Two transistor reset circuit with a disconnected UART.

[gantzm]

When using the two transistor reset circuit can the DTR and RTS signals be left to float or should they be pulled up or down? The situation is a board that includes the micro controller and the reset circuit, but the UART (CP2102N in this case) is off board and not always connected.

What is best practice for these pins? I'm guessing I might want to pull DTR and RTS low with 10K resistors. But that is purely a guess.

Any assistance would be greatly appreciated.

[Geir_Moen]

Without knowing what kind of USB-to-Serial you use, I cannot tell you if you need pull-down resistors for the transistors.
That said, pull-down resistors should not hurt.
In my case, I used another ESP32 to control the transistors that controlled "EN" and "BOOT" on a target ESP32.
In my project, I needed pull-up resistors on the target "EN" and "BOOT" pins. I used 10k ohm resistors.
The target ESP32 were held in a continuous reset because the "EN" pin were never lifted to 3.3 volt.
I should also mention that my "target" ESP32 was a clean ESP32-WROOM32. No developing board.

Hope this helps.
Kind regards,
Geir Moen