Chatino keyboard uses Unicode modifier letters for superscript tone markers. For desktop/laptop, the top row of keys on the default layer contain the lower case letters a-m, and the shifted layer has uppercase superscripts A-B, D-E, G-M (there are no Unicode upper case for "C" and "F").
A second layout provides the tone marks via a deadkey on the semicolon position. The tone marks are entered by typing ";", then a key from a-m, which will select the uppercase tone marks. To use the lower case tone marks, simply type ; followed by uppercase A-M.
To type a semicolon, enter ;;
This keyboard also suppots Spanish characters á, é, etc., using the single quote key as a deadkey for the accented vowels and also ñ. To enter ü, use the colon key first, then the u. Uppercase forms are entered with the uppercase letters after the dead key. To enter either the color or single quote, touch them twice.
Chatino mobile uses long press on the keys A-M to select the superscript characters in both lower and upper case forms.
The tone marks are standard Unicode values, which have the advantage over formatting styles because these characters are portable, i.e., they can be used in applications without needing to copy styles. These characters are present in most fonts that support the basic Latin letters, so the text is very portable.
This keyboard was created by Craig Cornelius and Emiliana Cruz for use by the Chatino community of Oxaca and around the world.