1、功能说明
    本工程为有操作系统（FreeRTOS）的DNS示例。通过DNS解析域名。

2、使用环境

    软件环境：
        KEIL MDK-ARM 5.34.0
        IAR EWARM 8.50.1
    
    芯片支持：
        N32H730  
        N32H735   
        N32H735EC
        N32H760
        N32H762
        N32H765
        N32H765EC
        N32H785
        N32H785EC
        N32H787

3、使用说明
    
    系统配置：
        1、时钟源：HSI+PLL
        2、时钟频率：M7：600MHz，M4：300MHz
        3、打印：PA9 - baud rate 115200

    以太网配置：
        1、PHY接口：GMII
        2、引脚分配：
            ETH1_MDC <-----> PC1
            ETH1_MDIO <-----> PA2
            ETH1_GMII_RXDV <-----> PA7
            ETH1_GMII_TXD0 <-----> PG13
            ETH1_GMII_TXD1 <-----> PG12
            ETH1_GMII_TXD2 <-----> PE3
            ETH1_GMII_TXD3 <-----> PE2
            ETH1_GMII_TXD4 <-----> PI4
            ETH1_GMII_TXD5 <-----> PI5
            ETH1_GMII_TXD6 <-----> PI6
            ETH1_GMII_TXD7 <-----> PI7
            ETH1_GMII_TXEN <-----> PG11
            ETH1_GMII_RXD0 <-----> PC4
            ETH1_GMII_RXD1 <-----> PC5
            ETH1_GMII_RXD2 <-----> PH6
            ETH1_GMII_RXD3 <-----> PH7
            ETH1_GMII_RXD4 <-----> PE12
            ETH1_GMII_RXD5 <-----> PE13
            ETH1_GMII_RXD6 <-----> PE14
            ETH1_GMII_RXD7 <-----> PE15
            ETH1_GMII_RXCLK <-----> PA1
            ETH1_GMII_COL <-----> PH3
            ETH1_GMII_CRS <-----> PA0
            ETH1_GMII_RXER <-----> PB10
            ETH1_GMII_TXER <-----> PB2
            ETH1_GMII_TXCLK <-----> PC3
            ETH1_GMII_GTXCLK <-----> PF5
            ETH1_CLK125 <-----> PD10

    使用方法：
        1、电脑和开发板均用网线连接路由
        2、修改HOST_NAME，设置要解析的主机名，修改USE_BLOCKING，设置调用阻塞式API或非阻塞式API
        3、编译后下载程序运行，串口将打印解析的IP地址等信息
        4、用户可以在电脑端ping主机名，检查回复信息中IP地址是否与打印的IP地址相同

4、注意事项
    1、您使用的PHY芯片可能与demo默认选择的不一样，请在bsp_eth.h中切换或添加其他PHY的定义；请注意PHY_ADDR，PHY地址值必须与硬件设计保持一致
    2、需要使用DNS功能时，注意设置DNS服务器地址，本例程在lwipopts.h中定义了DNS_SERVER_ADDRESS，并将8.8.8.8（谷歌）设置为DNS服务器地址，用户可根据需要修改该地址；如果同时使用了DHCP功能，该DNS服务器地址也可以设置为由DHCP获取的网关地址（gw）
    3、如果不使用DHCP功能，则必须确保开发板的静态IP地址与路由器处于同一网段（开发板静态IP默认为：192.168.0.32），并与该局域网内的其他设备无IP地址冲突
    4、建议在使用DNS功能时，同时也开启DHCP功能


1. Function description
    This project is an example of DNS with an OS (FreeRTOS). Resolve domain names via DNS.

2. Development environment

    Software environment:
        KEIL MDK-ARM 5.34.0
        IAR EWARM 8.50.1
    
    Supported chips:
        N32H730  
        N32H735   
        N32H735EC
        N32H760
        N32H762
        N32H765
        N32H765EC
        N32H785
        N32H785EC
        N32H787

3. How to use
    
    System configuration:
        1, clock source: HSI + PLL
        2, clock frequency: M7: 600MHz, M4: 300MHz
        3, print: PA9 - baud rate 115200

    Ethernet configuration:
        1, PHY interface: GMII
        2, Pin assignment:
            ETH1_MDC <-----> PC1
            ETH1_MDIO <-----> PA2
            ETH1_GMII_RXDV <-----> PA7
            ETH1_GMII_TXD0 <-----> PG13
            ETH1_GMII_TXD1 <-----> PG12
            ETH1_GMII_TXD2 <-----> PE3
            ETH1_GMII_TXD3 <-----> PE2
            ETH1_GMII_TXD4 <-----> PI4
            ETH1_GMII_TXD5 <-----> PI5
            ETH1_GMII_TXD6 <-----> PI6
            ETH1_GMII_TXD7 <-----> PI7
            ETH1_GMII_TXEN <-----> PG11
            ETH1_GMII_RXD0 <-----> PC4
            ETH1_GMII_RXD1 <-----> PC5
            ETH1_GMII_RXD2 <-----> PH6
            ETH1_GMII_RXD3 <-----> PH7
            ETH1_GMII_RXD4 <-----> PE12
            ETH1_GMII_RXD5 <-----> PE13
            ETH1_GMII_RXD6 <-----> PE14
            ETH1_GMII_RXD7 <-----> PE15
            ETH1_GMII_RXCLK <-----> PA1
            ETH1_GMII_COL <-----> PH3
            ETH1_GMII_CRS <-----> PA0
            ETH1_GMII_RXER <-----> PB10
            ETH1_GMII_TXER <-----> PB2
            ETH1_GMII_TXCLK <-----> PC3
            ETH1_GMII_GTXCLK <-----> PF5
            ETH1_CLK125 <-----> PD10

    Usage:
        1, Computer and development board are connected to the route with a network cable.
        2, Modify HOST_NAME to set the hostname to be resolved, and modify USE_BLOCKING to set whether to call the blocking API or the non-blocking API.
        3, Compile and download the program to run, the serial port will print the resolved IP address and other information.
        4, Users can ping the hostname on the computer side to check if the IP address in the reply message is the same as the printed IP address.

4. Attention
    1, The PHY chip you are using may differ from the default selection in this demo. Please switch or add definitions for other PHYs in bsp_eth.h. Note that the PHY_ADDR value must match the hardware design.
    2, When you need to use the DNS function, pay attention to set the DNS server address. This routine defines DNS_SERVER_ADDRESS in lwipopts.h and sets 8.8.8.8 (Google) as the DNS server address, which can be modified by the user according to the need; If the DHCP function is also used, this DNS server address can also be set to the gateway address (gw) obtained by DHCP.
    3, If you do not use the DHCP function, you must ensure that the static IP address of the board is in the same network segment as the router (the default static IP address of the board is 192.168.0.32) and that there is no IP address conflict with other devices on the LAN.
    4, It is recommended that you use the DNS function while also enabling the DHCP function.

