voidptr posted a pico-OS in the project log forum:
… it is an old silly pico-os (smaller than micro) of coroutines from one on my old projects. This is not fancy or complete like other os or RTOS but it is very small and can be useful…
right now it is written for the PIC p33FJ128GP204, but it can be easily adapted to anything !
Get an assembled web platform for $40, including worldwide shipping.
Via the forum.