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

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By btidey
#75574 I know the pull up on RX is often recommended (and harmless), but I have never used it on many ESP-12Fs (no serial interface attached) and have never experienced any boot problems without it.

The RX pin has the internal pull up (~36k). Even if I deliberately pull this down with 2.2K, they still boot fine for me.
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By rudy
#75576 I tried it again last night. Ran a sketch, then disconnected the power, disconnected the serial connections, and it would not run the code. The module is a ESP-12E. I have not tried it with the ESP-12F.

I suspect that it is a software bug in the core routines (or bad decision) and hopefully corrected at some point. Maybe it has.
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By btidey
#75578 Interesting.

I have used 12Fs exclusively and I had thought the only significant difference was the aerial design but maybe they do tend to use an updated chip. I don't know if there is any calls one can use to get details on chip version.

Might be interesting to see if the module transmits anything out of TX with just the RX disconnected.