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I used this wiring schematic for a couple of my ESP8266-12F projects for programming mode:

enter image description here

As I built enough confidence with the module, I decided to go ahead with a PCB design. When I try to upload a sketch, it wouldn't go into programming mode although I think my design is correct. I checked the connections between pads and headers and they all connected. Am I missing something here? Would you please check the connections and let me know of possible cause?

esptool.py v3.0
Serial port COM4'
Connecting........_____....._____....._____....._____....._____....._____...._____

esptool.FatalError: Failed to connect to ESP8266: Invalid head of packet (0xE0)

enter image description here

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  • \$\begingroup\$ I had a similar problem recently. It was due to not enough capacitance on the power supply. Fatten up your gnd and vcc tracks and add a 22uF 25V ceramic capacitor close to the module pads. Note that it is not a good idea to run tracks under the antenna or even the pcb. \$\endgroup\$
    – Kartman
    May 14 at 19:12

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Your top image shows TX to TX and RX to RX. Is that really correct or should it be TX to RX?

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  • \$\begingroup\$ I used the upper wiring tens of times. However, I swapped TX & RX but got the same issue. \$\endgroup\$ May 14 at 11:04
  • \$\begingroup\$ this answer should really be a comment \$\endgroup\$
    – jsotola
    May 14 at 18:34
  • \$\begingroup\$ Your enable pin is pulled low on one and high on the other. And, are you enabling GPIO-0 to the proper high/low to enable programming of the ESP12F? \$\endgroup\$ May 14 at 21:17

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