Feature: 1. GOOD PERFORMANCE: 40 Pin STM32F103C8T6 minimum system board module, with fine processing, has stable and reliable performance, less interference. 2. CIRCUIT DESIGN: Basic circuits based on microcontroller board, such as crystal oscillator circuit, USB interface and USB power management circuit, etc. 3. USB INTERFACE: Using the Mirco USB interface of the current smartphone, which is easy to use and can perform USB communication and power supply. 4. SWD INTERFACE: Use the SWD debugging interface to download, the interface needs at least 3 wires to complete the debugging of the download task. 5. 5PCS MODULES: Including 5pcs minimum system board modules, sufficient quantity, convenient for various DIY electrical testing, has strong practicability. Specification: Item Type: System Board Module Material: ABS Package List: 5 x Modules