Can I still flash wemos/lolin ESP32 via pin headers if USB is destroyed?

Projects Programming
1

I have now 5 of those that got their USB damaged in a way that it will power from USB, but the usb-serial chip is dead, so I can't flash them the normal way anymore. This happened when I plugged them into some board that does something I haven't figured out yet, but indeed seems to destroy the USB chip somehow.

They otherwise work fine, I can get output on the serial pins via an ftdi serial adapter, and I can also send input, my code receives it and it works.
So I should still be able to flash them via those serial pins, no?
I do see the normal messages from the ESP32 bootloader on serial but when running the arduino flasher, I get

Connecting........_____....._____....._____....._____....._____....._____....._____....._____....._____....._____
A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header

I tried to push the reset button during this time, and it didn't help.
I also tried to short GPIO0 to GND or connect it via a 10k resistor before or after pushing the reset button and during this time arduino is trying to connect, but again, no luck.

Is there still a way I can flash them?

2

If the burned USB chip is not tie down or tie up the serial pins of the ESP32, you may be able to program them using a USB/TTL module.
You may remove your bad interface too.
I use it here on my ESP32 standalones.

Put yellow jumper in 3.3V.

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3

I used one of those (mentioned ftdi usb serial adapter).
The one thing I may not have done right is that I was powering the chip via USB. I could try to power it directly without powering the damaged USB chip at all.

4

i'm not sure why it wasn't working when I first tried, but it is working now after pulling GPIO to GND while pushing RST to enable flash mode
rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download

5

Now that i've figured out how to flash around a broken USB chip I need to figure out why I'm burning those chips.

I'm not connected the USB header to anything other than my laptop, and I do power the chip from an external 5V source directly on its USB pin, and it should be about 5V. Is there a way to fry the USB chip without frying the ESP32 voltage regulator?

6

This was the schematic of your wemos/lolin ESP32 that I found on the web.
See how the regulator is connected.

Ref: D32 — WEMOS documentation

and

7

Sure, not surprisingly the USB chip is connected directly to the 5V rail and not protected by the voltage regulator.
I suppose that means my circuit could send more than 5V, but I'm not sure it does, or something like 5.1 or at most 5.2V, I'd have to go measure it.

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