USB CDC on boot doesn't show up in my IDE

[Engineer-2D]

Board

ESP32 Dev Kit C V4 from AZ-Delivery

Device Description

ESP32 Dev Kit C V4 from AZ-Delivery

Hardware Configuration

There is no special configuration.
The board info is as follows:

BN: Unknown board
VID: 0x10C4
PID: 0xEAC0
SN: 0001

I chose ESP32 Dev Module

CPU frequency: "240 MHz (WiFi/BT)"
Core debug level: "None"
Events run on: "Core 1"
PSRAM: "Disabled"

Version

v3.3.3

Type

Task

IDE Name

Arduino IDE v2.3.6

Operating System

Windows 11

Flash frequency

80 MHz

PSRAM enabled

no

Upload speed

921600

Description

I have a code of sorts like this:

void setup() 
{
  pinMode(RFM95_RST, OUTPUT);
  digitalWrite(RFM95_RST, HIGH);

  Serial.begin(115200);
  delay(5000);
  while (!Serial) {};
  
  Serial.println("Arduino radio test!");
}

No matter how I change the conditions on Serial.begin, I cannot see the 'setup messages' in the Arduino IDE 2.3.6 Serial Monitor.
I modified some values in the boards.txt file.
C:\Users...\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.3.3, but nothing happened.
How can I view the messages during the setup process in my Serial Monitor?
On other ESP32 boards, such as the S3, this option is available to the user.
Sincerely,

Worried Engineer

Sketch

The sketch code is written above

Debug Message

No debug message because there is no compilation error

Other Steps to Reproduce

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[me-no-dev]

Everything looks OK in your setup. There is no reason on our end. It should have worked fine

[lbernstone]

Do you see the boot log if you reset the device, or nothing at all?
BTW, this is USB->UART, not USB-CDC.

[SuGlider]

Based on https://www.az-delivery.de/en/products/esp-32-dev-kit-c-v4
Win11 shall detect a CP210x USB to UART Bridge Virtual COM Port (VCP).
Please open your Windows Device Manager Application to check if the the ESP32 CP210x COM Port is listed.

Select the same COM port in Arduino IDE.
Open the Serial Monitor TAB, select 115200 baud and press the EN (reset) button.

It must display the BOOT UART Console log:

[Engineer-2D]

Response to @lbernstone: Thank you for your clarification regarding the USB-to-UART interface. I was indeed aware of this specification and posed the question primarily to contextualize this solution against alternative approaches available for comparable boards.
Response to @SuGlider: The following excerpt presents the output as it appears in the Serial Monitor console after pressing EN button which I already did yesterday to verify what happened:

09:23:14.230 -> ets Jul 29 2019 12:21:46
09:23:14.230 ->
09:23:14.230 -> rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
09:23:14.263 -> waiting for download

Response to @me-no-dev: The system should operate properly based on the configuration; however, it is currently not performing as expected.

[me-no-dev]

It looks like your board is entering download mode. Do you have something connected to it? If so, which IOs are you using? Anything on 0?

[Engineer-2D]

Response to @me-no-dev: You were absolutely right—GPIO 0 was connected as an interrupt request for another device. I'm puzzled by something in the manual: GPIO 0 is listed as supporting ADC 2-1, Touch 1, and RTC-11, yet switching the connection to GPIO 15 (which is ADC 2-3, Touch 3, and RTC-13 and SD CMD) resolved the issue. What are the key functional differences between these two pins?

[SuGlider]

09:23:14.230 -> ets Jul 29 2019 12:21:46
09:23:14.230 ->
09:23:14.230 -> rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
09:23:14.263 -> waiting for download

As @me-no-dev said, your board doens't boot in the normal mode in order to load and execute its firmware.

On the ESP32, the BOOT button is typically connected to GPIO0 and is used to put the chip into firmware flashing mode (serial bootloader mode).

How GPIO0 Works for Boot Mode

• Normal boot: GPIO0 is HIGH during reset/startup → ESP32 runs the program from flash.
• Flash/bootloader mode: GPIO0 is LOW during reset/startup → ESP32 enters UART download mode (used for uploading firmware via USB/serial).

On most dev boards:

• BOOT button → pulls GPIO0 to GND when pressed.
• EN/RESET button → resets the ESP32.

Manual flashing sequence (if auto-flash is not supported):

1- Hold BOOT.
2- Press and release RESET (EN).
3- Release BOOT after 1–2 seconds.
4- Upload firmware from the IDE.

Using GPIO0 as a Normal Input

You can use GPIO0 as a regular button input after boot, but:

Avoid pulling it LOW during reset unless you want to enter flash mode.
Use an internal pull-up to keep it HIGH when not pressed.
Be aware that some boards have it hardwired to the BOOT button.

[SuGlider]

Response to @me-no-dev: You were absolutely right—GPIO 0 was connected as an interrupt request for another device. I'm puzzled by something in the manual: GPIO 0 is listed as supporting ADC 2-1, Touch 1, and RTC-11, yet switching the connection to GPIO 15 (which is ADC 2-3, Touch 3, and RTC-13 and SD CMD) resolved the issue. What are the key functional differences between these two pins?

GPIO0 is a regular GPIO as the manual says, but it can't be held LOW when the board resets.
ROM code will detect it and put the ESP32 in download mode automatically.
After RESET, the firmware can use that GPIO for anything.