How to set a NUCLEO G474RE into DFU(Device Firmware Update) mode ?

[MQi.1]

I mean, is there any button or pins I could press when power on then make it into DFU mode, and the DFU mode would be recognized by Ubuntu?

[TDK]

Not easily.

This board only has a single USB connector (CN1) which is connected to the ST-Link chip, not the STM32G474. So that won't help you.

You would need to solder a USB connector to the relevant pins, then put the device in bootloader mode by holding BOOT0 high during reset. Then it would be recognized as a DFU.

[MQi.1]

So I need 3 components - USB socket, USB-TTL convertor, and 5v to 3.3v regulator?

[TDK]

Just a USB socket. There are 5V pins on there which can be used to supply power from an external source (VBUS). See user manual for details about the power options. Not sure why you'd need a USB-TTL converter.

[MQi.1]

I have thought I need to program the chip by UART as an AVR.