So how do you reboot into your app while preserving the memory? Esptool would normally do a hard reset. Put a call to a rom restart function at the beginning of the binary and let it execute? Use rtc ram and mark it as noinit in your app?

Well the additional on device code could just be (open uart, write data to memory location). The rest of the code could be the same. So the attackers will be able to sniff WiFi at the factory and crack wpa2 psk or eap but not have the ability to compromise the provisioning machine? With esptool by d...

Is encoded null terminated and do you have enough free memory for it and does cjson support giant strings?

You said you are expecting two events, which two? What are you sending? CHAR idle CHAR? I would guess the idle time is measured from the rising edge of the stop bit to the falling edge of the next start bit.

It's probably doable with some mods to esptool but you have to choose a ram area that the app is not going to use or init. Why not have the app check if it has been provisioned and if not, reopen the serial connection to get the provisioning data from the programmer? Or do it via WiFi so you have a ...

https://docs.espressif.com/projects/esp ... oning.html

https://docs.espressif.com/projects/esp ... ocomm.html

Use a flag/semaphore but is there a way to check if tx is done in the Arduino rmt driver?

There are very few unused pins, you probably have to use uart0 programming pins for the pir.