I've been watching a lot of your tutorials lately. Unfortunately, I have a lot of doubts if what I need to do is "doable" with MQTT + Node red.
I'll try to explain in a simple way: I'm using a Software from Pozyx to get some coordinates from a RFID device. This software sends a payload via MQTT with some info (coordinates, timestamp, acceleration and blablabla). What I need to do is: receive this info, filter the payload to get only the coordinates, apply these coordinates in some matrix calculus (pure math) and show the result of the matrix in a dashboard.
What I was able to do: establish a broker to transfer the data via MQTT, connect my MQTT to my node-red "ambient", receive this payload and filter it to get only the coordinates.
Finally, my doubt is: is it possible to make the calculus on the node-red ambient or I need to run a nodejs server, send the info from my mqtt to the nodejs, do the calculation and then send it to node-red dashboard?
What I want to get is the "X" and the "tagId" of this "X". For example, I want to show in my dashboard this:
tagId = 26398; X = 4834
tagId = 26459; X = 348
tagId = 26398; X = 4785
I could split my coordinates and get only the "X" value, but I can't keep the "X value" and the "tagId" at the same time using the split (function string). Can you help me?
That payload is a string if you pass it through a JSON node it should convert it to a javascript object which you can manipulate with Node-RED
If you then send it to a debug node the page in the docs called “working with messages” will show you some neat tips of how to get the path to any piece of data you want
Thank you for the "working with messages", it really helped. I was able to split my payload, exactly the way I want. My only problem is: I want to split the "object", I mean, I receive the payload from two different sensors, each one with one tagId and one X coordinates. I want to keep the pair together and compare these two... I don't know how to "split" the X from the rest and maintain the relation with the tagId.
not quite clear what you want but you could use a change node to move the parts around a bit if you like... eg move msg.payload.tagId to msg.tagId and also move msg.payload.coordinates.x to msg.payload - then you would just have the two parts on the msg (as the x would have now replaced the rest of the payload).
Guys, I'm really sorry if I didn't make it quite clear. Let's try again:
This is what I want to show in my dashboard
The main idea is: I'll put a sensor in a position and I'll have this position. For example, my sensor 01 (tagId 24555) will be at X = 30. The another sensor (02 - tagId 23859) I'll install at X = 60. What I need to do with my dashboard is: read the tagId (in order to know about which sensor I'm getting the X) and compare with my default value.
I mean: Sensor 01 (tagId 24555) was installed at X = 30. If my dashboard shows that my tagId 24555 is with X 45, I'll know that something wrong happened.
I hope that you guys can understand now, thank you a lot for all the effort
The easiest way to get that going is probably to use dashboard Text nodes for the two columns. You can use a Switch node to send the messages down different paths to the individual text nodes. In the switch node you can test for msg.payload.tagId == string 26459 and send that message to output 1, if it is 26398 send it to output 2, and so on.
