Erik -

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8 years, 4 months ago.

When to use mbed OS 5

Now mbed OS is available in the online compiler, the main question I would ask is: Why? Why should I use mbed OS 5 instead of classic mbed? If I look at some documentation and by checking it in the online compiler it seems mainly that many libraries are built-in, but I don't know if one giant library offers me advantages. I guess if you want to focus on (some specific forms of) networking connectivity it certainly offers advantages. But if I want to make lets say a quadcopter, or a BLE watch, etc, does mbed OS offer me any advantages?

The blinky example already takes double the flash and ten times the SRAM on an LPC1768 compared to a basic one. Although I guess/hope that is mainly due to RTOS (still of course if you don't need RTOS it is quite a bit).

Maybe I am mistaken, but to me it seems mainly like many more libraries in the classic mbed one, and if you don't need those it is of limitted value. But I am happy to be proven wrong :).

Btw1: Mbed-os has some files in the online compiler which aren't really useful, like a picture and a CLI readme.

Btw2: If you go to developer.mbed.org your entire screen will be filled by a single banner.

Btw3: While technically the LPC1114 is apparently mbed enabled, the blinky example takes 70% of its flash and 50% of its SRAM.

Question relating to:

Last updated: 05 Aug 2016
mbed, OS

1 Answer

Simon Ford
8 years, 4 months ago.

Hi Erik!

As you rightly point out, mbed OS 5 is fully integrating these RTOS, connectivity and security components as part of the maintained core, so they are all developed, integrated and tested together such that they can become relied upon and official parts of the OS - so things like Ethernet, BLE, WiFi, 6LoWPAN and Thread, TLS security. They are still componentised within that core, so they don't need to be "enabled" and built in to the end image.

So sure it will make sense to build a BLE watch with mbed OS 5, even if it is not using some of the features. In fact, we'd like to ensure there is no reason not to upgrade from classic mbed to mbed OS 5 in most cases, and this is what we expect to happen. Hopefully you can help us refine things to make sure that is the case.

At the moment, on some very small applications you'll notice some code size jumps mainly due to us using the standard C libraries rather than the "microlib" or "nanolib" variants for builds; this is due to them not yet having the hooks for thread safety in we want, but they are being worked on.

Thanks also for all the BTWs! I'll get someone to look at those.

Simon

Accepted Answer

Simon,

Given Erik's observations is mbed OS5 compatible with targets with smaller flash sizes? Such as the ones which currently are documented to be incompatible due to program size with the previous version of mbed OS. I'm referring specifically to STM32 targets such as the L031K6 which have 32kB flash and according to the platform documentation are not compatible with mbed OS (or OS3 I guess following the new naming convention).

Krzysztof

posted by Krzysztof Sitko 06 Aug 2016

Thanks, another question: Is OS5 build on top of mbed classic, or do they not share their source code?

In general I think I agree with Krzysztof, regardless if it has no direct disadvantages, on small targets the memory overhead of RTOS is going to be a problem.

posted by Erik - 06 Aug 2016

Hi Erik - mbed OS 5 and mbed classic share the same codebase. https://github.com/ARMmbed/mbed-os

posted by Sam Grove 06 Aug 2016

Another small additional question in this regard: If i include mbed-os instead of mbed into my program but just only include mbed.h and NOT rtos.h in my main.cpp, will i still suffer from some flash and/or memory overhead or will the compiled result be comparable with mbed 2.0?

Nenad

posted by Nenad Milosevic 08 Aug 2016

Worth reading here on when to use mbed OS which is now available in the online compiler. And thanks for providing here best answer of it.

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