ESP32 Forum

Hi,

I am new to this forum so sorry if this topic already exists.
I am developing a PCB with some sensors and I bought a ESP-WROOM-32 to use to send data to my server. The ESP32 is soldered onto the PCB and all connections are correct but I am not able to flash it. I am using the transistor circuit of one of the ESP32-kits (same used by Sparkfun also) which is connected to the DTR and RTS signals of the USB/UART bridge which resets the ESP32 and makes it launch the flashing mode of the bootloader. The thing is that I get a time-out when trying to flash it since it doesn't respond. I went through the start guide on how to compile and flash a ESP32 module but that it is not working. I checked my hardware design and everything seems correct so I started thinking that maybe the ESP32 doesn't come with a loaded bootloader and therefore it needs to be programmed first in order to upload your code through the bootloader. I am not sure about it because I tried to find some documentation on how to program the device (by using JTAG for example) and struggle.

Does anyone have the same problem or has faced this problem?

Thank you in advanced!

Not sure what's wrong in your specific case, but the ESP32 comes with the bootloader in it's (non-writable) ROM, so you should always be able to upload new software, no initial flashing required.

Hi daniel.kjellstrom,

Does the ESP-WROOM-32 module respond correctly in the simplest configuration, without "using the transistor circuit"?

1. Do you see some log output by the module as described in Verify serial connection?

2. If yes, then what log do you see if you reset the module while holding GPIO0 low? This puts the module into upload mode and you should see a specific response on the terminal.

Hi,

@ESP_Sprite
Thank you for the information. Glad to hear that it already has a bootloader.

@krzychb
I didn't check the "verify serial connection" site, I will do check it out. Also I will try to enter the bootloader manually without the "transistor's circuit". Thank you for your reply

Hi again,

Found the problem. It was my ftdi USB/UART bridge which wasn't very good soldered. I checked the "Establish Serial Connection" page and connect the ESP32 to my computer. I get data but with weird characters. I could distinguished a "June" word but nothing else. Here comes a screenshot. I checked the serial monitor settings and everything is alright. Even tried with different baud rates but got nothing.