ESP8266 Community Forum

Always have such a output on my serial output, regardless of the sketches. Even using the Blink sketch with only one Serial.println line.
Any idea? I have used fresh unprogrammed ESP-01 boards.

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Blink example started

Looks like the output from the bootloader. As far as I can tell, it cannot be disabled.

Okay. What a pity. It is disturbing the output. Another question , why is the esptool uploading two parts? First th address 0 part and then the second part of the same sketch. Could you please explain.

As a workaround, if you need clean UART output, you can swap serial to GPIO15 and GPIO13.

So for flashing the sketch you connect your USB-TTL to ESP's TXD and RXD. After you call Serial.begin(), call Serial.swap(). UART will start talking on GPIO15(TXD) and GPIO13(RXD).