Power supply method: Use the USB power supply cable or external 5V power supply or downloader to power the core board through the JTAG port. All IO pins of the microcontroller are led to the two rows of pins of the core board and marked. +5V, 3.3V and GND are all led out with pins, which is convenient for users to do extended experiments. The frequency of the external crystal oscillator used on the board is 22.1184M. Users can use the internal crystal oscillator of the microcontroller or the external crystal oscillator. There are 3 buttons on the core board, one system reset button and two user buttons, and there are characters on the circuit board. Product name:C8051F330 core board PCB size: 6.7mmx4.6mm Serial port type: DB9 female socket External crystal oscillator: 22.1184M frequency User LED: 1 User buttons: 2 Colour:As Shown Material:plastic Package Contents: 1 * Development Board 1 * Cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.