Setting compiler optimisation to 'Size', log level to 'None', and assertions to 'Silent' should get you most of the way there. Enabling nano formatting options also helps a lot iirc (uses printf in ROM so you don't need it linked in your binary). Also see: https://docs.espressif.com/projects/esp-idf...

Station config has fields to control how the driver should select the best AP:
https://github.com/espressif/esp-idf/bl ... #L386-L387
Or you can use custom logic and specify the BSSID.

Yes, this is documented behaviour affecting 36 and 39. Look up the ESP32 errata document for details. I wouldn't have expected it to trigger continuously though, only once on initialisation when the ADC is powered up. Are you using automatic light sleep, or manually disabling and enabling BLE period...

Why does an image only containing printf("hello world") (and some very basic wifi) take almost 1 MB of space on the flash. ESP-IDF'S default config generally favours development-friendly options over release optimisations. A project as you've described, aggressively optimised for size, should be al...

I haven't used a C3 specifically but 6mA is very suspicious. That says to me that it's not booting correctly. I know from experience that the ESP32 can sometimes be stuck drawing about this much with a bad boot (eg. if EN is high from my attached ESP-PROG before 3V3 applied). The lipo is also potent...

Schematic?

Are you sure your monitor config is correct? Correct port selected? Do you get output from a known-good board?

Can you use an ammeter to confirm ~0mA when EN is low and ~20mA when released high?

With NOR flash, writes can only set bits to 0. Erase commands must be used to reset all bits to 1.

Ordinarily you'd erase the sector (or block) before writing to it, otherwise trying to write any bits 0->1 will have no effect.

It seems your byte at 0x100001 is already 0x00.

What you're seeing is the "idf_ver" field of the esp_app_desc_t. You can read about the image format here: https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/app_image_format.html There's also a section in there on adding your own custom header after the esp_app_desc_t.

Could you use a very high priority task? The priority will ensure it won't be waiting on other tasks, and this way you can avoid the limitations of doing this in an ISR. From memory there's a configuration field in RMT TX initialisation for the idle_level which should keep the output high when inact...

Yes a voltage divider is the usual route. My suggestions were unorthodox but they had their merits. Voltage divider will do fine.