ESP32 Forum

Hi, I might screw something up.
In the afternoon, is forgot to disconnect battery from my protoboard project, and I connected my ESP to my computer via USB. I didn't do anything (didn't had time) it was just connected few hours with usb and battery to dedicated battery connector on dev board. But few hours ago I tried to program it and I got an error I tried all the google solutions, PRG button holding before/during upload, same with RST, tried combination of holding it pressed or not at same time, release RST before PRG etc, etc,... I tried pulling down/up gpio, nothing, always same mistake. I tried connecting it with ESP tools, and deleting flash. Did I burn something because when I somehow bricked other esp board, I salvaged it with esptool and its working normally now, but this one is giving me headache . It seems like RST button doesn't actually reset. Just red led blinking all the time, and no serial output or anything

I also experienced exact same error on one of the ESP 32 board.

Serial port COM3
Connecting........_____....._____....._____....._____....._____....._____.....____An error occurred while loading the sketch.
_
A fatal error occurred: Failed to connect to ESP32: Invalid head of packet (0x00)

I could upload program to another board but was failing with one specific board.
1. I tried reducing "Flash Frequency" from Tools-->Flash Frequency from 80Mhz to 40Mhz
2. Tried reducing the "Upload speed" Tools-->Upload speed
3. Changing different board types
4. Holding "Boot" button till process completes
5. Tried different combination of Boot and En button Press and release

Finally I inspected ESP32 chip to PCB connectivity and found that 3.3v supply pin of ESP32 was not [properly soldered to PCB and was causing g the issue. Once it was soldered, everything worked fine