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Comment by joezydeco | Hacker News Reader

After seeing this I think the Amazon AWS/FreeRTOS combo is looking like the better architecture for a node solution. FreeRTOS can run on lowly M3s at 120Mhz, like the LPC2478.

A 500MHz A7 part is way too much silicon for an IoT node. How much external SDRAM and Flash are connected to that MediaTek core?

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You call 120MHz lowly? I call that luxury! I am working on a product where we're running an M4 way below 1MHz. And our hardware guys have me counting bytes in software...

FreeRTOS is a pretty good fit for this situation. I am only disappointed that newlib is so ridiculously huge in comparison. Some functions in there are twice the size of FreeRTOS.

I typically wouldn't, since I grew up working on 1MHz 8-bit cores. But working with some of these tiny M0 and M3s, there's nothing slower than 60-120MHz now.

Well, these parts can almost always go much slower than that if you need to save power. Our hardware engineers want to because they reall, really, really do not want to provide the extra few uA for an extra half MHz or a few extra bytes of Flash. Which means I am stuck counting bytes and cycles like it is 1980 all over again.

Not saying this isn't fun, but don't tell my boss ;).

> After seeing this I think the Amazon AWS/FreeRTOS combo is looking like the better architecture for a node solution. FreeRTOS can run on lowly M3s at 120Mhz, like the LPC2478

Is that supposed to imply linux can't? Or that linux plus a GNU subsystem can't? I've personally run it on a lot lower end hardware than that seems to be.

The Cortex M series is prolific but lacks a proper memory management unit which makes running Linux an iffy business. FreeRTOS is by far the most dominant player in this space.

Different markets really, sounds like Microsoft is targeting items like internet connected cameras (think Mirai endpoints). Where as Amazon is targeting low power prolific devices, eg. IoT buttons.

Oh, it can. I've run ucLinux (MMU-less Linux) on an LPC1788 (Cortex-M3) and it works...okay. Making dynamic libraries work correctly on it is a pain in the ass. It just wasn't worth it at the end and the O/S hogged up most of the processor, RAM, and Flash.

Exactly. I think these end up as good PoCs - and it would be amazing to think of a future where we can run one of the Linux derivatives on a something that was designed with FreeRTOS or equivalent in mind - but it's just not going to happen on a commercial scale in my opinion.

ARM Linux isn't really slimming down, so the chips need to grow to catch up.

You're starting to see devices like the Renesas RZ/A1H that has 10MiB of SDRAM on the die and can boot Linux out of a single cheap QSPI memory part.

> Is that supposed to imply linux can't?

Regular Linux can't. uCLinux might.

Since late 2.5.x, uCLinux has been more or less mainlined.

You can run regular Linux on these, you just probably don't want to.

FreeRTOS is interesting and useful, but also requires knowledge of the device you are running on as well as implementing drivers. Having done a project involving FreeRTOS, compilation flags need to be customized to the platform one is dealing with.

Which should be alright, as IoT implies designing both hardware and software.

You've just described embedded systems engineering.

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