At the end of this topics i would like to thank you to @arjanvanb for the useful advices and i would like to make short digest to be useful for the someone else also.
Here is the highlights:
- documentation on “Payload functions” is here Is there any documentation on payload functions?
- before you send the data from the node you should pack it in packet as small as possible due to stay within fair policy BW use; so the best way is to code it and not to use for example ASCII text;
- one nice tools to code/decode on Arduino/TTN is https://github.com/thesolarnomad/lora-serialization
- to code use code for Arduino and if you use “Convenience class LoraMessage” do not forget “LoraMessage message” at the beggining of the loop, otherwise your payload will grow every time as it will pass the loop ;-);
- to decode message on TTN go to console/payload functions and in window of decoder copy src/decoder.js and at the end add for example “return decode(bytes, [uint16, temperature, humidity, uint16], [‘voltage’, ‘temperature’, ‘humidity’, ‘pressure’]);”
I hope this will make a day to someone else 