Best reference to start writing a very basic RTOS from scratch

Question

I wish to write a very basic RTOS which can just switch between two tasks. Its not for any professional usage. Its just for fun

Most references say about how to use an RTOS and not about how to write one.

Refering an opensource RTOS like FreeRTOS will not make us understand the base concept.

One reference i found is Simple Real Time Operating Sysytems

I would wish to know if there is any other source which can be a kickstarter for those who wish to write an RTOS from scratch.

Answer 1

Jean Labrosse's book MicroC/OS-II:The Real Time Kernel describes the implementation of a simple RTOS in minute detail. There is a new edition for MicroC/OS-III, with architecture specific editions (but I've no experience of the new edition, and MicroC/OS-III is has slightly more complex/sophisticated scheduler).

Although now a commercial RTOS in its own right MicroC/OS was originally presented by this book (and its µC/OS predecessor) as a reference on RTOS kernel/scheduler implementation. Its principles can be applied more broadly to implement your own RTOS (though you need to respect any licences and copyrights of course).