AwesomeTTS only supports Anki 2.0.x. The add-on will not work with the newer Anki 2.1.x.
AwesomeTTS makes it easy for language-learners and other students to add speech to their personal Anki card decks. AwesomeTTS supports both on-demand playback and synchronizing audio files with your card deck, making it flexible enough for different needs.
Both Anki and AwesomeTTS are free and open-source software. You can study the source code, make changes, and contribute back to the community.