Sending float to Arduino via ue4duino

Hi everyone,

this is my first post. I started learning UE some days ago so please be gentle;)
If my post is in the wrong category I will be more than thankful if some of you could change it!

My problem is the following:
I try to sent a float via blueprint to ardiuno.

I can set up the connection and it seems to work with the defeined sketch.
This is how my setup look like:

Arduino doesnt seem to get the float.
I am be more than grateful for every hint!

Have a nice weekend!