Usage Tips:Item Type: Microcontroller System Board Material: PCB Board Size: Approx. 12 x 18mm / 0.47 x 0.71in 1,Better Control: One on board MCU controls LED, and the IO port can connect to P3.2 for output, such as PWM wave modulation experiment. 2,One Way Switch: One channel switch chip on board, connect to IO port P3.3, which can be used for input, interrupt and other experiments. 3,Stable Working: The switches and LEDs of the external chips of the IO port do not affect the normal use of the IO port. 4,4 Sets in All: There are 4 sets of MCU development board, and the large quantity will meet your needs for replacement. 5,All IO Port Out: All IO ports are led out, so the light weight and compact microcontroller system board is easy to install.4 x Microcontroller System Board 4 x Pin Header Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.