[SOLVED] MQTT 2.4 transformations error

Add-ons Bindings
1

After much trial and error I have managed to get MQTT 2.4 updating a string item,

  1. Added a MQTT broker Thing pointing to my mosquittto mq
  2. Added a MQTT generic Thing using the Thing from 1 as the bridge
  3. Added a Channel to (2) selecting the MQ topic I want to catch
  4. Linked (3) to the item I want to receive the value

in the events log with a string item an no transformation I see

test_solar changed from NULL to <msg><time>2018-12-24 16:03:21</time><tmpr>20.2</tmpr><ch1><watts>00672</watts></ch1><ch2><watts>00028</watts></ch2></msg>

If I then add XPATH transformation on the channel definition XPATH:/msg/ch1/watts/text() I get

`test_solar changed from 2018-12-24 16:03:2120.20067200028 to 00658

… however I want the item to be a Number. If I just change the item type to number then I get

Tried to set invalid state 00658 (StringType) on item test_solar of type NumberItem, ignoring it

so I changed the XPATH to XPATH:/msg/ch1/watts/number(text()) which according to an online XPATH tester should return a Double=‘658’ but instead I get

Executing the XPATH-transformation failed: transformation throws exceptions

Can someone enlighten me on how to convert my string of numbers to an actual number ?

Thanks in advance

2

Is it a text channel or a number channel?

3

Thank you so much Vincent that was the problem, editing the channel to change the transformation doesnt give the option of changing the channel type so it was still a string. Deleted and recreated as a number type and now the transform works as expected :grin:

I spent a couple of hours looking at that and never spotted it.

4

Please mark the thread as solved, thanks
Merry Christmas