Mbed NUCLEO L432KC 结构 PIN图 ST-Link COM LED 状态 特点 ARM®32-bit Cortex®-M4 CPU 80 MHz max CPU frequency 256 KB Flash 64 KB SRAM GPIO (20) with external interrupt capability 12-bit ADC with 12 channels Timers (4) I2C (2) USART (2) SPI (2)