How to flash Esp32-C3

[Enel96]

Hi there!! I am new working with ESP devices and I have a doubt about how ESP32-C3 is flashed. As far as I've seen in the datasheet, the device can be flashed over the UART0 using a USB/UART conversor. That is great because avoid the use of external programmers, that is always helpful. But, in the other hand, I've seen this board in aliexpress: https://a.aliexpress.com/_EwSKOx3
If you scroll down, you can see the schematics of this board and there I cant see any external USB to UART conversor in the pcb. I bought one of those and I can flash it directly over the usb-C connector... I see the USB is connected to GPIO20 and GPIO21. When I connect the device into the computer it detects a COM port and I can flash it over there, but without using UART0 interface but GPIO20 and GPIO21 instead. I'd like to know, if this is because those chips has an internal custom bootloader in order to allow usb flashing without the need of external components or all the Esp32-C3 come with that feature from factory? I am thinking in designing a pcb using this module and I'd like to know if I can use the same pinout for flashing that that board uses or, if I need to have at least UART0 available outside to flash the device, as well as boot and reset pins in order to put the device into flashing mode. What do you think? Now, the board I bought over aliexpress is not working anymore. When I connect the board to the computer it does not detect the COM port for flashing... should I be able to recover it if I use the external usb/uart and flash it using UART0 interface??

Thanks you for the help in advance!!!

Gretings

[ESP_Sprite]

The ESP32C3 (as well as some other ESP32 chips) have a built-in USB-serial-JTAG converter. The technical reference manual has the hardware details, but there's a nice summary in the esp-idf docs.