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:
This is how all the now defunct Symbian code was compiled.
dlcarrier 4 days ago [-]
It highlights that an idle loop in Arduino is energetically detrimental.
That's not particularly uncommon. Many compilers or OSes default to wait loops when there's nothing to do, and they can be pretty power hungry.
retSava 2 hours ago [-]
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.
mbanzi 4 days ago [-]
The arduino framework is optimised for ease of use. Battery powered devices were not the target back then when it was created. This benchmark should have used one of the many techniques that optimise for power consumption.
maufl 2 hours ago [-]
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
matthiasv 4 minutes ago [-]
Do you have some more background information why it is hard to replicate?
retSava 2 hours ago [-]
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.
SuperMouse 3 hours ago [-]
ESP32 never was good for any powersaving applications.
nottorp 2 hours ago [-]
... but then if you really need to save power you don't use a dev board, or at least disable the parts you don't need on boot and desolder some leds?
snvzz 4 hours ago [-]
As of the recent launch of the ESP32-S31, all the ESP32 product lines have been migrated to RISC-V.
Unsurprisingly, the old, non-standard, encumbered architecture is not missed.
Rendered at 12:45:37 GMT+0000 (Coordinated Universal Time) with Vercel.
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....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.
Unsurprisingly, the old, non-standard, encumbered architecture is not missed.