# How to define Field of TTN uplink node?

**URL:** <https://discourse.nodered.org/t/how-to-define-field-of-ttn-uplink-node/18610>\
**Category:** General\
**Created:** [29 November 2019 13:33 UTC](https://discourse.nodered.org/t/how-to-define-field-of-ttn-uplink-node/18610 "2019-11-29T13:33:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![molly](https://avatars.discourse-cdn.com/v4/letter/m/df788c/32.png) [@molly](https://discourse.nodered.org/u/molly)\
**Post date:** [29 November 2019 13:33 UTC](https://discourse.nodered.org/t/how-to-define-field-of-ttn-uplink-node/18610/1 "2019-11-29T13:33:46Z")

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Hi,  
I am going to make a flow like the following figure 3, which only select humidity or light in the TTN uplink field, but after I setting this, therer has no change in the debug window, the only change was the background of payload.humidity became more dark. However what I want is the output is only the humidity value.  
How can I define the field in TTN field in correct format and how to define the topic in MQTT out to get the downlink message?( The previous topic was molly-pycom-device/devices/orangefipy/down)  
Thanks very much!!!

 ![1](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/8/8e675f15ce8421fc7844ccacc5a74200065d1095.jpeg) ![2](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/8/8e804ec9453f0187a356065d1de61108a3feffa4.jpeg) ![3](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/6/6587f6b5740d68bcbae538eee8064c7c684749bf.jpeg)