ESP32 Forum

Hello,

We have a ESP32 WRover-B soldered on our PCB, and while trying to program it via Arduino IDE, it throws the error message " Failed to connect to ESP32: Timed out waiting for packet header".

So far, I have tried the following steps:

- Checked the power supply on EPS32 Vcc and GND. There is solid 3.3 Volts.

- Checked the CP2102N-A02-GQFN28 USB -UART Bridge, (when shorted at the Rx and Tx ) on the PCB, I can see that on my PC Terminal I get the typed characters back Echoed. Also as soon as I attach the USB my PC find the device and shows it in devmgmt.msc window.

- Check if the Tx - Rx of the CP2102N-A02-GQFN28 USB -UART Bridge are physically connected to ESP32 WRover-B Tx and Rx, the are.

- Check the Scope traces of the EN aka Reset GPIO and Boot Option aka GPIO-0. Please see the image below.

The schematics is attached as well, with the PCB layout data.







Please note! the swapped D+/D- on the USB entrance and on the ESP32 has been reworked and corrected. Also the (R52) track connecting to V3.3 ESP has been reworked and removed.

Currently I have added a 10mF Cap on Boot Option Switch to GND, and another 10mF cap on EN to GND.

The scope traces are after these changes.

Any information upon solving this hardware failure is highly appreciated.

David

If you use a terminal emulator (e.g. putty) on the serial port (@115200 n81) and reset the ESP32, do you receive anything? Normally you should get a sign-on message.

Also, I might be not be telling you anything new, but your circuit doesn't have an auto-reset circuit that can automatically put the ESP32 into bootloader mode. You need to do that manually: while holding the boot_opt button, press and release the reset button, then try flashing the chip.

currently when I am pushing and holding the EN Button, or Boot Option button, there is no message showing up in Terminal on my PC.
Just tried to program the ESP32 as you mentioned, pressing and holding Boot Option, then pressing the EN and then releasing the EN, then releasing the Boot Option, but it prints the same " Failed to connect to ESP32: Timed out waiting for packet header" error message inside Arduino IDE. Do you think there is an issue on hardware side? or software?

David

It's definitely a hardware issue, the error you're getting is basically what you get when the ESP32 is not responding at all; you'd also get it if you remove the ESP32 from the board entirely.

Looked over your schematic again, there's nothing there that's wrong. You may want to increase C80 to 1uF to get better power-on-reset behaviour, but that doesn't explain your current troubles. Perhaps you can try putting a scope to TXD0 of the ESP32, see if there's any activity at all there if you press and release the reset button? (Also, make sure GPIO15 is unconnected or high while doing that.)

okay guys, I found the issue. It was on this Silicon Labs CP xxxx USB-UART Bridge. The evil QFN package was faulty or badly soldered, there is a reason why I don't like them hehe.

Thanks a lot the input.

greetings from Physalis Labs Berlin ^_^