From 893bb729071c8af9bfba2df5c7c1daed57afa448 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=91=A8=E4=BC=A0=E7=A6=8F?=
 <46174387+zhouchuanfu@users.noreply.github.com>
Date: Mon, 20 May 2019 10:21:00 +0800
Subject: [PATCH] Update drv_usart.c

---
 bsp/stm32/libraries/HAL_Drivers/drv_usart.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/bsp/stm32/libraries/HAL_Drivers/drv_usart.c b/bsp/stm32/libraries/HAL_Drivers/drv_usart.c
index 2950266b3c..039d008341 100644
--- a/bsp/stm32/libraries/HAL_Drivers/drv_usart.c
+++ b/bsp/stm32/libraries/HAL_Drivers/drv_usart.c
@@ -634,11 +634,13 @@ void LPUART1_DMA_RX_IRQHandler(void)
 #ifdef RT_SERIAL_USING_DMA
 static void stm32_dma_config(struct rt_serial_device *serial, rt_ubase_t flag)
 {
-    RT_ASSERT(serial != RT_NULL);
     struct rt_serial_rx_fifo *rx_fifo
     DMA_HandleTypeDef *DMA_Handle;
     struct dma_config *dma_config;
-    struct stm32_uart *uart = (struct stm32_uart *)serial->parent.user_data;
+    struct stm32_uart *uart;
+    
+    RT_ASSERT(serial != RT_NULL);
+    uart = (struct stm32_uart *)serial->parent.user_data;
     RT_ASSERT(uart != RT_NULL);
 
     if (RT_DEVICE_FLAG_DMA_RX == flag)