ESP-DOWD-V3 in custom PCB would not flash...

[Vilius]

Hi,

I a have a very typical problem, yet in not so typical circumstances...

I made a PCB that has an exact same replica of ESP32-WROOVER-E only embedded in the PCB directly rather than using off-the-shelf module. It took me a lot of time and effort examining the datasheets and reverse engineering the module, but I am confident that I did it right and saved some PCB space for my specific project. By saying that I did it right I mean the guarantee that everything you see in the provided schematic is indeed implemented in the PCB identically. However, I am not sure has the schematic been done correctly...

So my problem is that the MCU would not flash. For testing I wrote a very simple led blink project program using ESP-IDF. For flashing I use standard USB-RS232 (CP2102) converter. I have done a couple of projects (flashing standard ESP32 modules) using this method in the past, so I have no doubts that my hardware flashing setup works. PCB layout is not a consideration as well. I have fundamentals of it, so crystal is placed right next to the MCU, the PSRAM and FLASH are just couple of mm away from the MCU, sufficient decoupling, other than that there is nothing to be worried about. Components with designator J may look disturbing, but those are just testing point. Net labels BIT 1-12 are not connected anywhere, since I desoldered the shift registers that were connected to those.

My exact error: A fatal error occurred: Failed to connect to ESP32: No serial data received.

I am aware of the reset and boot button pressing sequence during the ,,Connecting........" phase. Like I said, I flashed some ESPs just like that in the past, so I understand the flashing procedure. I have already spent a lot of time trying to fix it, probing the circuit for voltages, shorts, checking the wiring etc. My hope is that I somehow misunderstood the ESP32 WROOVER datasheet and did some schematic mistake (check the attached datasheet that was my main guide while doing schematic). I highly appreciate any observations or hints. Thank you in advance

P.S. Tried to mention everything that looked relevant to me, however, if I missed something, please ask for clarification.

[ESP_Sprite]

Check the basics. Voltage rails OK? If you have a scope, can you see if the crystal oscillator is running? If you use a terminal on the serial port and reset the chip, do you get startup chatter?

[Vilius]

I have already done everything you mentioned. No problems in these steps.

[ESP_Sprite]

If you run a terminal and you start the chip with GPIO0 low, what message do you get?

[Vilius]

I can not even initialize the terminal communication. My terminal does not post any status flags about the chip.

[ESP_Sprite]

If you use a terminal on the serial port and reset the chip, do you get startup chatter?

I have already done everything you mentioned. No problems in these steps.

I can not even initialize the terminal communication. My terminal does not post any status flags about the chip.

So you didn't check if you saw startup chatter in the terminal? Did you not do any of the other steps I mentioned either?