MQTT JSONPath Transformation to extract values from multiple DS18B20

Add-ons Bindings
1

Hello Folks,

I am a silent reader sice few months.
My home automation is growing week by week. A lot of function I could implement by using this forum or other sources.
But now I am at a point where I need some support from an expert.

I am using a nodeMCU with tasmote FW and 3 DS18B20 Temp. Sensors.
All the sensors are connected to one GPIO.

So the MQTT topic contains all three sensors in it. All the have different temperatures to display.
An somehow I have to extract the right sensor and display it to the right value.

The topic looks like this:

{“Time”:“2019-11-04T17:35:16”,“DS18B20-1”:{“Id”:“011563F25DFF”,“Temperature”:13.8},“DS18B20-2”:{“Id”:“031674B309FF”,“Temperature”:34.6},“DS18B20-3”:{“Id”:“0416747EBDFF”,“Temperature”:43.9},“TempUnit”:“C”}

Question: How does the transformation look like that I can extract each temperature value?

Thanks a lot in advance.
BR, KarMa

Extract temperature from an MQTT string
2

First in the tasmota console do:
setoption64 1

See: GitHub - arendst/Tasmota: Alternative firmware for ESP8266 and ESP32 based devices with easy configuration using webUI, OTA updates, automation using timers or rules, expandability and entirely local control over MQTT, HTTP, Serial or KNX. Full documentation at
This will change the - into an _ for the DS18B20s

Then the transormation is:
JSONPATH:$.DS18B20_1.Temperature
etc…

Make sure you install the JSONPATH transform!!

2 Likes
3

Thanks for the quick reply and the >setoption64 1
hint.
I looks like that I got also an issue with the connection from MQTT to Openhab.
Let me first solve this, than I continue witht the transformation.
Thank you!

4

Hi KarMa,
did you solve your issue and get it working with 3 x DS18B20.
I had it working with one sensor and the following;
transformationPattern=“JSONPATH:$.DS18B20.Temperature”
and it worked.
After vzorglub’s correction I did setoption64 1 and I now have underscores in stead of hyphens but the following only shows “-” on my sitemap.
transformationPattern=“JSONPATH:$.DS18B20_1.Temperature”

1 Like
5

Solved my problem. See my other thread on extracting temprature from mqtt string.
I used the sensor id rather than DS18B20_n as the numbers can change automatically if one is disconnected.