Developing a non-x86 Operating system

Question

I have to choose a thesis topic soon and I was considering implementing an operating system for an architecture that is not x86 (I'm leaning towards ARM or AVR). The reason I am avoiding x86 is because I would like to gain some experience with embedded platforms and I (possibly incorrectly) believe that the task may be easier when carried out on a smaller scale. Does anyone have any pointers to websites or resources where there are some examples of this. I have read through most if not all of the OSDev questions on stack overflow, and I am also aware of AvrFreaks and OSDev. Additionally if anyone has had experience in this area and wanted to offer some advice in regards to approach or platform it would be much appreciated.

Thanks

Answer 1

Contiki might be a good thing to research. It's very small, runs on microcontrollers, and is open source. It has a heavy bias towards networking and communications, but perhaps you can skip those parts and focus on the kernel.

Answer 2

Developing an (RT)OS is not a trivial task. It is very educational though. My advice to you is to start hardware independent. PC is a good starting point as it comes with plenty of I/O possibilities and good debugging. If you create a kind-of-virtual machine application, you can create something with simple platform capabilities (console output, some buttons/indicators are a good start). Also, you can use files for instance, to output timing (schedules) If you start on 'bare metal' you'll have to start from scratch. Debugging on a LED (on/off/blinking) is very hard and time consuming. My second advice is to define your scope early: is it the scheduler, the communication mechanisms or the file systems you're interested at... ? Doing all can easily end up in a life long project.

Samek, Miro, Practical UML Statecharts in C/C++ contains some interesting sections on a microkernel. It's one of my favorite books. Advanced PIC Microcontroller Projects in C: From USB to RTOS with the PIC 18F Series seems to cover some of your interests; I haven't read it yet though. Operating Systems: Internals and Design Principles may also bring good insights. It covers all aspects from scheduler to network stack. Good luck!

Answer 3

If you choose ARM, pick up a copy of the ARM System Developer's Guide (Sloss, Symes, Wright). Link to Amazon

Chapter 11 discusses the implementation of a simple embedded operating system, with great explanations and sample code.

Answer 4

Seems like you should get a copy of Jean Labrosse's book MicroC/OS.

It looks like he may have just updated it too.

http://micrium.com/page/press_room/news/id:40

http://micrium.com/page/home

This is a well documented book describing the inner workings of an RTOS written in C and ported to many embedded processors. You could also run it on a x86, and then cross compile to another processor.

Answer 5

ARM and AVR are chalk and cheese - you've scoped this very wide!

You could produce a very different and more sophisticated OS for ARM than AVR (unless you are talking about AVR32 perhaps - which is a completely different architecture?).

AVR would be far more constraining to the point that the task may be just to trivial for the scope of your thesis. Even specifying ARM does not narrow it down much; low-end ARM parts have small on-chip memories, no MMU and simple peripherals; higher end parts have an MMU, data/instruction caches, often a GPU, sometimes an FPU, hardware Java bytecode execution, and many other complex peripherals. The term 'ARM' covers ARM7, ARM9, ARM11, Cortex M3, Cortex M8, plus a number of architectures intended for use on ASICs and FPGAs - so you need to narrow it down a bit perhaps?

If you choose ARM, take a look at these resources. Especially the Insider's Guides from Hitex, and the "Building bare-metal ARM with GNU", they will help you get your board 'up' and form starting point for your OS.

Answer 6

The first thing I recommend is to narrow your thesis topic considerably. OSs are ubiquitous, well researched and developed. What novel idea do you hope to pursue?

That said, the AvrX is a very small microkernel that I've used professionally on AVR microcontrollers. It is written in assembly. One person started to port it to C, but hasn't finished the port. Either finalizing the port to C and/or making a C port to the AVR32 architecture would be valuable.

Answer 7

An OS shall not be tightly coupled to any processor so ARM or x86 doesn't matter. It will be a bigger topic, if we start discussing if ARM is embedded and x86 is not. Anyway, there are many many places in which x86 processors are used for embedded software development.

I guess most of the kernel code will be just plain C lanugage. There are many free OS that are already available, like for example, embedded linux, Free version of Itron, minix, etc ... It will be a daunting task.

But on the other hand, what you can try is, port embedded linux to platforms in which it is not yet working. This will be really useful to the world.

Answer 8

Silly as it may sound, I was recently interested in the Arduino platform to learn some hacking tricks with the help of more experienced friends. There was also this thread for a guy interested in writing an OS for it (although not his primary intention).

I think the Arduino is very basic and straightforward as an educational tool for such endeavors. It may worth the try checking it out if it fits the bill.

Answer 9

An RTOS is almost never architecture specific. Refer to any RTOS architecture available on the net and you will notice that a CPU/Hardware abstraction layer abstracts out the CPU. The board specific portions (that deal with peripherals such as com ports, timers etc.) are abstracted by a board support package.

To begin with, get an understanding of how multi-threading works in a RTOS try implementing a simple context switch code for the CPU of your choice; this will involve code for creating a thread context, saving a context and restoring a saved context. This code will form the basis of your hardware abstraction layer. The initial development can easily be accomplished using a software simulator for the selected CPU.

I agree with the poster who suggested reading the book, uCOS-II by Jean Labrosse. Samples of context switch code, especially for x86, should be just a google search away!