ITC Forth in C, built and tested on the Adafruit QT Py and on the Adafruit Itsy Bitsy M0.
This is a target compiled Forth that deviates from the standard in several ways. Branching words don't consume the stack. This is similar to the Green Arrays chips.
There are two address spaces, RAM and program memory. RAM has an address "register" called A. Program memory has one called P. Primitives such as c@+, c!+, @p+, use those address registers. Also it's target compiled but not exactly tethered. The target has separated heads and a text interpreter, but no compiling. At least not yet.
The interpreter is specifically designed to work with the Arduino IDE and its serial terminal.
See the file "main.fs" for a steno keyboard firmware.