Hi @ll,

I found the problem for myself. I gave the power over the USB-Port. After support the ESP32 with power from serial interface board, everything worked perfect. Thanks to Agnus.

Can close the thread.

Sorry for the delay. I have tested it. The lines are not connected anywhere. I am not sure, but I think it RX and TX are connected it would cause problems with the handshaking at all. After watch ing the code of the esptool.py script it requires the esp32 send the same datas back, but the following ...

Hi @ll, I am using a custom FCB board with a ESP32 Pico D4 chip. I get a serial connection over UART0 to the ESP32 and if I set GPIO0 to GND it starts in Download Mode and returns: rst:0x1 (poweron_reset),boot:0x3 (download_boot(uart0/uart1/sdio_rei_reo_v2)) waiting for download But after, the ESP32...