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I designed a PCB based on an MPU9250 IMU, an ESP8266-12F, and an FT232RL UART-TTL bridge. You can see schematics for the USB to UART, and ESP8266 circuits here.

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When I researched about the UART part of the circuitry, I saw numerous exampled mentioning FTDI USB modules and ESP8266 bare chip programming. Therefore, I built my USB-UART circuit based on an FTDI module and used thr FT232RL.

I am not able to program using the Arduino IDE NodeMCU flashing configurations. When I press the reset button while holding the GPIO0 button I see the following from the serial port. I thought the ESP goes to boot mode, I am not able to communicate or upload the code.

What should I do in order to communicate with the ESP and upload firmware? I know I may not have provided enough information. I am willing to share more if you ask.

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This is what I get when I upload the code. It says "chosen serial port can not be found in attached board" and timed out when waiting for packet header:

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The problem is pin11 GPIO2 of the ESP12F. It must pulled up to 3.3V for each operation mode of the ESP. The datasheet of the ESP12F states that GPIO2 is also I2C_SDA pin. Does it makes sense for a pin that needs to pulled up during operation to be SDA at the same time?

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Here is a state configurations for normal operation mode and flashing mode:

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  • \$\begingroup\$ So it seems that the ESP can send data to PC, but the PC may not be able to send to ESP? If so, have you checked that wiring and soldering, so that there is no problems between FTDI TXD output and ESP RXD input? \$\endgroup\$
    – Justme
    Oct 16, 2020 at 18:19
  • \$\begingroup\$ "It says "chosen serial port can not be found in attached board" that suggests you've picked the wrong serial port during the programming (vs serial monitor) attempt. Your FTDI picture is nearly too small to read, but your power supply to the chip is coming from a mysterious unidentified source rather than the USB connector where it probably should be. Perhaps your FTDI device is not active when you are trying to do this.. \$\endgroup\$
    – Chris Stratton
    Oct 16, 2020 at 18:24
  • \$\begingroup\$ Please post a real and complete schematic large enough to be legible not these tiny incomplete portions which leave too much critical connectivity missing. \$\endgroup\$
    – Chris Stratton
    Oct 16, 2020 at 18:25
  • \$\begingroup\$ thanks for your comments I am posting whole schematic clearly. \$\endgroup\$
    – tronics
    Oct 16, 2020 at 18:26

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