List of Open Source Real-Time Operating Systems • Hacker News Board

Re: List of Open Source Real-Time Operating Systems

#31

Post by monocasa » Sat, Feb 09, 2019, 5:17 PM UTC

BaalZebub wrote: post #24

Isn't TempleOS RTOS?

It's too bad you're being downvoted. It's a legitimate question.

Looking at the source, a case could be made either way IMO. On one hand the scheduler doesn't have priorities, but on the other, you have to explicitly pin tasks to cores so you could actually guarantee real time behavior pretty easily on a fixed platform...

Re: List of Open Source Real-Time Operating Systems

#32

Post by sedachv » Sat, Feb 09, 2019, 5:47 PM UTC

rambojazz wrote: post #4

Can Linux itself be compiled/built as a realtime OS? I mean without adding additional software or hacking.

One of the reasons why Linux is not suitable for real-time use is virtual memory. It's not even about swapping. The Translation Lookaside Buffer introduces too much variance into timing. Same thing with instruction and data caches and even instruction pipelining. It's not just Linux, but most general-purpose CPUs that are not suited for real-time control applications.

Re: List of Open Source Real-Time Operating Systems

#33

Post by applesvsoranges » Sat, Feb 09, 2019, 6:46 PM UTC

jhallenworld wrote: post #25

Is TI-RTOS really not in development? It's the OS TI gives you when you download their tools. TI is weird, they have their own C compiler.

Yeah. I used TI-RTOS a couple of years ago for some work and the whole experience was very different. The most unique part was that the RTOS came bundled with a development GUI integrated into the IDE where you could create threads, mailboxes and other such RTOS primitives. I don't think I liked using it very much though.

Surprised to see that they killed the project.

Re: List of Open Source Real-Time Operating Systems

#34

Post by pantalaimon » Sat, Feb 09, 2019, 7:03 PM UTC

jhallenworld wrote: post #27

One way to deal with the many available operating systems is to use OSAL. It's an abstraction layer for embedded OS (and POSIX). Admittedly I have mixed feelings about it since it creates work when debugging in a new OS: you need to trace which OS call OSAL is using.

But the RTOS is already an abstraction layer around the hardware, how would adding another abstraction possibly help?

It's not like you often find yourself in the situation where you want to run the same application on multiple RTOSes, it's usually way too specific to the device.

Re: List of Open Source Real-Time Operating Systems

#35

Post by pantalaimon » Sat, Feb 09, 2019, 7:05 PM UTC

rambojazz wrote: post #4

Can Linux itself be compiled/built as a realtime OS? I mean without adding additional software or hacking.

It's currently not possible to compile Linux to something that works with 64k RAM and similar amounts of flash like what you usually would find on a MCU.

Re: List of Open Source Real-Time Operating Systems

#36

Post by scottlocklin » Sat, Feb 09, 2019, 7:22 PM UTC

I'd be curious how many of these actually provide real time guarantees the way QNX or VxWorks does. I think quite a few of them may simply be "embedded OS" rather than RTOS.

Re: List of Open Source Real-Time Operating Systems

#37

Post by naasking » Sat, Feb 09, 2019, 8:08 PM UTC

pantalaimon wrote: post #34

jhallenworld wrote: post #27

One way to deal with the many available operating systems is to use OSAL. It's an abstraction layer for embedded OS (and POSIX). Admittedly I have mixed feelings about it since it creates work when debugging in a new OS: you need to trace which OS call OSAL is using.

But the RTOS is already an abstraction layer around the hardware, how would adding another abstraction possibly help? It's not like you often find yourself in the situation where you want to run the same application on multiple RTOSes, it's usually way too specific to the device.

> It's not like you often find yourself in the situation where you want to run the same application on multiple RTOSes, it's usually way too specific to the device

Perhaps that's the point: make your program more portable across different hardware that may only support specific OSes.

Re: List of Open Source Real-Time Operating Systems

#38

Post by magnetic » Sun, Feb 10, 2019, 12:10 AM UTC

The first entry FreeRTOS shows MIT as license, but says it's distributed as GPL in the description. I don't know where they got the GPL part from: it's not mentioned anywhere at https://www.freertos.org/a00114.html

Re: List of Open Source Real-Time Operating Systems

#39

Post by kqr2 » Sun, Feb 10, 2019, 2:47 AM UTC

magnetic wrote: post #38

The first entry FreeRTOS shows MIT as license, but says it's distributed as GPL in the description. I don't know where they got the GPL part from: it's not mentioned anywhere at https://www.freertos.org/a00114.html

From https://aws.amazon.com/freertos/pricing/ :

The Amazon FreeRTOS operating system and software libraries are released under the MIT open source license, a permissive license with limited restrictions on reuse.

Re: List of Open Source Real-Time Operating Systems

#40

Post by tesseract » Sun, Feb 10, 2019, 4:33 AM UTC

magnetic wrote: post #38

The first entry FreeRTOS shows MIT as license, but says it's distributed as GPL in the description. I don't know where they got the GPL part from: it's not mentioned anywhere at https://www.freertos.org/a00114.html

FreeRTOS used to be dual-licensed GPL (with an LGPL-esque linking exception) and commercial. Amazon acquired the copyright in 2017 and relicensed FreeRTOS under the MIT license.