Speech to text conversion


I am looking for an app that takes audio input from UART and give text output i.e., identify any speech in the audio input, transcribe that to text output. So I want to know, if someone has experience in this, can you recommend me a good and easy way to setup a voice recognition system?

The idea is to take input through voice and to get a result that you can handle. For example saying “Hi how r u” could generate the response in text display “Hi how r u”.