ESP32 Forum

Hi,

If I use the esptool to access something on my ESP32 device (like "esptool flash_id"), it fail and says it cannot connect because the device cannot be switched to bootloader mode. A few times it worked, but most of the time it fails with this error:


This happens only for auto connect. If I manually press the BOOT button while connecting, it succeeds every time !

My setup is: a laptop with Windows 10, and a ESP32-DevKitC-VE with WROVER-E N8R8. The board was purchased from the official Espressif store on Aliexpress and it has auto-upload capabilities (using DTR/RTS). I installed the official CP210x_Universal_Windows_Driver and the board is successfully detected on COM3. Then I installed Arduino IDE and VSCode with the Platform IO extension. Nothing works...

Does it work when you switch into download mode manually? (Hold boot button, press and release reset button)

Yes ! It works every time, with any version, if I press and hold the BOOT button while esptool tries to connect.

Could be a timing issue. A hack that usually works is to add a capacitor (try 1 to 10uF) between EN and GND.

I've done some testing...

I usesd in esptool.cfg "custom_reset_sequence = D1|W3|D0|W3". Just to see if the signals are present and they have correct polarity.
When I executed "esptool flash_id", the level at IO0 (boot) pin indeed goes from HIGH to LOW and back, while the EN pin stays HIGH.

Then I checked the other line with "custom_reset_sequence = R1|W3|R0|W3".
When I executed "esptool flash_id", the voltage level at EN pin indeed goes from HIGH to LOW and back, but ! the IO0 (boot) pin goes too from HIGH (3.3V) to some LOW level of 0.2V ! Maybe because the chip is in reset state and the voltage is not present ?

Is this normal so far ?

I will try with the capacitor on EN pin too, but lets see if I can, because everyting on that board is so small...

Edit:
It seems that when esptool toggle the RTS line the DTR output pin of CP2102N drops to 0.65V. I don't understand why DTR is changed if I only toggled the RTS from software...

I added 1uF capacitor between the EN pin and ground and now it works perfectly ! Thanks !
Why do yo not include it on the board ?