ESP32: Issue with receiving of Serial Data

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1

Hi guys,
I´m currently working on a school project where I want to receive a cars CAN-Bus data via the OBDII-port using a Bluetooth adapter and a ESP-WROOM-32E. I´m obviously using PIO with VS-Code which worked great on a ESP32 Development Board. But I have decided to make my own custom PCB. After soldering everything together and checking the connections and stuff I decided to test the circuit board uploading a short sketch. Unfortunately the message: “A fatal error occurred: Failed to connect to ESP32: No serial data received.” popped up. I did some research and found that it might have to do with the bootloader which isn´t being selected right. Is there anything I can do to solve this problem? I tried to manually get it into the right bootloader mode by connecting GPIO0 to GND with a jumper wire and then tapping the EN-Pin onto GND but It didnt help. Do you guys have any Idea what I could do?

Kind regards,
Michael

P.s. Here are some screenshots of the schematics if they help in any way:
https://drive.google.com/drive/folders/1XY2tsWJTWB-_UTFmTjjDCu0JIRSd_67n?usp=drive_link

2

Unfortunately it is not just GPIO0.
There are also the GPIO’s 2, 12 and 15 involved:

GPIO2 must also be either left unconnected/floating, or driven Low, in order to enter the serial bootloader. In your schematics there is TFT_RS conneced to GPIO2.

https://docs.espressif.com/projects/esptool/en/latest/esp32/advanced-topics/boot-mode-selection.html

3

Thanks for the answer. I tried it with GPIO0 driven low but unfortunately it didnt help. I followed this:

  • GPIO 0 (must be LOW to enter boot mode)
  • GPIO 2 (must be floating or LOW during boot)
  • GPIO 4
  • GPIO 5 (must be HIGH during boot)
  • GPIO 12 (must be LOW during boot)
  • GPIO 15 (must be HIGH during boot)

But the error still persists

4

What about GPIO2? What level does it have when booting?

In your schematic it is connected to TFT_RS, but it should be floating or better pulled LOW at boot)

5

GPIO2 is on LOW while booting… I´m currently not using it, but I´m gonna use it later on for a tft display