esptool can't connect but Arduino IDE happily does so
Posted: Thu Feb 05, 2026 4:08 pm
I'm a bit puzzled and sure, I'm missing something but too blind to see it...
I'm using ESP.IDF 5.3.1 on Windows 11 as well as Arduino IDE 2.3.7 to create some small private gadgets.
Somehow I managed to screw up the firmware (partition-table) of my ESP32S-CAM but finally was able to install a simple firmware on it with idf.
Finally I had hoped to clone the firmware of another "fresh" board onto the broken one using esptools.
Unfortunately all my attempts to access (read the flash) the board this way like
esptool.py -p COM3 -b 115200 read_flash 0x00000 0x400000 flash_contents.bin
(also with --before usb_reset) failed with
>>
esptool.py v4.8.1
Serial port COM3
Connecting......................................
A fatal error occurred: Failed to connect to Espressif device: No serial data received.
For troubleshooting steps visit: https://docs.espressif.com/projects/esp ... oting.html
<<
Looks like a cabling setup problem or similar - right?
Interestingly the Arduino IDE happily presents all output of the device in its serial monitor using the same COM port and is even able to upload the device.. (certainly I have stopped the Arduino IDE before trying the esptool).
I'm using the USB2Serial board to connect to the ESP32S.
Any hints would be appreciated!
Cheers
I'm using ESP.IDF 5.3.1 on Windows 11 as well as Arduino IDE 2.3.7 to create some small private gadgets.
Somehow I managed to screw up the firmware (partition-table) of my ESP32S-CAM but finally was able to install a simple firmware on it with idf.
Finally I had hoped to clone the firmware of another "fresh" board onto the broken one using esptools.
Unfortunately all my attempts to access (read the flash) the board this way like
esptool.py -p COM3 -b 115200 read_flash 0x00000 0x400000 flash_contents.bin
(also with --before usb_reset) failed with
>>
esptool.py v4.8.1
Serial port COM3
Connecting......................................
A fatal error occurred: Failed to connect to Espressif device: No serial data received.
For troubleshooting steps visit: https://docs.espressif.com/projects/esp ... oting.html
<<
Looks like a cabling setup problem or similar - right?
Interestingly the Arduino IDE happily presents all output of the device in its serial monitor using the same COM port and is even able to upload the device.. (certainly I have stopped the Arduino IDE before trying the esptool).
I'm using the USB2Serial board to connect to the ESP32S.
Any hints would be appreciated!
Cheers