4 ms·

True, so this comes down to the scale of embedded system we're talking about. Typically, the scale of embedded systems runs from very BoM cost sensitive (i.e.

True, so this comes down to the scale of embedded system we're talking about. Typically, the scale of embedded systems runs from very BoM cost sensitive (i.e. making millions of the things), to very cost insensitive (i.e. tens of high value items). Microcontroller-based systems tend to be on the very-cost-sensitive end of the scale due to the fact that if cost isn't an issue, stick a i7 in there instead! If you're cost sensitive regarding the hardware, then you want the most efficient software possible to reduce the hardware requirements, and hence would not want the baggage of a general-purpose OS for a build-time-configured, static system. There are plenty of hardware abstraction layers in the embedded world... (e.g. CMSIS), and familiarity is just a case of what you're used to, that argument could quite easily be turned on its head with a different set of people. IP stacks also exist and are well ported to many RTOSs, (e.g. LwIP). For example, a (very) typical embedded system that would be familiar to a lot of embedded devs would be: - Cortex-Mx (CMSIS for HAL) - FreeRTOS (scheduler) - LwIP (IP Stack) - Eclipse IDE. There are always exceptions to this, e.g human-resources and development time issues change the direction you head in.

fegu 10y ago
In many cases the power usage is important, even for your "few high value" scenario. A small mcu has lower power draw.
pantalaimon 10y ago
I'm not aware of any drivers out there that work purely based on CMSIS, mostly they are vendor specific (e.g. ST will provide drivers for their Chips based on the stm32 HAL, TI will have Tiva based drivers for TI chips, etc.) if they do exist at all. I'd love to see more code reuse here. I agree that nommu Linux is a bit to heavy for most cases as it will always require external RAM and at that point you might as well consider a cheap Cortex-A chip (well, they are not so easy to source/aren't documented as good as e.g. a stm32) but I'd be more than happy if something like RIOT or ChibiOS got more traction.
pjc50 10y ago
BoM cost is not the only cost: the larger your processor, the more complex things like power sequencing, routing to DRAM, boot sequence and bringup, etc. are going to be. Those affect the overall design time and cost even if you're only building one item. I spent a couple of years building a system to run in the "Sierra Wireless OpenAT" RTOS environment (like those ubiquitous SIM900 modules, but you could add your own code to them). It was pretty terrible and I'm glad they now offer modules that run Linux.

fegu 10y ago

In many cases the power usage is important, even for your "few high value" scenario. A small mcu has lower power draw.

pantalaimon 10y ago

I'm not aware of any drivers out there that work purely based on CMSIS, mostly they are vendor specific (e.g. ST will provide drivers for their Chips based on the stm32 HAL, TI will have Tiva based drivers for TI chips, etc.) if they do exist at all. I'd love to see more code reuse here. I agree that nommu Linux is a bit to heavy for most cases as it will always require external RAM and at that point you might as well consider a cheap Cortex-A chip (well, they are not so easy to source/aren't documented as good as e.g. a stm32) but I'd be more than happy if something like RIOT or ChibiOS got more traction.

pjc50 10y ago

BoM cost is not the only cost: the larger your processor, the more complex things like power sequencing, routing to DRAM, boot sequence and bringup, etc. are going to be. Those affect the overall design time and cost even if you're only building one item. I spent a couple of years building a system to run in the "Sierra Wireless OpenAT" RTOS environment (like those ubiquitous SIM900 modules, but you could add your own code to them). It was pretty terrible and I'm glad they now offer modules that run Linux.