( 配套程序2.2 )协议栈串口实验是调试时候常用的手段。源函数如下: uint16 HalUARTWrite(uint8 port, uint8 *buf,uint16 len) { (void)port; (void)buf; (void)len; #if(HAL_UART_DMA == 1) if (port == HAL_UART_PORT_0) return HalUARTWriteDMA(buf, len); #endif #if(HAL_UART_DMA == 2) if (port == HAL_UART_PORT_1) return HalUARTWriteDMA(buf, len); #endif #if(HAL_UART_ISR == 1) if (port == HAL_UART_PORT_0) return HalUARTWriteISR(buf, len); #endif #if(HAL_UART_ISR == 2) if (port == HAL_UART_PORT_1) return HalUARTWriteISR(buf, len); #endif #ifHAL_UART_USB HalUARTTx(buf, len); return len; #else return 0; #endif } 请调用上面的函数,使在串口0打印出“Hello World\n”字符: (10分)