Ok I think I worked it out. I used the ESP32-S3R8 chip, which I have just realised doesn't have internal flash, and so perhaps the behavior we are seeing makes sense as there is no flash chip in the system - as that's where the error occurs. Looks like someone else had a similar experience ( https:/...

My goal here is to be able to flash my custom PCB, which I have not been able to do yet. I had thought that I could use USB jtag on the esp32s3 board to get it into 'download mode'. If I run this python code snippet, implementing the approach in section 33.4.2 of esp32s3 TRM v1.4: with serial.serial...