There is a 16MB SPI Flash on the development board, and its location is shown in the figure below:

There is a tiny linux system programmed into SPI Flash by default, which is mainly used to prove that the development board can start normally. When you get the development board, you don't need to burn the system into the TF card, you only need to connect the Type-C power supply to the development board to start the micro linux system in the SPI Flash. The main functions of this system are: