You could still use the old SecureBoot; the V3 still supports that and we fixed the issues that made the process glitchable in earlier versions. SecureBoot V2 is a bit more secure (as it uses public/private keypairs for signing the bootloader, meaning it's physically impossible to get the signing ke...

From what I can read online, it's good till 20V, however I can imagine it will burn off too much power if you try that with the load the ESP32C3 gives you... from an AMS1117 (which is in the same package, so the comparison works I think) they give a thermal resistance of 50'ish C/W for the case of t...

You can; it's OK to use input-only pins for input-only functionality. (Thanks for pointing that out, it slipped my mind that CAN has a RX pin before the transceiver.)

(Hm, did you post this question earlier as well? I'd swear I saw it before...) I'm not a secureboot expert, so I'll leave the majority of the questions to my colleagues. I can tell you that technically, 'ROM download mode' refers to any way to (generally) send new code to the ESP32 that is in ROM; y...

No need to look at the GPIO pinout; the GPIO matrix allows you to route any signal of any of the 3 UARTs to any (compatible, so no TX on an input-only pad and not otherwise used by e.g. the internal flash) GPIO. The GPIO pinout does nothing more than effectively tell you the *default* GPIOs for this.

Yes. The only chip we have at this moment which does BT Classic is the (non-C, non-S, original) ESP32.

What IDE is this? Does the IDE flag the code, or does the compiler?

There is, in the form of light sleep, deep sleep, DFS etc. I'm unsure if the Arduino environment supports all of those, though. You could also take a look at the ESP32C3; if you don't need all the ESP32 peripherals that may push the power requirements down a bit lower.

Hm, yeah, then you want to look for something in the direction of the GPIO matrix... not sure if Arduino has dedicated calls for that, but given it's built on ESP-IDF, you may be able to use the esp_rom_gpio_connect_out_signal() call for this.

Sorry, I'm decently sure printf has locks somewhere in the pipeline, but I can't tell you for sure where...