The z88dk is a collection of software development tools that targets the 8080 and z80 family of machines. It allows development of programs in C, assembly language or any mixture of the two. What makes z88dk unique is its ease of use, built-in support for many z80 machines and its extensive set of assembly language library subroutines implementing the C standard and extensions.
For the z80, z180 and z80n CPUs a port of freeRTOS v10.3.0 has been created.
The header files are present within the included files for the newlib.
As freeRTOS is mainly written in C, the library will not be included directly into the z88dk repository. The freeRTOS library can be installed from feilipu/z88dk-libraries/freertos.
Currently two targets (4 boards) are supported.
Further work will support the Spectrum Next.
Additional targets are easily supported by modifying the macros within the Board Definitions header file.
For background reading, the process of getting RomWBW HBIOS supported on SCZ180 is available here.