Re: Extract MODBUS Hexadecimal Values - Convert to Decimal - Display on Dashboard

[steve rickus]

In the example data below, you say that the 2 bytes of the 1st register (hex value 'ff fc') = 665.32 decimal. What decoding are you using to get that decimal value? Or, if your actual question is how to decode that hex value into a number, you will have to get that information from the PLC's documentation -- there should be some mention of which encoding is being used in memory to store the data.

Alternately, the node you are using to read the values may have options for how to group and/or interpret the bytes for you. What is the full package name of the node you are using to read the modbus values?

--

Steve

On Monday, March 19, 2018 at 4:51:05 PM UTC-4, Saschin Naidoo wrote:

Hi Guy's and Gals

I would really appreciate assistance with an issue I am having... I basically need to take the MODBUS data I am receiving via TCP, extract characters located at certain positions in msg.payload, these extracted characters will be in Hexadecimal format. I then need to convert these hexadecimal values to decimal values (apply MODBUS scaling factor where required ex. 0.1) and then display on a dashboard gauge.

Below is the data I receive in the debugger via the MODBUS Slave device via a TCP listener:

3: 0xff 

                 - First Register = fffc = 655.32 

4: 0xfc

5: 0x7f

                 - Second Register = 7ffd = 327.65 

6: 0xfd

7: 0x7f

                 - Third Register = 7fff = 327.67

8: 0xff

9: 0xff

                 - Fourth Register = fffc = 655.32 

10: 0xfc

11: 0x0

                 - Fifth Register = 0000 = 0 

12: 0x0

13: 0x1

                 - Sixth Register = 0115 = 27.7 

14: 0x15

15: 0x0

                 - Seventh Register = 0000 = 0 

16: 0x0

[steve rickus]

Saschin, I was asking about the formula you use to convert the hex values into decimal values... but if you are already comfortable doing that, then I'm not sure what question you are asking. And having a picture of the flow is nice, but doesn't really tell me what's going on inside it.

If you still need help, let us know what you've tried -- you can also export your flow as JSON and attach that, so others can try it out...

--

Steve

On Tuesday, March 20, 2018 at 3:48:00 AM UTC-4, Saschin Naidoo wrote:

As a next step, I need to take the MODBUS responses from the TCP listener and pass the payload (in the second object, from [0 ... 9] AND [10 ...18]) into a function to extract the Hex values and apply the conversion to decimal, then pass on this decimal value as a function output to a dashboard ui node.

[Colin Law]

Are you sure strHexCodes is a string?  Feed it to a debug node and check what type it says it is.

You could insert at the top of the function

node.warn("Typeof strHexCodes is: " + typeof strHexCodes);

and it will display that in the debug window

Also you might find substring a useful function.
https://www.w3schools.com/jsref/jsref_substring.asp

On 26 March 2018 at 09:15, Saschin Naidoo <sas...@trillcom.co.za> wrote:

Hi Steve

Sorry for the late response.

Please see below the function I have written in JavaScript but Node-Red throws the error: "TypeError: strHexCodes.charAt is not a function"

var strHexCodes = msg.payload;

var reg0 = strHexCodes.charAt(0).concat(strHexCodes.charAt(1)); 

var reg1 = strHexCodes.charAt(2).concat(strHexCodes.charAt(3)); 

var reg2 = strHexCodes.charAt(4).concat(strHexCodes.charAt(5)); 

var reg3 = strHexCodes.charAt(6).concat(strHexCodes.charAt(7)).concat(strHexCodes.charAt(8)).concat(strHexCodes.charAt(9));

var reg4 = strHexCodes.charAt(10).concat(strHexCodes.charAt(11)).concat(strHexCodes.charAt(12)).concat(strHexCodes.charAt(13));

var reg5 = strHexCodes.charAt(14).concat(strHexCodes.charAt(15)).concat(strHexCodes.charAt(16)).concat(strHexCodes.charAt(17));

var reg6 = strHexCodes.charAt(18).concat(strHexCodes.charAt(19)).concat(strHexCodes.charAt(20)).concat(strHexCodes.charAt(21));

var reg7 = strHexCodes.charAt(22).concat(strHexCodes.charAt(23)).concat(strHexCodes.charAt(24)).concat(strHexCodes.charAt(25));

var reg8 = strHexCodes.charAt(26).concat(strHexCodes.charAt(27)).concat(strHexCodes.charAt(28)).concat(strHexCodes.charAt(29));

var reg9 = strHexCodes.charAt(30).concat(strHexCodes.charAt(31)).concat(strHexCodes.charAt(32)).concat(strHexCodes.charAt(33));

var reg10 = strHexCodes.charAt(34).concat(strHexCodes.charAt(35)).concat(strHexCodes.charAt(36)).concat(strHexCodes.charAt(37));

return [(parseInt(reg3, 16) / 100).toFixed(2), (parseInt(reg4, 16) / 100).toFixed(2), (parseInt(reg5, 16) / 100).toFixed(2), (parseInt(reg6, 16) / 100).toFixed(2), (parseInt(reg7, 16) / 100).toFixed(2), (parseInt(reg8, 16) / 10).toFixed(1), (parseInt(reg9, 16) / 100).toFixed(2), (parseInt(reg10, 16) / 100).toFixed(2)];

Flow:

[{"id":"37536f03.bb2ce","type":"mongodb out","z":"76c6836d.e441cc","mongodb":"7d092f74.c00cb","name":"","collection":"cp_values","payonly":false,"upsert":false,"multi":false,"operation":"store","x":605.2857055664062,"y":520.4285278320312,"wires":[]},{"id":"27b7dbaa.59c5a4","type":"ui_gauge","z":"76c6836d.e441cc","name":"Oil Pressure","group":"d4357969.3701f","order":1,"width":"","height":"","gtype":"gage","title":"Oil Pressure","label":"Bar","format":"{{value}}","min":0,"max":"10","colors":["#00b500","#e6e600","#ca3838"],"seg1":"3","seg2":"6","x":1433,"y":103,"wires":[]},{"id":"28fb3864.3854b8","type":"function","z":"76c6836d.e441cc","name":"Generator Oil Pressure","func":"words = msg.payload.replace(/\\n/g, \",\");\nvar res = words.split(\",\");\n\nvar value = parseFloat(res[18]);\n//value = value*8.163;\n\nmsg.payload = (Math.round((value) * 100) / 100);\nreturn msg;","outputs":1,"noerr":0,"x":863,"y":103,"wires":[["27b7dbaa.59c5a4"]]},{"id":"5f8c3b52.f10784","type":"template","z":"76c6836d.e441cc","name":"TCP Payload","field":"payload","fieldType":"msg","format":"handlebars","syntax":"mustache","template":"This is the payload: {{payload}} !","output":"str","x":434.42860412597656,"y":198.7142791748047,"wires":[["28fb3864.3854b8","213e691c.2589d6","eff08d54.1c65d","c734c648.c1fd48","14d9de99.3bf781","5a12c0f3.efefb","d8051fb9.f7c3"]]},{"id":"b4409848.c1a558","type":"ui_gauge","z":"76c6836d.e441cc","name":"Fuel Level","group":"d4357969.3701f","order":2,"width":"","height":"","gtype":"gage","title":"Fuel Level","label":"Litres/Diesel","format":"{{value}}","min":"0","max":"450","colors":["#ff2600","#e6e600","#00f900"],"seg1":"150","seg2":"300","x":1423,"y":163,"wires":[]},{"id":"90aacc50.44bb","type":"ui_gauge","z":"76c6836d.e441cc","name":"Engine Temperature","group":"caf75ba2.a708a8","order":2,"width":"","height":"","gtype":"gage","title":"Engine Temperature","label":"Deg. Celcius","format":"{{value}}","min":0,"max":"110","colors":["#00b500","#e6e600","#ca3838"],"seg1":"30","seg2":"90","x":1461.5714721679688,"y":222.99999809265137,"wires":[]},{"id":"46ae16b7.808928","type":"ui_gauge","z":"76c6836d.e441cc","name":"Battery Voltage","group":"caf75ba2.a708a8","order":1,"width":"","height":"","gtype":"gage","title":"Battery Voltage","label":"Volts","format":"{{value}}","min":0,"max":"15","colors":["#ff2600","#e6e600","#00f900"],"seg1":"5","seg2":"10","x":1443,"y":283,"wires":[]},{"id":"213e691c.2589d6","type":"function","z":"76c6836d.e441cc","name":"Generator Fuel Level","func":"words = msg.payload.replace(/\\n/g, \",\");\nvar res = words.split(\",\");\n\nvar value = parseFloat(res[19]);\nvalue = value+420;\n\nmsg.payload = (Math.round((value) * 100) / 100);\nreturn msg;","outputs":1,"noerr":0,"x":863,"y":163,"wires":[["b4409848.c1a558"]]},{"id":"eff08d54.1c65d","type":"function","z":"76c6836d.e441cc","name":"Generator Engine Temperature","func":"words = msg.payload.replace(/\\n/g, \",\");\nvar res = words.split(\",\");\n\nvar value = parseFloat(res[17]);\nvalue = value*9.3;\n\nmsg.payload = (Math.round((value) * 100) / 100);\nreturn msg;","outputs":1,"noerr":0,"x":893,"y":223,"wires":[["90aacc50.44bb"]]},{"id":"c734c648.c1fd48","type":"function","z":"76c6836d.e441cc","name":"Generator Battery Voltage","func":"words = msg.payload.replace(/\\n/g, \",\");\nvar res = words.split(\",\");\n\nvar value = parseFloat(res[21]);\n//value = value*8.163;\n\nmsg.payload = (Math.round((value) * 100) / 100);\nreturn msg;","outputs":1,"noerr":0,"x":873,"y":283,"wires":[["46ae16b7.808928"]]},{"id":"4847affb.88777","type":"tcp in","z":"76c6836d.e441cc","name":"","server":"server","host":"localhost","port":"51234","datamode":"stream","datatype":"buffer","newline":"","topic":"","base64":false,"x":122.32142639160156,"y":197.07142448425293,"wires":[["ffa657cc.b96098","5f8c3b52.f10784","95f12997.0c6948"]]},{"id":"7b43d1a9.13351","type":"ui_gauge","z":"76c6836d.e441cc","name":"Oil Temperature","group":"d4357969.3701f","order":0,"width":0,"height":0,"gtype":"gage","title":"Oil Temperature","label":"Deg. Celcius","format":"{{value}}","min":0,"max":"200","colors":["#00b500","#e6e600","#ca3838"],"seg1":"75","seg2":"150","x":1443.0713500976562,"y":335.5714454650879,"wires":[]},{"id":"66b76332.0a85fc","type":"ui_gauge","z":"76c6836d.e441cc","name":"Charge Alternator Voltage","group":"caf75ba2.a708a8","order":0,"width":0,"height":0,"gtype":"gage","title":"Charge Alternator Voltage","label":"Volts","format":"{{value}}","min":0,"max":"40","colors":["#00b500","#e6e600","#ca3838"],"seg1":"10","seg2":"30","x":1472.1427841186523,"y":389.99998474121094,"wires":[]},{"id":"8f99c951.3e7d08","type":"ui_gauge","z":"76c6836d.e441cc","name":"Engine Speed","group":"d4357969.3701f","order":0,"width":0,"height":0,"gtype":"gage","title":"Engine Speed","label":"units","format":"{{value}}","min":0,"max":"6000","colors":["#00b500","#e6e600","#ca3838"],"seg1":"2000","seg2":"4000","x":1446.4284057617188,"y":451.4286165237427,"wires":[]},{"id":"14d9de99.3bf781","type":"function","z":"76c6836d.e441cc","name":"Generator Oil Temperature","func":"\nreturn msg;","outputs":1,"noerr":0,"x":887.8571395874023,"y":335.71428394317627,"wires":[["7b43d1a9.13351"]]},{"id":"5a12c0f3.efefb","type":"function","z":"76c6836d.e441cc","name":"Generator Alternator Voltage","func":"\nreturn msg;","outputs":1,"noerr":0,"x":887.8571357727051,"y":390.0000190734863,"wires":[["66b76332.0a85fc"]]},{"id":"d8051fb9.f7c3","type":"function","z":"76c6836d.e441cc","name":"Generator Engine Speed","func":"\nreturn msg;","outputs":1,"noerr":0,"x":877.8571548461914,"y":451.4285945892334,"wires":[["8f99c951.3e7d08"]]},{"id":"ffa657cc.b96098","type":"debug","z":"76c6836d.e441cc","name":"","active":true,"console":"false","complete":"true","x":414.49998474121094,"y":304.14284324645996,"wires":[]},{"id":"91efcea.6a40c3","type":"inject","z":"76c6836d.e441cc","name":"","topic":"","payload":"0,0,0,0,0,0,0,0,0,0,0,0,0,0","payloadType":"str","repeat":"","crontab":"","once":false,"x":156.78571701049805,"y":62.714287757873535,"wires":[["5f8c3b52.f10784"]]},{"id":"95f12997.0c6948","type":"function","z":"76c6836d.e441cc","name":"Generate Decimal Values","func":"var strHexCodes = msg.payload;\nvar reg0 = strHexCodes.charAt(0).concat(strHexCodes.charAt(1)); \nvar reg1 = strHexCodes.charAt(2).concat(strHexCodes.charAt(3)); \nvar reg2 = strHexCodes.charAt(4).concat(strHexCodes.charAt(5)); \nvar reg3 = strHexCodes.charAt(6).concat(strHexCodes.charAt(7)).concat(strHexCodes.charAt(8)).concat(strHexCodes.charAt(9));\nvar reg4 = strHexCodes.charAt(10).concat(strHexCodes.charAt(11)).concat(strHexCodes.charAt(12)).concat(strHexCodes.charAt(13));\nvar reg5 = strHexCodes.charAt(14).concat(strHexCodes.charAt(15)).concat(strHexCodes.charAt(16)).concat(strHexCodes.charAt(17));\nvar reg6 = strHexCodes.charAt(18).concat(strHexCodes.charAt(19)).concat(strHexCodes.charAt(20)).concat(strHexCodes.charAt(21));\nvar reg7 = strHexCodes.charAt(22).concat(strHexCodes.charAt(23)).concat(strHexCodes.charAt(24)).concat(strHexCodes.charAt(25));\nvar reg8 = strHexCodes.charAt(26).concat(strHexCodes.charAt(27)).concat(strHexCodes.charAt(28)).concat(strHexCodes.charAt(29));\nvar reg9 = strHexCodes.charAt(30).concat(strHexCodes.charAt(31)).concat(strHexCodes.charAt(32)).concat(strHexCodes.charAt(33));\nvar reg10 = strHexCodes.charAt(34).concat(strHexCodes.charAt(35)).concat(strHexCodes.charAt(36)).concat(strHexCodes.charAt(37));\n\nreturn [(parseInt(reg3, 16) / 100).toFixed(2), (parseInt(reg4, 16) / 100).toFixed(2), (parseInt(reg5, 16) / 100).toFixed(2), (parseInt(reg6, 16) / 100).toFixed(2), (parseInt(reg7, 16) / 100).toFixed(2), (parseInt(reg8, 16) / 10).toFixed(1), (parseInt(reg9, 16) / 100).toFixed(2), (parseInt(reg10, 16) / 100).toFixed(2)];","outputs":"8","noerr":0,"x":327,"y":419,"wires":[["402ff972.c6d6e8"],[],[],[],[],[],[],[]]},{"id":"402ff972.c6d6e8","type":"debug","z":"76c6836d.e441cc","name":"Oil Pressure","active":true,"console":"false","complete":"true","x":552,"y":387,"wires":[]},{"id":"7d092f74.c00cb","type":"mongodb","z":"76c6836d.e441cc","hostname":"94.130.224.94","port":"27017","db":"local","name":""},{"id":"d4357969.3701f","type":"ui_group","z":"","name":"Critical Operating Parameters","tab":"46d3d70f.a39358","order":2,"disp":true,"width":"5"},{"id":"caf75ba2.a708a8","type":"ui_group","z":"","name":"Critical Operating Parameters 2","tab":"46d3d70f.a39358","order":4,"disp":true,"width":"6"},{"id":"46d3d70f.a39358","type":"ui_tab","z":"","name":"PDS Genset Monitoring Dashboard","icon":"dashboard","order":2}]

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