OH3 Serial Binding ......Can you explain to me?

Before switching to OH3 I test my old OH2 sitemaps and there I am on the management of my RFlink in series I succeeded in text mode under VS but with the interface of OH3 I cannot manage with the OH3 serial binding:

I create a thing such as:

At this level if I click on channels I have three options

if I create a chanel linked to a string
we see that the connection is made the string indicates a received frame

All this without creating any serial device !!

Now I have created a Serial device and if I click on chanels this time I have 5 options!

I therefore create a first switch to send commands to my RFLink such

I link an Item Switch on this channel

I create a test page with these Switch and String items

But there the binding of the String is OK but the switch sends absolutely nothing!

What is my mistake?
I managed to do exactly the same thing in text mode under VS
but not through the interface …
and another question why the switch goes back on its own after a few seconds to OFF
thank you in advance

On my phone now, but there is now a (beta) binding available created by someone.
You can find the link here:

If you want to troubleshoot the serial binding, perhaps change the logging to trace status to get some more information from it. Perhaps it gives additional hints.