1. 准备工作

LwIP正式移植之前，登录LwIP官方网站：https://savannah.nongnu.org/projects/lwip/，此网站包含有关LwIP协议的各种信息，可根据兴趣进行查看。若要下载源码，点击进入到LwIP协议的源码下载界面。这里您可以看到LwIP协议各个版本的发布包，根据需求选择适当版本的“contrib”和“lwip”源码包进行下载，下载完成后解压便可看到LwIP的所有源码。本文中选取的LwIP源码包的版本分别是“contrib-2.0.1”和“lwip-2.0.3”。

2. 裸机移植LwIP

2.1 LwIP目录创建

裸机移植LwIP主要应用到“lwip-2.0.3src”目录下的源码文件夹（api、core、和netif）和头文件夹（include），移植时可在自己的工程中创建“LwIP”目录，并在此目录下分别建立api、core、netif和include目录，如下图所示：

2.2 LwIP源文件移植

接下来需要往工程的各个目录中添加LwIP源文件（以IPV4版本协议的移植为例）：
工程api目录：添加“lwip-2.0.3srcapi”中的所有文件；

工程core目录：添加“lwip-2.0.3srccore”中除“ipv6”外的所有文件和目录；

工程netif目录：添加“lwip-2.0.3srcnetif”中的所有文件：

至此，裸机移植LwIP所需的所有源文件都已添加完成，接下来是往工程中添加头文件。

2.3 LwIP头文件移植

工程include目录：添加“lwip-2.0.3srcinclude”中的所有文件：

在工程中“LwIP”目录下创建“port”目录，并在工程“port”目录下创建“includearch”目录。将“contrib-2.0.1portsunixminimal”目录下的“lwipopts.h”文件添加至工程“portinclude”目录中，将“contrib-2.0.1portsunixportincludearch”目录下“cc.h”和“perf.h”文件添加至工程目录“portincludearch”下，添加完成后如下图所示：

lwipopts.h是对LwIP协议使用功能的配置文件，类似于FreeRTOS系统文件中的FreeRTOSConfig.h文件。一个配置例程如下所示：

/**  * @file  *  * lwIP Options Configuration  */  /*  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.  * All rights reserved.   *   * Redistribution and use in source and binary forms, with or without modification,   * are permitted provided that the following conditions are met:  *  * 1. Redistributions of source code must retain the above copyright notice,  *    this list of conditions and the following disclaimer.  * 2. Redistributions in binary form must reproduce the above copyright notice,  *    this list of conditions and the following disclaimer in the documentation  *    and/or other materials provided with the distribution.  * 3. The name of the author may not be used to endorse or promote products  *    derived from this software without specific prior written permission.   *  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT   * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY   * OF SUCH DAMAGE.  *  * This file is part of the lwIP TCP/IP stack.  *   * Author: Adam Dunkels <adam@sics.se>  *  */ #ifndef LWIP_LWIPOPTS_H #define LWIP_LWIPOPTS_H  /*    -----------------------------------------------    ---------- Platform specific locking ----------    ----------------------------------------------- */  /**   * NO_SYS==1: Provides VERY minimal functionality. Otherwise,  * use lwIP facilities.  */ #define NO_SYS                          1  /**  * SYS_LIGHTWEIGHT_PROT==1: if you want inter-task protection for certain  * critical regions during buffer allocation, deallocation and memory  * allocation and deallocation.  */ #define SYS_LIGHTWEIGHT_PROT            0  /*    ------------------------------------    ---------- Memory options ----------    ------------------------------------ */ /**  * MEM_ALIGNMENT: should be set to the alignment of the CPU  *    4 byte alignment -> #define MEM_ALIGNMENT 4  *    2 byte alignment -> #define MEM_ALIGNMENT 2  */ #define MEM_ALIGNMENT                   4  /**  * MEM_SIZE: the size of the heap memory. If the application will send  * a lot of data that needs to be copied, this should be set high.  */ #define MEM_SIZE                        (30 * 1024)  /*    ------------------------------------------------    ---------- Internal Memory Pool Sizes ----------    ------------------------------------------------ */ /**  * MEMP_NUM_PBUF: the number of memp struct pbufs (used for PBUF_ROM and PBUF_REF).  * If the application sends a lot of data out of ROM (or other static memory),  * this should be set high.  */ #define MEMP_NUM_PBUF                   30  /**  * MEMP_NUM_RAW_PCB: Number of raw connection PCBs  * (requires the LWIP_RAW option)  */ #define MEMP_NUM_RAW_PCB                4  /**  * MEMP_NUM_UDP_PCB: the number of UDP protocol control blocks. One  * per active UDP "connection".  * (requires the LWIP_UDP option)  */ #define MEMP_NUM_UDP_PCB                4  /**  * MEMP_NUM_TCP_PCB: the number of simulatenously active TCP connections.  * (requires the LWIP_TCP option)  */ #define MEMP_NUM_TCP_PCB                2  /**  * MEMP_NUM_TCP_PCB_LISTEN: the number of listening TCP connections.  * (requires the LWIP_TCP option)  */ #define MEMP_NUM_TCP_PCB_LISTEN         8  /**  * MEMP_NUM_TCP_SEG: the number of simultaneously queued TCP segments.  * (requires the LWIP_TCP option)  */ #define MEMP_NUM_TCP_SEG                16  /**  * MEMP_NUM_ARP_QUEUE: the number of simulateously queued outgoing  * packets (pbufs) that are waiting for an ARP request (to resolve  * their destination address) to finish.  * (requires the ARP_QUEUEING option)  */ #define MEMP_NUM_ARP_QUEUE              2  /**  * MEMP_NUM_SYS_TIMEOUT: the number of simultaneously active timeouts.  * The default number of timeouts is calculated here for all enabled modules.  * The formula expects settings to be either '0' or '1'.  *  * To this default value, 1 was added for the snmp_increment timer.  */ #define MEMP_NUM_SYS_TIMEOUT            (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + PPP_SUPPORT + (LWIP_IPV6 ? (1 + LWIP_IPV6_REASS + LWIP_IPV6_MLD) : 0)) + 1  /**  * MEMP_NUM_NETBUF: the number of struct netbufs.  * (only needed if you use the sequential API, like api_lib.c)  */ #define MEMP_NUM_NETBUF                 0  /**  * MEMP_NUM_NETCONN: the number of struct netconns.  * (only needed if you use the sequential API, like api_lib.c)  */ #define MEMP_NUM_NETCONN                0  /**  * MEMP_NUM_TCPIP_MSG_API: the number of struct tcpip_msg, which are used  * for callback/timeout API communication.   * (only needed if you use tcpip.c)  */ #define MEMP_NUM_TCPIP_MSG_API          0  /**  * MEMP_NUM_TCPIP_MSG_INPKT: the number of struct tcpip_msg, which are used  * for incoming packets.   * (only needed if you use tcpip.c)  */ #define MEMP_NUM_TCPIP_MSG_INPKT        0  /**  * PBUF_POOL_SIZE: the number of buffers in the pbuf pool.   */ #define PBUF_POOL_SIZE                  32  /**  * MEMP_OVERFLOW_CHECK: Memory pool overflow check switch.  */ #define MEMP_OVERFLOW_CHECK             0  /*    ---------------------------------    ---------- ARP options ----------    --------------------------------- */ /**  * LWIP_ARP==1: Enable ARP functionality.  */ #define LWIP_ARP                        1  /*    --------------------------------    ---------- IP options ----------    -------------------------------- */ /**  * IP_FORWARD==1: Enables the ability to forward IP packets across network  * interfaces. If you are going to run lwIP on a device with only one network  * interface, define this to 0.  */ #define IP_FORWARD                      0  /**  * IP_OPTIONS: Defines the behavior for IP options.  *      IP_OPTIONS==0_ALLOWED: All packets with IP options are dropped.  *      IP_OPTIONS==1_ALLOWED: IP options are allowed (but not parsed).  */ #define IP_OPTIONS_ALLOWED              1  /**  * IP_REASSEMBLY==1: Reassemble incoming fragmented IP packets. Note that  * this option does not affect outgoing packet sizes, which can be controlled  * via IP_FRAG.  */ #define IP_REASSEMBLY                   1  /**  * IP_FRAG==1: Fragment outgoing IP packets if their size exceeds MTU. Note  * that this option does not affect incoming packet sizes, which can be  * controlled via IP_REASSEMBLY.  */ #define IP_FRAG                         1  /**  * IP_REASS_MAXAGE: Maximum time (in multiples of IP_TMR_INTERVAL - so seconds, normally)  * a fragmented IP packet waits for all fragments to arrive. If not all fragments arrived  * in this time, the whole packet is discarded.  */ #define IP_REASS_MAXAGE                 3  /**  * IP_REASS_MAX_PBUFS: Total maximum amount of pbufs waiting to be reassembled.  * Since the received pbufs are enqueued, be sure to configure  * PBUF_POOL_SIZE > IP_REASS_MAX_PBUFS so that the stack is still able to receive  * packets even if the maximum amount of fragments is enqueued for reassembly!  */ #define IP_REASS_MAX_PBUFS              10  /**  * IP_FRAG_USES_STATIC_BUF==1: Use a static MTU-sized buffer for IP  * fragmentation. Otherwise pbufs are allocated and reference the original  * packet data to be fragmented.  */ #define IP_FRAG_USES_STATIC_BUF         0  /**  * IP_DEFAULT_TTL: Default value for Time-To-Live used by transport layers.  */ #define IP_DEFAULT_TTL                  255  /*    ----------------------------------    ---------- ICMP options ----------    ---------------------------------- */ /**  * LWIP_ICMP==1: Enable ICMP module inside the IP stack.  * Be careful, disable that make your product non-compliant to RFC1122  */ #define LWIP_ICMP                       1  /**  * ICMP_TTL: Default value for Time-To-Live used by ICMP packets.  */ #define ICMP_TTL                       (IP_DEFAULT_TTL)  /*    ---------------------------------    ---------- RAW options ----------    --------------------------------- */ /**  * LWIP_RAW==1: Enable application layer to hook into the IP layer itself.  */ #define LWIP_RAW                        1  /*    ----------------------------------    ---------- DHCP options ----------    ---------------------------------- */ /**  * LWIP_DHCP==1: Enable DHCP module.  */ #define LWIP_DHCP                       0  /*    ------------------------------------    ---------- AUTOIP options ----------    ------------------------------------ */ /**  * LWIP_AUTOIP==1: Enable AUTOIP module.  */ #define LWIP_AUTOIP                     0  /*    ----------------------------------    ---------- SNMP options ----------    ---------------------------------- */ /**  * LWIP_SNMP==1: Turn on SNMP module. UDP must be available for SNMP  * transport.  */ #define LWIP_SNMP                       1 #define LWIP_MIB2_CALLBACKS             0 #define MIB2_STATS                      1  /*    ----------------------------------    ---------- IGMP options ----------    ---------------------------------- */ /**  * LWIP_IGMP==1: Turn on IGMP module.   */ #define LWIP_IGMP                       1  /*    ----------------------------------    ---------- DNS options -----------    ---------------------------------- */ /**  * LWIP_DNS==1: Turn on DNS module. UDP must be available for DNS  * transport.  */ #define LWIP_DNS                        0  /*    ---------------------------------    ---------- UDP options ----------    --------------------------------- */ /**  * LWIP_UDP==1: Turn on UDP.  */ #define LWIP_UDP                        1  /**  * LWIP_UDPLITE==1: Turn on UDP-Lite. (Requires LWIP_UDP)  */ #define LWIP_UDPLITE                    0  /**  * UDP_TTL: Default Time-To-Live value.  */ #define UDP_TTL                         (IP_DEFAULT_TTL)  /*    ---------------------------------    ---------- TCP options ----------    --------------------------------- */ /**  * LWIP_TCP==1: Turn on TCP.  */ #define LWIP_TCP                        1 #define TCP_TTL                         255  /* Controls if TCP should queue segments that arrive out of  order. Define to 0 if your device is low on memory. */ #define TCP_QUEUE_OOSEQ                 0  /* TCP Maximum segment size. */ #define TCP_MSS                         (1500 - 40)  /* TCP sender buffer space (bytes). */ #define TCP_SND_BUF                     (4 * TCP_MSS)  /* TCP_SND_QUEUELEN: TCP sender buffer space (pbufs). This must be at    least as much as (2 * TCP_SND_BUF/TCP_MSS) for things to work. */ #define TCP_SND_QUEUELEN                (2 * TCP_SND_BUF / TCP_MSS)  /* TCP receive window. */ #define TCP_WND                         (2 * TCP_MSS)  /*    ----------------------------------    ---------- Pbuf options ----------    ---------------------------------- */ /**  * PBUF_LINK_HLEN: the number of bytes that should be allocated for a  * link level header. The default is 14, the standard value for  * Ethernet.  */ #define PBUF_LINK_HLEN                  16  /*    ------------------------------------    ---------- LOOPIF options ----------    ------------------------------------ */ /**  * LWIP_HAVE_LOOPIF==1: Support loop interface (127.0.0.1) and loopif.c  */ #define LWIP_HAVE_LOOPIF                0  /*    ----------------------------------------------    ---------- Sequential layer options ----------    ---------------------------------------------- */  /**  * LWIP_NETCONN==1: Enable Netconn API (require to use api_lib.c)  */ #define LWIP_NETCONN                    0  /*    ------------------------------------    ---------- Socket options ----------    ------------------------------------ */ /**  * LWIP_SOCKET==1: Enable Socket API (require to use sockets.c)  */ #define LWIP_SOCKET                     0  /*    ----------------------------------------    ---------- Statistics options ----------    ---------------------------------------- */ /**  * LWIP_STATS==1: Enable statistics collection in lwip_stats.  */ #define LWIP_STATS                      1  /* Self-define data. */ /* LWIP MAC address define. */ #define LWIP_MAC_ADDR                   0x11, 0x22, 0x33, 0x44, 0x55, 0x66 /* LWIP net host name define. */ #define LWIP_NETIF_HOSTNAME             1 #define LWIP_NETIF_HOSTNAME_TEXT        "LwIP_Net" /* LWIP use IPV4 address. */ #define LWIP_IPV4                       1 /* Ethernet link speed define. */ #define LWIP_LINK_SPEED_IN_BPS          100000000 /* LWIP gateway, IP address and netmask define. */ #define LWIP_INIT_IPADDR(addr)          IP4_ADDR((addr), 192,168,0,10) #define LWIP_INIT_NETMASK(addr)         IP4_ADDR((addr), 255,255,255,0) #define LWIP_INIT_GW(addr)              IP4_ADDR((addr), 192,168,0,1)  /*    ---------------------------------------    ---------- Debugging options ----------    --------------------------------------- */ #define TAPIF_DEBUG      LWIP_DBG_ON #define TUNIF_DEBUG      LWIP_DBG_OFF #define UNIXIF_DEBUG     LWIP_DBG_OFF #define DELIF_DEBUG      LWIP_DBG_OFF #define SIO_FIFO_DEBUG   LWIP_DBG_OFF #define TCPDUMP_DEBUG    LWIP_DBG_ON #define API_LIB_DEBUG    LWIP_DBG_ON #define API_MSG_DEBUG    LWIP_DBG_ON #define TCPIP_DEBUG      LWIP_DBG_ON #define NETIF_DEBUG      LWIP_DBG_ON #define SOCKETS_DEBUG    LWIP_DBG_ON #define DEMO_DEBUG       LWIP_DBG_ON #define IP_DEBUG         LWIP_DBG_ON #define IP_REASS_DEBUG   LWIP_DBG_ON #define RAW_DEBUG        LWIP_DBG_ON #define ICMP_DEBUG       LWIP_DBG_ON #define UDP_DEBUG        LWIP_DBG_ON #define TCP_DEBUG        LWIP_DBG_ON #define TCP_INPUT_DEBUG  LWIP_DBG_ON #define TCP_OUTPUT_DEBUG LWIP_DBG_ON #define TCP_RTO_DEBUG    LWIP_DBG_ON #define TCP_CWND_DEBUG   LWIP_DBG_ON #define TCP_WND_DEBUG    LWIP_DBG_ON #define TCP_FR_DEBUG     LWIP_DBG_ON #define TCP_QLEN_DEBUG   LWIP_DBG_ON #define TCP_RST_DEBUG    LWIP_DBG_ON  extern unsigned char debug_flags; #define LWIP_DBG_TYPES_ON debug_flags  #endif /* LWIP_LWIPOPTS_H */  

cc.h包含针对处理器和编译器的一些数据类型、字节对齐方式和宏定义等内容。一个例程如下所示：

/*  * Copyright (c) 2001-2003 Swedish Institute of Computer Science.  * All rights reserved.   *   * Redistribution and use in source and binary forms, with or without modification,   * are permitted provided that the following conditions are met:  *  * 1. Redistributions of source code must retain the above copyright notice,  *    this list of conditions and the following disclaimer.  * 2. Redistributions in binary form must reproduce the above copyright notice,  *    this list of conditions and the following disclaimer in the documentation  *    and/or other materials provided with the distribution.  * 3. The name of the author may not be used to endorse or promote products  *    derived from this software without specific prior written permission.   *  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT   * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY   * OF SUCH DAMAGE.  *  * This file is part of the lwIP TCP/IP stack.  *   * Author: Adam Dunkels <adam@sics.se>  *  */ #ifndef LWIP_ARCH_CC_H #define LWIP_ARCH_CC_H  #include <stdio.h> #include <stdint.h>  #define LWIP_NO_STDINT_H        1  /* Define generic types used in lwIP. */ typedef uint8_t   u8_t; typedef int8_t    s8_t; typedef uint16_t  u16_t; typedef int16_t   s16_t; typedef uint32_t  u32_t; typedef int32_t   s32_t; typedef uintptr_t mem_ptr_t; typedef int sys_prot_t;  /* Define (sn)printf formatters for these lwIP types. */ #define X8_F  "02x" #define U16_F "hu" #define S16_F "hd" #define X16_F "hx" #define U32_F "lu" #define S32_F "ld" #define X32_F "lx" #define SZT_F "lu"  /* Little endian mode. */ #define BYTE_ORDER              LITTLE_ENDIAN  /* define compiler specific symbols */ #if defined (__ICCARM__) #define PACK_STRUCT_BEGIN #define PACK_STRUCT_STRUCT #define PACK_STRUCT_END #define PACK_STRUCT_FIELD(x) x #define PACK_STRUCT_USE_INCLUDES  #elif defined (__CC_ARM)  #define PACK_STRUCT_BEGIN __packed #define PACK_STRUCT_STRUCT #define PACK_STRUCT_END #define PACK_STRUCT_FIELD(x) x  #elif defined (__GNUC__)  #define PACK_STRUCT_BEGIN #define PACK_STRUCT_STRUCT __attribute__ ((__packed__)) #define PACK_STRUCT_END #define PACK_STRUCT_FIELD(x) x  #elif defined (__TASKING__)  #define PACK_STRUCT_BEGIN #define PACK_STRUCT_STRUCT #define PACK_STRUCT_END #define PACK_STRUCT_FIELD(x) x  #endif  #define LWIP_PLATFORM_ASSERT(x) do {printf("Assertion failed: ");                                     printf("Assertion failed: ");}while(0)  extern u32_t sys_now(void);   #endif /* LWIP_ARCH_CC_H */  

cc.h文件中声明的sys_now函数需借助处理芯片（如MCU）的定时器实现。

perf.h是与系统统计和测量有关的文件，一般无需求是可不使用。如下所示：

/*  * Copyright (c) 2001-2003 Swedish Institute of Computer Science.  * All rights reserved.   *   * Redistribution and use in source and binary forms, with or without modification,   * are permitted provided that the following conditions are met:  *  * 1. Redistributions of source code must retain the above copyright notice,  *    this list of conditions and the following disclaimer.  * 2. Redistributions in binary form must reproduce the above copyright notice,  *    this list of conditions and the following disclaimer in the documentation  *    and/or other materials provided with the distribution.  * 3. The name of the author may not be used to endorse or promote products  *    derived from this software without specific prior written permission.   *  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT   * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY   * OF SUCH DAMAGE.  *  * This file is part of the lwIP TCP/IP stack.  *   * Author: Adam Dunkels <adam@sics.se>  *  */ #ifndef LWIP_ARCH_PERF_H #define LWIP_ARCH_PERF_H  #define PERF_START    /* null definition */ #define PERF_STOP(x)  /* null definition */  #endif /* LWIP_ARCH_PERF_H */  

2.4 网口驱动开发

网口驱动主要包含两部分的驱动：MAC模块驱动和PHY模块驱动。MAC和PHY位于ISO/OSI模型的最后两层，完成数据链路层和物理层的数据传输。两者之间的具体关系可在网上查询学习，此处不做过多阐述。

2.4.1 MAC模块驱动

一般MAC模块位于MCU中，MCU厂商会提供相应的基本驱动程序，如若没有，则需要开发人员参照Datasheet描述进行编写，必须要实现的接口包括模块初始化、数据发送和数据接收接口。其中模块初始化的基本步骤大致如下：
1、Ethernet端口时钟设置；
2、Ethernet端口引脚设置；
3、MAC模块具体寄存器设置，涉及到MAC地址、接口模式（MII、RMII等）、通信速率、数据接收和发送缓存设置、数据接收和发送模式（轮询、中断或者DMA）等；
4、模块功能（数据接收和发送）启动。

2.4.2 PHY模块驱动

PHY模块通过MII、RMII等连接方式与MAC模块进行连接，在编写驱动时需要参考具体的硬件设计以及PHY芯片数据手册完成驱动操作。可参考如下步骤进行：
1、PHY芯片电源控制，按照硬件电路设计完成对PHY芯片上电和下电的驱动控制；
2、参考PHY芯片数据手册完成初始化设置，具体配置信息根据PHY芯片的不同或有差异，但是主要目的都是为了打通网络数据的传输链路。

开发人员可能会发现，有的硬件电路设计中找不到PHY芯片，与处理器MAC模块的通信连接可能会被叫做Switch芯片的模块代替，此处要说明的是Switch常用于多网口的电路设计中，由于Switch芯片内部集成了多个MAC和PHY模块，可完成数据在多路网口之间的数据传输。此时只需参照PHY芯片的驱动开发步骤完成Switch芯片的驱动的开发。当然，Switch芯片的功能要比PHY芯片的功能复杂，驱动支持接口可能会相对较多，开发人员需根据使用需求选择具体开发哪些功能驱动。

网口驱动开发一旦完成，便保证了网络数据的传输链路已经打通，在移植过程中便不用再担心硬件导致的LwIP数据传输不成功问题了，接下来便是将网口驱动程序加入到LwIP协议栈中的工作。

2.5 LwIP网卡接口适配

LwIP网卡驱动适配工作主要是完善“lwip-2.0.3srcnetifethernetif.c”文件中部分函数接口，包括以下函数：
low_level_init
low_level_output
low_level_input
在low_level_init函数中应当完成MAC地址的设置，同时调用网口驱动初始化函数，完成网络的初始化工作，low_level_init函数中已经指示了应当在哪些地方进行修改，下述代码是移植过程中的一个实例，其中带有“Add by myself start ”和“Add by myself end”注释部分是移植过程中添加的完善代码；

static void low_level_init(struct netif *netif) {   struct ethernetif *ethernetif = netif->state;   /* Add by myself start */   uint8_t aMacAddr[6] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66};   /* Add by myself end */    /* set MAC hardware address length */   netif->hwaddr_len = ETHARP_HWADDR_LEN;    /* Add by myself start */   /* set MAC hardware address */   netif->hwaddr[0] = aMacAddr[0];   netif->hwaddr[1] = aMacAddr[1];   netif->hwaddr[2] = aMacAddr[2];   netif->hwaddr[3] = aMacAddr[3];   netif->hwaddr[4] = aMacAddr[4];   netif->hwaddr[5] = aMacAddr[5];   /* Add by myself end */    /* maximum transfer unit */   netif->mtu = 1500;    /* Add by myself start */   /* Device ethernet port set. */   netif->num = ETHERNET_PORT0;   /* Add by myself end*/    /* device capabilities */   /* don't set NETIF_FLAG_ETHARP if this device is not an ethernet one */   netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP; #if LWIP_IPV6 && LWIP_IPV6_MLD   /*    * For hardware/netifs that implement MAC filtering.    * All-nodes link-local is handled by default, so we must let the hardware know    * to allow multicast packets in.    * Should set mld_mac_filter previously. */   if (netif->mld_mac_filter != NULL) {     ip6_addr_t ip6_allnodes_ll;      ip6_addr_set_allnodes_linklocal(&ip6_allnodes_ll);     netif->mld_mac_filter(netif, &ip6_allnodes_ll, NETIF_ADD_MAC_FILTER);   } #endif /* LWIP_IPV6 && LWIP_IPV6_MLD */    /* Do whatever else is needed to initialize interface. */   /* Add by myself start */   DevEthernetInit(netif->num);   /* Add by myself end*/ } 

在low_level_output函数中调用网卡数据发送接口，完成网络数据的发送工作，low_level_output函数中已经指示了应当在哪些地方进行修改，下述代码是移植过程中的一个实例，其中带有“Add by myself start ”和“Add by myself end”注释部分是移植过程中添加的完善代码；

static err_t low_level_output(struct netif *netif, struct pbuf *p) {   struct ethernetif *ethernetif = netif->state;   struct pbuf *q;  //  initiate transfer();  #if ETH_PAD_SIZE   pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */ #endif    for (q = p; q != NULL; q = q->next) {     /* Send the data from the pbuf to the interface, one pbuf at a        time. The size of the data in each pbuf is kept in the ->len        variable. */ //    send data from(q->payload, q->len);       /* Add by myself start */       DevEthernetSend(netif->num, q->payload, q->len);       /* Add by myself end */   }  //  signal that packet should be sent();    MIB2_STATS_NETIF_ADD(netif, ifoutoctets, p->tot_len);   if (((u8_t*)p->payload)[0] & 1) {     /* broadcast or multicast packet*/     MIB2_STATS_NETIF_INC(netif, ifoutnucastpkts);   } else {     /* unicast packet */     MIB2_STATS_NETIF_INC(netif, ifoutucastpkts);   }   /* increase ifoutdiscards or ifouterrors on error */  #if ETH_PAD_SIZE   pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */ #endif    LINK_STATS_INC(link.xmit);    return ERR_OK; } 

在low_level_input函数中调用网卡数据接收接口，完成网络数据的接收工作，low_level_input函数中已经指示了应当在哪些地方进行修改，下述代码是移植过程中的一个实例，其中带有“Add by myself start ”和“Add by myself end”注释部分是移植过程中添加的完善代码；

static struct pbuf * low_level_input(struct netif *netif) {   struct ethernetif *ethernetif = netif->state;   struct pbuf *p, *q;   u16_t len;   /* Add by myself start */   uint8_t *pFrame = NULL;   /* Add by myself end */    /* Obtain the size of the packet and put it into the "len"      variable. */   /* Add by myself start */   len = DevEthernetGetRecvLength(netif->num);   /* Add by myself end */  #if ETH_PAD_SIZE   len += ETH_PAD_SIZE; /* allow room for Ethernet padding */ #endif    /* We allocate a pbuf chain of pbufs from the pool. */   p = pbuf_alloc(PBUF_RAW, len, PBUF_POOL);    if (p != NULL) {  #if ETH_PAD_SIZE     pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */ #endif      /* We iterate over the pbuf chain until we have read the entire      * packet into the pbuf. */     for (q = p; q != NULL; q = q->next) {       /* Read enough bytes to fill this pbuf in the chain. The        * available data in the pbuf is given by the q->len        * variable.        * This does not necessarily have to be a memcpy, you can also preallocate        * pbufs for a DMA-enabled MAC and after receiving truncate it to the        * actually received size. In this case, ensure the tot_len member of the        * pbuf is the sum of the chained pbuf len members.        */       //read data into(q->payload, q->len);       /* Add by myself start */       /* Receive data from MCU ethernet port. */       pFrame = (uint8_t *)DevEthernetRecv(netif->num);       if (NULL != pFrame)       {           memcpy((uint8_t *)q->payload, pFrame, len);       }       /* Add by myself end */     }     //acknowledge that packet has been read();     /* Add by myself start */     DevEthernetFreeRecvBuf(netif->num);     /* Add by myself end */      MIB2_STATS_NETIF_ADD(netif, ifinoctets, p->tot_len);     if (((u8_t*)p->payload)[0] & 1) {       /* broadcast or multicast packet*/       MIB2_STATS_NETIF_INC(netif, ifinnucastpkts);     } else {       /* unicast packet*/       MIB2_STATS_NETIF_INC(netif, ifinucastpkts);     } #if ETH_PAD_SIZE     pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */ #endif      LINK_STATS_INC(link.recv);   } else {     drop packet();     LINK_STATS_INC(link.memerr);     LINK_STATS_INC(link.drop);     MIB2_STATS_NETIF_INC(netif, ifindiscards);   }    return p; } 

上述接口完善结束，意味着离LwIP裸机移植的成功又进了一步，接下来便是想办法将LwIP协议栈调度运行起来，测试运行效果。

2.6 LwIP运行和测试

在调度运行LwIP之前还需完成两个重要的接口：LwIP_Init和LwIP_Test。
LwIP_Init用于完成LwIP协议栈的初始化工作，如网关设置、IP地址设置、子网掩码设置、初始化处理和网络链接启动等。有关网关、IP地址和子网掩码等信息的配置已在lwipopts.h文件中体现，如下所示：

/* Self-define data. */ /* LWIP MAC address define. */ #define LWIP_MAC_ADDR                   0x11, 0x22, 0x33, 0x44, 0x55, 0x66 /* LWIP net host name define. */ #define LWIP_NETIF_HOSTNAME             1 #define LWIP_NETIF_HOSTNAME_TEXT        "LwIP_Net" /* LWIP use IPV4 address. */ #define LWIP_IPV4                       1 /* Ethernet link speed define. */ #define LWIP_LINK_SPEED_IN_BPS          100000000 /* LWIP gateway, IP address and netmask define. */ #define LWIP_INIT_IPADDR(addr)          IP4_ADDR((addr), 192,168,0,10) #define LWIP_INIT_NETMASK(addr)         IP4_ADDR((addr), 255,255,255,0) #define LWIP_INIT_GW(addr)              IP4_ADDR((addr), 192,168,0,1) 

LwIP_Init函数的实现例程如下所示：

void LwIP_Init(void) { #if LWIP_IPV4     ip4_addr_t ipaddr, netmask, gw; #if (!LWIP_DHCP) && (!LWIP_AUTOIP)     LWIP_INIT_GW(&gw);     LWIP_INIT_IPADDR(&ipaddr);     LWIP_INIT_NETMASK(&netmask); #endif /* (!LWIP_DHCP) && (!LWIP_AUTOIP) */ #endif /* LWIP_IPV4 */      /* LwIP service init process. */     lwip_init();      /* Config netif layer parameters. */     netif_set_default(netif_add(&gnetif, &ipaddr, &netmask, &gw, NULL, ethernetif_init, netif_input));      /* Check to set netif up flag. */     if (netif_is_link_up(&gnetif))     {         /* If netif link is fully configured, this function must be called. */         netif_set_up(&gnetif);     }     else     {         /* If netif link is down, this function must be called. */         netif_set_down(&gnetif);     } } 

LwIP_Test函数则用于接收网络数据和监测LwIP的timeout事件，此函数要周期性地被调用，保证网络模块接收到的网络数据及时传入LwIP协议栈中进行处理。LwIP_Test函数示例如下所示：

void LwIPTestProcess(void) {     /* Ethernet data receiving process. */     ethernetif_input(&gnetif);          /* Check LwIP timeout event. */     sys_check_timeouts(); } 

进行到这一步，LwIP裸机移植工作已全部完成，如无意外，此时应当可以通过电脑端cmd窗口与烧录了LwIP程序的硬件开发板进行ping通信，前提是需设置电脑IPv4的网关地址、IP地址和子网掩码，保证电脑和开发板在同一IP段内。