Sorry to reopen an old thread, but I stumbled into an issue after doing the modifications suggested by this post.
This work perfectly well for the USB connection, but I had to remove also two extra resistors (R21-R22) to disconnect the CP210 from U0TXD and U0RXD. Before doing that I was able to send ...

Ok, I found the issue.
We re-wired the ESP32C3 board to bypass the on-board USB2UART (we wanted to test in a situation close to the final HW setup).
We moved R1-R2 to R3-R4, as suggested here:
https://esp32.com/viewtopic.php?t=21007
But we didn't remove R21 and R22 so the UART pins were still ...

This thing is really driving me crazy.
I use the uart_echo example and I still can't receive any character on U0RXD/GPIO20.
I see output from ROM and the "hello" string, but sending character to that pin doesn't seem to lead to any result.
I also tried to use esp_rom to route that signal via GPIO ...

I did some more testing. I took the serial echo sample and leave log output only on USB Jtag/CDC.
I could run it using UART 1 controller on pins MTMS/GPIO4 for TX and MTDI/GPIO5 for RX.
I changed UART controller to UART 0 and it still works on the same pinout (so it doesn't seem to be an issue using ...

I need to use U0TXD and U0RXD as regular UART on ESP32-C3.
For testing, I am implementing a USB-to-UART bridge, from the physical UART to the USB-CDC one.
My test application is quite simple:


#include <stdio.h>

#include <driver/gpio.h>
#include <driver/uart.h>
#include <freertos/FreeRTOS.h ...

Thank you for the clarification, I contacted tech support.

I see this part number mentioned in the latest ESP32-C3 datasheet, but I couldn't find any description of the differences between this variant and those already available. I see from DS that SPI-flash pins are labeled as NC. From PN I suppose that flash size is 4MB, but I would like to know if there ...

As an alternative, is there a low-level documented APIs that allow me to perform the same operations done by that tool?
Continous TX etc.

Is it possible to run the tool using the integrate USB2CDC converter of the chip, without having to connect an external port?
I am testing with ESP32-C3-DevKitM-1 (rewired to route USB signals to the ESP, without using the on-board converter) and I can download the firmware, but get an access denied ...

Thanks a lot for the clarification.
Is this true for all the SPI interface signals, including WP, even if no external flash is connected?