[hwh]

It is all a question of use case. This reply comes up all the time when I talk about how I use microcontrollers and what I use them for. For myself, microcontrollers offer me maximum control with minimum overhead. No OS, or maybe just some RTOS that does not really "boot" except for copying initial values for variables from Flash into RAM, being done in a fraction of a second. Switch it on, off it goes. Interfacing with SRAM and Flash without a driver.

You can do MCU based PCB designs. It gets harder when it comes to the mentioned Cortex-A. It will be harder to sample, say, 40 pieces of them. You're very much supposed (and better off) to buy boards like OrangePi or similar.

ESP designs, especially ESP32, are somewhat in between. Started off as a little documented blackbox with a RTOS interface it is now a much better (but absolutely not on par with Cortex-M designs) documented platform. However, part of it is still a proprietary code blob. They are beefy beasts, however, and when you need just that - well, it's a no-brainer. I just wish they were documented like STM32s plus ARM manuals and had a little more toolchain support. The price tag keeps me from complaining any louder.

When you don't really have hard constraints and are fine with a 5 second bootup, chose whatever fits your bill. When exact timing is an issue (and you don't want to go bare metal on the Cortex-A), when fast bootup is an issue, well - better look at MCUs.

[0xbear]

Not gonna argue with that. I do use MCUs myself where appropriate. I like that they’re more hardware than software: flash the thing once and it will work every time from there on out. Very few moving parts, everything is very simple, power consumption is measured in milliwatts.

But it still blows my mind that the equivalent (a vast superset, if you consider the GPU and specialized coprocessors) of my workstation from the late 90s now costs less than $5.