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Comment by numlock86 | Hacker News Reader

This:

> allows to apply the advanced techniques used in high integrity systems (i.e. aircraft flight control, medical devices, critical industrial control) to the smallest MCUs used by industry and hobbyists

But also this:

> M2OS implements one-shot non-preemptive scheduling policy

Uhm, what? Those two paragraphs cancel out each other pretty much.

> The STM32F4 board is based on the ARM Cortex-M4 microcontroller. The amount of memory available in this board does not justify the use of a small RTOS as M2OS, however we have decided to port M2OS to this board to explore its implementation on ARM microcontrollers.

STM32F4 is a controller family, not a board. Is this some GPT-3 output?

The list goes on ...

Seriously, what am I even looking at? Is this just some SEO optimized site with a bunch of buzzwords and some seemingly valid content?

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It likely refers to the popular STM32F4 Discovery board [0], which is a devkit for that family of uCs. Good for prototyping, has an onboard programmer and everything. It has 1MB of flash, so I think this line means "if you wanted to use this board, you'd be better off with a full RTOS that can make use of that code space, rather than M2OS which is optimized for single-kB flash sizes".

The rest of your comment I agree with. It seems to be a half-baked academic project. Might be interesting if you know anything about Ada, which I don't.

[0] https://www.st.com/en/evaluation-tools/stm32f4discovery.html

The Software engineering and real-time group at the Universidad de Cantabria seem to be pretty well credentialed in this area. They produced a viable RTOS some years ago called MarteOS ( https://marte.unican.es/ ) This is no small feat.

That had me scratching my head too. I have a board next to me based on the STM32F407, which is the same MCU as the Discovery board (we prototyped on the Discovery board actually) and it definitely has the capability to run an RTOS.

I interpreted it the other way: it has too much RAM to justify a micro-OS.

Also:

> smallest MCUs used by industry and hobbyists

> ARM Cortex-M4

Hardly the smallest MCUs used.

That core is a mainstream choice for safety-critical embedded systems these days. Usually running in a lockstep configuration of course, unlike some of the boards discussed here.

They claimed it was an OS for the smallest MCUs in use, though, not just for mainstream ones.

What particular concern do you have with the scheduling policy? As I understand it, it's an RTOS for embedded devices. They're most likely just referring to SPARK's formal proofing.

As for the STMF4, they're possible referring to the STMF4DISCOVERY boards.

If you look at ST's product chart page, STM32F4XX microcontrollers can have anywhere from 512K to 2056K of flash, maybe they're suggesting that 512K doesn't justify the use of small rtos?

It can be as low as 64K in the case of the STM32F410 but I can't tell whether it would be supported.

While I am aware of the technical specs, my point is about the wording itself. This was just an example. The "Docs" section for example doesn't actually hold any documentation.

Something about this website feels uncanny, hence my (joking) guess regarding GPT-3.

They're probably talking about boards like this that also have megabytes of SDRAM. https://www.st.com/en/evaluation-tools/32f429idiscovery.html

It's usually not the amount of flash that's the problem with an RTOS on an embedded microcontroller. It's the amount of RAM. Because each process requires it's own stack. That said STM32 parts generally have enough.

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