ESP32-C3 super mini boot log thru the USB port

1

Does someone have a trick on how to see the boot log on an ESP32-C3 super mini? I mean every time you reboot the PIO monitor gets disconnected (the USB device is removed) and before you are ready to connect again the boot log is long gone. I even had to put in a 10 sec. delay at the beginning of the application in order to get the App. log.

2

This is due to the fact that this board uses the native USB port of the ESP32-C3. As this is integrated in the MCU, it is also restarted on a reboot and loses the connection to the PC.

The extension Serial Monitor is available for VS Code.
This allows an automatic reconnection if the connection is lost:

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image825×250 14.8 KB

3

Thanks for the reply!
Yes I also concluded that it was the USB port being disconnected, but I couldn’t find what to do about it. I will try the ‘Serial Monitor’ extension - thanks for the hint. :+1:

4

@sivar2311 I tried the ‘Serial Monitor’ extension, but I am still missing the boot log I only see the App. log. Maybe the ESP32-C3 don’t output a boot log as e.g. the ESP32-WROOM?
BTW do you know if the ‘Serial Monitor’ takes the ‘monitor_filters = esp32_exception_decoder’ from the platformio.ini into account?

5

It does:

ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x15 (USB_UART_CHIP_RESET),boot:0xf (SPI_FAST_FLASH_BOOT)
Saved PC:0x400462e2
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd5820,len:0x1144
load:0x403cc710,len:0xad8
load:0x403ce710,len:0x2f80
entry 0x403cc710

Using the Serial Monitor plugin you can use the DTR / RTS to force an USB_UART_CHIP_RESET

Open the Serial Monitor plugin and click on the tooth gear icon.
This brings up an additional line:

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Check / Uncheck the DTR / RTS in the following sequence:

DTR
RTS
DTR

The ESP32-C3 is now in the download mode and should show:

ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x15 (USB_UART_CHIP_RESET),boot:0x7 (DOWNLOAD(USB/UART0/1))
Saved PC:0x40383006
waiting for download

Continue the sequence:
RTS
RTS
This reboots the ESP32-C3 in normal mode. Now you should see the complete boot log:

ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x15 (USB_UART_CHIP_RESET),boot:0xf (SPI_FAST_FLASH_BOOT)
Saved PC:0x40046c9e
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd5820,len:0x1144
load:0x403cc710,len:0xad8
load:0x403ce710,len:0x2f80
entry 0x403cc710
6

@sivar2311 Wow, that is very nice - the solution to my question, thanks.
Wonder why this reset dosn’t disconnect the USB port. I guess that this emulated USB port doesn’t use the HW flow control for a hard reset as done on the ESP32devkit USB chip.

I rest my case. :grinning: :+1: