi for your quick answer :slight_smile:

6

@yoba as @Colin suggested, buffer parser takes all the pain out of making sense of your data.

e.g...

image
image962×1175 110 KB

Demo flow...

[{"id":"ab597b10.1d0db8","type":"function","z":"5bd4aa78.31d114","name":"","func":"const buf = Buffer.from(msg.payload.buffer);\nbuf.swap16();\n\nvar my_list, i;\nconst len = (msg.payload.buffer.length);\nmy_list = [];\n\n// push values 1 by 1 in array\nmy_list.push(buf.readFloatLE(0));\nmy_list.push(buf.readFloatLE(4));\nmy_list.push(buf.readFloatLE(8));\n\n// // push values in for loop\n// for (i=0; i<len; i=+ 4){\n//     my_list.push(buf.readFloatLE(i));\n// }\n\nmsg.payload = my_list;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":924,"y":96,"wires":[["fdbbcc26.59d768"]]},{"id":"fdbbcc26.59d768","type":"debug","z":"5bd4aa78.31d114","name":"Function","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":1100,"y":96,"wires":[]},{"id":"cb3e7a56.719758","type":"inject","z":"5bd4aa78.31d114","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":623,"y":192,"wires":[["ed6c26a7.0bfb08"]],"l":false},{"id":"ed6c26a7.0bfb08","type":"function","z":"5bd4aa78.31d114","name":"Fake Modbus","func":"msg.payload = {\n    buffer : Buffer.from([0,1,0,2,0,3,0,4,0,5,0,6,0,7,0,8])\n}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":720,"y":192,"wires":[["25617943.c50d26"]]},{"id":"25617943.c50d26","type":"buffer-parser","z":"5bd4aa78.31d114","name":"","data":"payload.buffer","dataType":"msg","specification":"spec","specificationType":"ui","items":[{"type":"floatle","name":"item1","offset":0,"length":1,"offsetbit":0,"scale":"1","mask":""},{"type":"floatle","name":"item2","offset":4,"length":1,"offsetbit":0,"scale":"1","mask":""},{"type":"floatle","name":"item3","offset":8,"length":1,"offsetbit":0,"scale":"1","mask":""}],"swap1":"swap16","swap2":"","swap3":"","swap1Type":"swap","swap2Type":"swap","swap3Type":"swap","msgProperty":"payload","msgPropertyType":"str","resultType":"value","resultTypeType":"output","multipleResult":false,"fanOutMultipleResult":false,"setTopic":true,"outputs":1,"x":934,"y":192,"wires":[["b1fec79a.da4a78"]]},{"id":"b1fec79a.da4a78","type":"debug","z":"5bd4aa78.31d114","name":"Parser","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":1090,"y":192,"wires":[]},{"id":"c2aee09b.5ac13","type":"inject","z":"5bd4aa78.31d114","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":623,"y":96,"wires":[["567c6031.02666"]],"l":false},{"id":"567c6031.02666","type":"function","z":"5bd4aa78.31d114","name":"Fake Modbus","func":"msg.payload = {\n    buffer : Buffer.from([0,1,0,2,0,3,0,4,0,5,0,6,0,7,0,8])\n}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":720,"y":96,"wires":[["ab597b10.1d0db8"]]},{"id":"97782186.7c8bf","type":"inject","z":"5bd4aa78.31d114","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":623,"y":464,"wires":[["c8767342.8d7d3"]],"l":false},{"id":"c8767342.8d7d3","type":"function","z":"5bd4aa78.31d114","name":"Fake Modbus 3 floats","func":"msg.payload = {\n    buffer : Buffer.from([0,1,0,2,0,3,0,4,0,5,0,6])\n}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":740,"y":464,"wires":[["102a549f.38297b"]]},{"id":"102a549f.38297b","type":"buffer-parser","z":"5bd4aa78.31d114","name":"","data":"payload.buffer","dataType":"msg","specification":"spec","specificationType":"ui","items":[{"type":"floatle","name":"item1","offset":0,"length":-1,"offsetbit":0,"scale":"1","mask":""}],"swap1":"swap16","swap2":"","swap3":"","swap1Type":"swap","swap2Type":"swap","swap3Type":"swap","msgProperty":"payload","msgPropertyType":"str","resultType":"value","resultTypeType":"output","multipleResult":false,"fanOutMultipleResult":false,"setTopic":true,"outputs":1,"x":934,"y":464,"wires":[["b365ecd6.bfe85"]]},{"id":"b365ecd6.bfe85","type":"debug","z":"5bd4aa78.31d114","name":"","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":1110,"y":464,"wires":[]},{"id":"ed450c73.8a799","type":"inject","z":"5bd4aa78.31d114","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":623,"y":512,"wires":[["d0aa6936.981118"]],"l":false},{"id":"d0aa6936.981118","type":"function","z":"5bd4aa78.31d114","name":"Fake Modbus 5 floats","func":"msg.payload = {\n    buffer : Buffer.from([0,1,0,2,0,3,0,4,0,5,0,6,0,7,0,8,0,9,0,10])\n}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":740,"y":512,"wires":[["102a549f.38297b"]]},{"id":"11dd3da7.31a7f2","type":"comment","z":"5bd4aa78.31d114","name":"Dynamic length","info":"","x":656,"y":432,"wires":[]},{"id":"73e2049d.d0ac6c","type":"inject","z":"5bd4aa78.31d114","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":623,"y":304,"wires":[["f7146e75.96401"]],"l":false},{"id":"f7146e75.96401","type":"function","z":"5bd4aa78.31d114","name":"Fake Modbus","func":"msg.payload = {\n    buffer : Buffer.from([0,1,0,2,0,3,0,4,0,5,0,6,0,7,0,8])\n}\nreturn 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7

Hi @Steve-Mcl ,

I took a look at the buffer parser as @Colin suggested. It's exactly what I need. The only problem is I use IoT2040 from Siemens, and I tried to install it without any success. I wonder if the problem is coming from the Debian used. It's a Yocto Rocko.
Do you have any other suggestion of OS to use on IoT2040?

I really appreciate all the good and quick answers. This forum rocks !!!

8

Ah, that old chestnut. An overpriced out of date piece of hardware!

The reason is likely the node version on that unit is obsolete.

The solution is: replace it with a £35 raspberry pi :wink:

9

Mind you, that said, i am certain it still installs - just dont try to use BigInt64

What error do you get?

EDIT:
Are you using custom firmware on the IoT2040 ?

What node version is installed?

from a terminal, enter node -v

Also, what node-red version are you on?

10

Hi again,

Sorry for the late answer. I was busy trying to install new image (v2.6.1) from Siemens. Cause I was not sure which version was running on SD card. I used this time npm commands from the terminal and installed buffer parser inside folder .node-red
To answer your question, the versions are:
root@iot2000:~# node -v
v8.16.0
root@iot2000:~# npm -v
6.4.1

Are they the latest versions?

11

No where near. Node 8's End of Life is December 31, 2019

https://nodejs.org/en/about/releases/

But I think buffer-parser will install on V8

Try and if it fails, show me the error(s)

PS: dont forget to tell me NODE-RED version. (its on the node-red menu)

12

Node-RED version (from menu): v0.20.7

13

wow - yeah - that wont work either.

I do believe you can update node-red to very latest V1.2.9 (even on node v8)

npm install -g --unsafe-perm node-red

14

Hello!

I struggled to upgrade this IoT2000, but I managed to get this result:
18 Mar 15:24:28 - [info] Node-RED version: v1.2.9
18 Mar 15:24:28 - [info] Node.js version: v8.16.0
18 Mar 15:24:28 - [info] Linux 4.4.185-cip35 ia32 LE

So now I have buffer parser into Node Red as you recommended, but I get error:
Error: data is not an array or a buffer

[{"id":"67a1ac1.d025d54","type":"buffer-parser","z":"ea67c445.9798f8","name":"","data":"payload","dataType":"msg","specification":"spec","specificationType":"ui","items":[{"type":"floatle","name":"item1","offset":0,"length":4,"offsetbit":0,"scale":"1","mask":""}],"swap1":"swap16","swap2":"","swap3":"","swap1Type":"swap","swap2Type":"swap","swap3Type":"swap","msgProperty":"payload","msgPropertyType":"str","resultType":"object","resultTypeType":"output","multipleResult":false,"fanOutMultipleResult":false,"setTopic":true,"outputs":1,"x":430,"y":280,"wires":[["fbd9cc4a.104be"]]}]

I've tried different properties, but it didn't help. Could you please tell me how to convert msg.payload (array of integers) into individual topic/payload messages. It's for sending MQTT :slight_smile:

15

image

Also, check out the actual working demo i posted...

16

Hi @Steve-Mcl ,

Thank you for your quick answer. I appreciate a lot.
I didn't know that the property (as you circled) could be changed. I set it to msg.payload.buffer
Now everthing seems to work properly :ok_hand:

Bonus question: could it be possible to put your sample code into the node contrib?
https://flows.nodered.org/node/node-red-contrib-buffer-parser
This one was way better than the two presented

Have a nice week-end

17

I will consider it :stuck_out_tongue:

18

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