add support for GD32F310G-START

board/GD32F310G_START/BSP/Src/usart.c

@@ -0,0 +1,43 @@
+/**
+  ******************************************************************************
+  * File Name          : USART.c
+  * Description        : This file provides code for the configuration
+  *                      of the USART instances.
+  ******************************************************************************
+  * @attention
+  *
+  * <h2><center>&copy; Copyright (c) 2019 STMicroelectronics.
+  * All rights reserved.</center></h2>
+  *
+  * This software component is licensed by ST under BSD 3-Clause license,
+  * the "License"; You may not use this file except in compliance with the
+  * License. You may obtain a copy of the License at:
+  *                        opensource.org/licenses/BSD-3-Clause
+  *
+  ******************************************************************************
+  */
+
+/* Includes ------------------------------------------------------------------*/
+#include "usart.h"
+
+/**
+  * @brief 板级 usart 硬件初始化
+  * @param void:
+  * retval N/A.
+  */
+int board_usart_init(void)
+{
+    rcu_periph_clock_enable(RCU_USART0);
+    usart_deinit(RCU_USART0);
+    usart_baudrate_set(USART0, 115200);
+    usart_stop_bit_set(USART0, USART_STB_1BIT);
+    usart_word_length_set(USART0, USART_WL_8BIT);
+    usart_parity_config(USART0, USART_PM_NONE);
+    usart_transmit_config(USART0, USART_TRANSMIT_ENABLE);
+    usart_receive_config(USART0, USART_RECEIVE_ENABLE);
+    usart_interrupt_enable(USART0, USART_INT_RBNE);
+    usart_enable(USART0);
+    nvic_irq_enable(USART0_IRQn, 0, 0);
+
+    return 0;
+}