1、功能说明

    该测例演示了USARTy与USARTz间通过DMA（查询）实现的基础通信。USARTy和
USARTz可以是USART1和USART2。
    首先，DMA传输TxBuffer1数据至USARTy发送数据寄存器，随后数据发送至
USARTz。USARTz接收数据，DMA从USARTz接收数据寄存器搬移数据至RxBuffer2。
比较收、发数据，比较结果存入TransferStatus2变量。
    同时，DMA传输TxBuffer2数据至USARTz发送数据寄存器，随后数据发送至
USARTy。USARTy接收数据，DMA从LPUART接收数据寄存器搬移数据至RxBuffer1。
比较收、发数据，比较结果存入TransferStatus1变量。   


2、使用环境

    软件开发环境：EIL MDK-ARM V5.34.0.0
                  IAR EWARM 8.50.1
    硬件环境：N32G401C8L7-STB V1.0


3、使用说明

    系统时钟配置如下：
    - 时钟源 = HSE + PLL
    - 系统时钟 = 72MHz
    
    USART配置如下：
    - 波特率 = 115200 baud
    - 字长 = 8数据位
    - 1停止位
    - 校验控制禁用
    - 硬件流控制禁用（RTS和CTS信号）
    - 接收器和发送器使能
    - DMA发送模式和DMA接收模式使能
    
    USART引脚连接如下：
    - USART1_Tx.PA9    <------->   USART2_Rx.PA3
    - USART1_Rx.PA10   <------->   USART2_Tx.PA2

    
    测试步骤与现象：
    - Demo在KEIL环境下编译后，下载至MCU
    - 复位运行，依次查看变量TransferStatus1和TransferStatus2，其中，
      PASSED为测试通过，FAILED为测试异常


4、注意事项

    需先将开发板NS-LINK的MCU_TX和MCU_RX跳线帽断开



1. Function description

     This test example demonstrates basic communication between USARTy and USARTz through DMA. USARTy and USARTz
     can be USART1 and USART2. 
     First, the DMA transfers the TxBuffer1 data to the USARTy transmit data register, and then the data is sent to the 
     USARTz. USARTz uses the interrupt to receive data and store it in RxBuffer2. 
     At the same time, the DMA transfers the TxBuffer2 data to the USARTz transmit data register, and then the data is 
     sent to the USARTy. USARTy receives data by querying the check flag and stores it in RxBuffer1. 
     Finally, the two groups of receiving and sending data are compared respectively, and the comparison results are 
     stored in the TransferStatus1 variable and the TransferStatus2 variable. 


2. Use environment
    Software development environment: KEIL MDK-ARM V5.34.0.0
                                      IAR EWARM 8.50.1
    Hardware environment: Developed based on the evaluation board N32G401C8L7-STB V1.0



3. Instructions for use
     The system clock configuration is as follows:
     - Clock Source = HSE + PLL
     - System Clock = 72MHz
    
     USART is configured as follows:
     - Baud rate = 115200 baud
     - Word length = 8 data bits
     - 1 stop bit
     - checksum control disabled
     - Hardware flow control disabled (RTS and CTS signals)
     - Receiver and transmitter enable
     - DMA transmit mode enabled, DMA receive mode disabled
    
     The USART pins are connected as follows:
     - USART1_Tx.PA9 <-------> USART2_Rx.PA3
     - USART1_Rx.PA10 <-------> USART2_Tx.PA2

    
     Test steps and phenomena:
     - Demo is compiled in KEIL environment and downloaded to MCU
     - Reset operation, check the variables TransferStatus1 and TransferStatus2 in turn, where,
       PASSED is the test passed, FAILED is the test abnormal


4. Attention
    the MCU_TX and MCU_RX jumper cap of the development board NS-LINK needs to be disconnected first