Get string from serial port and convert to separate key

General
1

I am getting "Humidity: 64.40%, Temperature: 32.00 Celsius" which is in string from my serial port. I wish to change it to key value data. This is so that I can do gauge for humidity and temperature separately. Do advice. Do I have to use function node or some other node. I am not familiar with function node.

Node Temp
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2

This should work in a function node:

const input = msg.payload.split(",")
msg.payload = {}
msg.payload.humidity = parseFloat(input[0].split(":")[1])
msg.payload.temperature = parseFloat(input[1].split(":")[1])

return msg

output:

{"payload":{"humidity":64.4,"temperature":32}}

In the gauge node you can now use {{payload.humidity}}
The gauge node requires a number input, so the % and Celsius was removed.

3

Thank you sir. It really works. Can I know what does the second and third line means? what is msg.payload = {}? I understand the first third line but how do you know the input is 0 or 1 then you split into [1]. I do not understand this particular part. If I can understand, I can try to do on my own in near future for other device also.

4

The input is "Humidity: 64.40%, Temperature: 32.00 Celsius"

const input = msg.payload.split(",") will create an array of 2 elements, each with their own string:

0: "Humidity: 64.40%"
1: "Temperature: 32.00 Celsius"

These strings can in turn be split by the ":" symbol

So input[0] = the humidity string, split the string by ":" and you get another array:

0:"Humidity"
1: "64.40%"

We create a new msg.payload = {} object
We assign a new property "humidity": msg.payload.humidity and assign the value:
input[0].split(":")[1] = "64.40%"

I hope this somewhat clarifies.

5

Thank you sir. I understand now. If I wish to insert chart node, must I use switch node after the function to separate the humidity data and temperature data? Because like Gauge node, we can just use payload.temperature but in chart node, I do not think we can right? Btw thanks for guiding me for the previous question.

6

A Change node, not a Switch node. You are correct in that the Chart must have the value in the payload and can have a line label in the topic. This is so that multiple lines can be plotted on one chart.

7

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