How to get and post weight from weighing scale

I am trying to get weight off a scale using link or button. I want to be able to get weight using web server (I got Puma using Ruby gem), save that weight in a database SQLite3 (ruby gem), display it using json.

I installed Puma and SQLite3. Already got code that allows user to enter weight manually in a form, but want to get weight off scale automatically. I created a helper class with get and post methods and using it in weights controller and used it in the form where link is being used.

Does anyone have ideas how and what's the best way to code it?

Thanks