ESP32-C3 USB/JTAG

[barryblake]

I'm designing my first ESP32 PCB and want to use a C3(-MINI). I'm a bit confused though looking at the C3 DevKit schematic, as it has a CH2102 USB-to-UART bridge: is that required or could I do without one?

If it's not required, why is it added? I can only think of the additional RTS/DTR pins so auto-reset works, or is there a way to do that as well with just the ESP32-C3-MINI?

[ESP_Sprite]

it is not required. Devkits tend to have one as initially we weren't sure if the USB-serial-JTAG device would work. Additionally, the USB-serial-JTAG device acts a little bit different than real USB-serial converters if you use light sleep (for now, it's an issue we're looking into) or deep sleep. If that is not a concern, there's absolutely nothing wrong with not adding a CP2102.

[axellin]

In my test, the "ESP RF test Tool" does not work if the USB-to-UART bridge is removed.

[barryblake]

it is not required. Devkits tend to have one as initially we weren't sure if the USB-serial-JTAG device would work. Additionally, the USB-serial-JTAG device acts a little bit different than real USB-serial converters if you use light sleep (for now, it's an issue we're looking into) or deep sleep. If that is not a concern, there's absolutely nothing wrong with not adding a CP2102.

Thanks for confirming, good to know. Is auto-flash/reset possible as well or would that then require a bridge with DTR/RTS connections?

[ESP_Sprite]

Yes, that is supported over the USB connection, no external wires needed. Note that during development you still may want to have some way to enter the bootloader (even if it's as simple as 'hotwiring' the ESP), as it's possible to 'break' the USB connection (e.g. by reconfiguring the USB pins as GPIO) and it's not possible to use USB to enter the bootloader anymore then.