一目了然
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-2.0.3\src”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-2.0.3\src\api”中的所有文件；
工程core目录：添加“lwip-2.0.3\src\core”中除“ipv6”外的所有文件和目录；
工程netif目录：添加“lwip-2.0.3\src\netif”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-2.0.3\src\include”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“include\arch”目录。将“contrib-2.0.1\ports\unix\minimal”目录下的“lwipopts.h”文件添加至工程“port\include”目录中，将“contrib-2.0.1\ports\unix\port\include\arch”目录下“cc.h”和“perf.h”文件添加至工程目录“port\include\arch”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-2.0.3\src\netif\ethernetif.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端内。