Use this forum to chat about hardware specific topics for the ESP8266 (peripherals, memory, clocks, JTAG, programming)

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By btidey
#87899 It is true the D1 mini like other similar boards will upload / program automatically via the USB from a suitable IDE but this assumes that nothing extra is attached to the critical GPIO pins during this operation.

GPIO15 is pulled low on the board and GPIO0 and 2 are pulled high on the board. The upload sequence automatically pulls GPIO0 low to put it in serial flash mode. However, if any of these 3 pins is externally coonected to other logic signals that could disturb the process. It sounds like GPIO2 may have been pulled low by something external.
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By ClemensESP
#87909 Thanks for your answers.
My D1 was always unconnected (so only USB connected) when trying to flash (always with Arduino IDE)...
I also tried again after uploading an empty sketch...but same result, only works when pulling the right pins down/up.
No idea why it doesn't work automatically (after the very first flash which wrked automatically).

But it's ok now, I know how I can flash and it works reliable like this.