Yes, TFA article says they never activated any power-saving, so the idle loop is more or less just staying in active mode, which has the same power consumption as doing calculations.
But one thing the article didn't point out is what hardware peripherals each firmware activated by default. Eg, activating UART might use default pins and activate an UART RX on a pin, which might incur a mA-order penalty. Hence, a useful first step in optimizing power is to identify what functionality you need and ensure all else is always powered down (eg uart rx, clocks and timers, radio peripherals.
One problem with -O3 is that it disregards any effects of the cache (and yes, ESP32s have a bit of cache memory). I recommend using -Os as the default optimization level, as it often has the same or almost the same performance benefits as -O3. Less cache pressure is beneficial, especially for bigger applications, and the smaller code size is of course nice on embedded systems that have limited amounts of flash storage. If you know some specific functions or source files are performance sensitive, you can use pragmas to change optimization for those:
As an off-topic remark, I've used the qoitech arc power analyzer quite a bit and it's quite nice and easy to use, when your DUT is <5V and low amps. There's also the Nordic PPK2 kit, which is cheaper but I haven't tried it. Both are aiming at the crowd that prefers a simple, handles-most-use-cases, little USB-connected box that runs the client on your computer, rather than a separate bulky thing with screen and whatnot. Trade-offs of course though.
I did something similar, but less scientific, comparing ESP-IDF and esp-hal (Rust). Unfortunately I learned that the optimizations that are already in ESP-IDF (most of all automatic light sleep between BLE advertisments) are hard to replicate in Rust/esp-hal/embassy and so for battery powered devices you might want to stick to C++/ESP-IDF
Hmm, those are some worrying news for Zephyr, but also for Linux. For reasons that escape my full understanding, a lot of embedded hardware needs Linux to work. If Zephyr, which I bet has been carefully crafted for microcontrollers, leaves some unnecessary things on, who knows what even an extremely trimmed down Linux running in, say, the beagle board, gets away with.
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[ 0.25 ms ] story [ 11.1 ms ] threadBut one thing the article didn't point out is what hardware peripherals each firmware activated by default. Eg, activating UART might use default pins and activate an UART RX on a pin, which might incur a mA-order penalty. Hence, a useful first step in optimizing power is to identify what functionality you need and ensure all else is always powered down (eg uart rx, clocks and timers, radio peripherals.
Unsurprisingly, the old, non-standard, encumbered architecture is not missed.
One problem with -O3 is that it disregards any effects of the cache (and yes, ESP32s have a bit of cache memory). I recommend using -Os as the default optimization level, as it often has the same or almost the same performance benefits as -O3. Less cache pressure is beneficial, especially for bigger applications, and the smaller code size is of course nice on embedded systems that have limited amounts of flash storage. If you know some specific functions or source files are performance sensitive, you can use pragmas to change optimization for those:
See https://gcc.gnu.org/onlinedocs/gcc/Function-Specific-Option-.... Clang has a similar pragma, see https://clang.llvm.org/docs/LanguageExtensions.html#extensio....