more direct access to characteristic data

[ccutrer]

Pull Request Checklist

Please confirm that you've done the following when opening a new pull request:

• [x] For fixes and other improvements, please reference the GitHub issue that your change addresses.
• [x] For fixes, optimizations and new features, please add an entry to the CHANGES.md file.
• [x] Run mvn compile before committing, so that the auto-code formatter will format your changes consistently with the rest of the project.