開(kāi)發(fā)背景：

1、主芯片—STM32F207VCT6；

2、TCP/IP協(xié)議棧—LWIP，依托ST例程移植；

3、操作系統(tǒng)—無(wú)（裸機(jī)）；

異?，F(xiàn)象：

1、網(wǎng)線不插入的情況下先給設(shè)備上電，之后再插入網(wǎng)線無(wú)法ping通；（如果上電前網(wǎng)線插入，網(wǎng)絡(luò)正常）；

2、網(wǎng)絡(luò)已經(jīng)正常的情況下，電腦PC端修改傳輸模式（比如從原來(lái)的100M全雙工修改為10M全雙工）導(dǎo)致網(wǎng)絡(luò)不通；

原因分析：

1、針對(duì)第一種異常情況，是由于上電時(shí)網(wǎng)線未插入，導(dǎo)致ETH初始化部分未能成功完成，之后即使再插入網(wǎng)線，程序中沒(méi)有再次進(jìn)行初始化的邏輯補(bǔ)充，從而導(dǎo)致網(wǎng)絡(luò)異常；

2、針對(duì)第二種情況，情況是上電時(shí)完成了ETH的初始化并與PC協(xié)商成功，此時(shí)網(wǎng)絡(luò)正常。但當(dāng)PC端修改傳輸模式后，程序中未能執(zhí)行再次協(xié)商與MAC的初始化工作，導(dǎo)致網(wǎng)絡(luò)異常；

解決方法：

首先，要明確上述問(wèn)題的關(guān)鍵點(diǎn)所在，所有的異常均是網(wǎng)線的拔插導(dǎo)致（PC端修改連接傳輸方式時(shí)也相當(dāng)于網(wǎng)線的拔掉重插），因此主程序中必須要有對(duì)當(dāng)前網(wǎng)絡(luò)連接與斷開(kāi)的檢測(cè)或者利用PHY芯片的中斷引腳；

其次，無(wú)論利用輪詢或是PHY中斷配置引腳，根本的原理都是一樣的，就是感知到網(wǎng)絡(luò)的連接與斷開(kāi)，下面給出采用的查詢方式：

void Eth_Link_ITHandler(struct netif *netif)

{

/* Check whether the link interrupt has occurred or not */

if(((ETH_ReadPHYRegister(DP83848_PHY_ADDRESS, PHY_MISR)) & PHY_LINK_STATUS) != 0){/*檢測(cè)插拔中斷*/

uint16_t status = ETH_ReadPHYRegister(DP83848_PHY_ADDRESS, PHY_BSR);

if(status & (PHY_AutoNego_Complete | PHY_Linked_Status)){/*檢測(cè)到網(wǎng)線連接*/

if(EthInitStatus == 0){/*之前未成功初始化過(guò)*/

/*Reinit PHY*/

ETH_Reinit();

}

else{/*之前已經(jīng)成功初始化*/

/*set link up for re link callbalk function*/

netif_set_link_up(netif);

}

}

else{/*網(wǎng)線斷開(kāi)*/

/*set link down for re link callbalk function*/

netif_set_link_down(netif);

}

}

}

備注說(shuō)明：將該檢測(cè)函數(shù)放入主循環(huán)，程序中標(biāo)注的部分為解決網(wǎng)線熱拔插問(wèn)題的關(guān)鍵點(diǎn)。

1、標(biāo)注紅色的部分執(zhí)行的條件是檢測(cè)到網(wǎng)線插入且之前ETH部分未成功初始化過(guò)（即之前一直處在上電但網(wǎng)線未插入）的情況，此時(shí)需要對(duì)ETH重新初始化，從而解決異常現(xiàn)象的第一種情況，具體執(zhí)行內(nèi)容為：

/**

* @brief : first time power on but init failed, do again

* @param : None

*

* @retval : None

* @author : xuk

*/

void ETH_Reinit(void){

/* Configure Ethernet */

EthInitStatus =ETH_Init(Ð_InitStructure, DP83848_PHY_ADDRESS);

}

其中ETH_InitStructure已設(shè)為全局結(jié)構(gòu)體；

2、標(biāo)注藍(lán)色部分的執(zhí)行條件是已經(jīng)成功初始化過(guò)ETH，但之后出現(xiàn)了網(wǎng)線的拔插情況，此時(shí)需要在每次檢測(cè)到網(wǎng)絡(luò)連接時(shí)重新進(jìn)行自協(xié)商并初始化MAC，具體的執(zhí)行流程如下介紹：

A、檢測(cè)到該條件時(shí)，首先調(diào)用：

netif_set_link_up(netif);

netif_set_link_down(netif);

B、追溯兩個(gè)函數(shù)的定義處，如下：

#if LWIP_NETIF_LINK_CALLBACK

/**

* Called by a driver when its link goes up

*/

void netif_set_link_up(struct netif *netif )

{

netif->flags |= NETIF_FLAG_LINK_UP;

#if LWIP_DHCP

if (netif->dhcp) {

dhcp_network_changed(netif);

}

#endif /* LWIP_DHCP */

#if LWIP_AUTOIP

if (netif->autoip) {

autoip_network_changed(netif);

}

#endif /* LWIP_AUTOIP */

if (netif->flags & NETIF_FLAG_UP) {

#if LWIP_ARP

/* For Ethernet network interfaces, we would like to send a "gratuitous ARP" */

if (netif->flags & NETIF_FLAG_ETHARP) {

etharp_gratuitous(netif);

}

#endif /* LWIP_ARP */

#if LWIP_IGMP

/* resend IGMP memberships */

if (netif->flags & NETIF_FLAG_IGMP) {

igmp_report_groups( netif);

}

#endif /* LWIP_IGMP */

}

NETIF_LINK_CALLBACK(netif);

}

/**

* Called by a driver when its link goes down

*/

void netif_set_link_down(struct netif *netif )

{

netif->flags &= ~NETIF_FLAG_LINK_UP;

NETIF_LINK_CALLBACK(netif);

}

/**

* Ask if a link is up

*/

u8_t netif_is_link_up(struct netif *netif)

{

return (netif->flags & NETIF_FLAG_LINK_UP) ? 1 : 0;

}

/**

* Set callback to be called when link is brought up/down

*/

voidnetif_set_link_callback(struct netif *netif, void (* link_callback)(struct netif *netif ))

{

if (netif) {

netif->link_callback = link_callback;

}

}

#endif /* LWIP_NETIF_LINK_CALLBACK */

注意：I：從上述看出，若要這兩個(gè)函數(shù)有效編譯，則必須定義宏LWIP_NETIF_LINK_CALLBACK 為1，請(qǐng)自行設(shè)置；

II：函數(shù)netif_set_link_callback的作用是指定網(wǎng)絡(luò)連接發(fā)生改變時(shí)的回調(diào)函數(shù)；

III：詳細(xì)的講一下主要思路，Eth_Link_ITHandler執(zhí)行中檢測(cè)到網(wǎng)線拔插時(shí)分別調(diào)用netif_set_link_up(netif)、netif_set_link_down(netif);這兩個(gè)函數(shù)的調(diào)用會(huì)引發(fā)netif_set_link_callback的執(zhí)行，從而執(zhí)行指定的網(wǎng)絡(luò)連接或斷開(kāi)的回調(diào)函數(shù)；

Ⅳ：通過(guò)netif_set_link_callback該函數(shù)在LWIP初始化的時(shí)候指定網(wǎng)絡(luò)連接變化的回調(diào)函數(shù)，可放置如下位置：

void LwIP_Init(void){

......

......

......

......

/*set the link up or link down callback function - xuk*/

netif_set_link_callback(&netif,eth_re_link);

}

其中，回調(diào)函數(shù)eth_re_link的具體內(nèi)容如下，實(shí)現(xiàn)網(wǎng)絡(luò)拔插后的重新自協(xié)商與MAC初始化：

/**

* @brief : process the relink of eth

* @param : netif - - specify the ETH netif

*

* @retval : none

* @author : xuk

*/

voideth_re_link(struct netif *netif){

__IO uint32_t tickstart = 0;

uint32_t regvalue = 0, tmpreg = 0;

if(netif_is_link_up(netif)){/*link up process*/

if(ETH_InitStructure.ETH_AutoNegotiation == ETH_AutoNegotiation_Enable){/*AutoNegotiation_Enable*/

/* Enable Auto-Negotiation */

ETH_WritePHYRegister(DP83848_PHY_ADDRESS, PHY_BCR, PHY_AutoNegotiation);

/* Wait until the auto-negotiation will be completed */

do

{

tickstart++;

} while (!(ETH_ReadPHYRegister(DP83848_PHY_ADDRESS, PHY_BSR) & PHY_AutoNego_Complete) && (tickstart < (uint32_t)PHY_READ_TO));

/* Return ERROR in case of timeout */

if(tickstart == PHY_READ_TO)

{

// return ETH_ERROR;

}

/* Reset Timeout counter */

tickstart = 0;

/* Read the result of the auto-negotiation */

regvalue = ETH_ReadPHYRegister(DP83848_PHY_ADDRESS, PHY_SR);

/* Configure the MAC with the Duplex Mode fixed by the auto-negotiation process */

if((regvalue & PHY_DUPLEX_STATUS) != (uint32_t)RESET)

{

/* Set Ethernet duplex mode to Full-duplex following the auto-negotiation */

ETH_InitStructure.ETH_Mode = ETH_Mode_FullDuplex;

}

else

{

/* Set Ethernet duplex mode to Half-duplex following the auto-negotiation */

ETH_InitStructure.ETH_Mode = ETH_Mode_HalfDuplex;

}

/* Configure the MAC with the speed fixed by the auto-negotiation process */

if(regvalue & PHY_SPEED_STATUS)

{

/* Set Ethernet speed to 10M following the auto-negotiation */

ETH_InitStructure.ETH_Speed = ETH_Speed_10M;

}

else

{

/* Set Ethernet speed to 100M following the auto-negotiation */

ETH_InitStructure.ETH_Speed = ETH_Speed_100M;

}

}

else{/*AutoNegotiation_Disable*/

if(!ETH_WritePHYRegister(DP83848_PHY_ADDRESS, PHY_BCR, ((uint16_t)(ETH_InitStructure.ETH_Mode >> 3) |

(uint16_t)(ETH_InitStructure.ETH_Speed >> 1))))

{

/* Return ERROR in case of write timeout */

// return ETH_ERROR;

}

/* Delay to assure PHY configuration */

// _eth_delay_(PHY_CONFIG_DELAY);

}

/*------------------------ ETHERNET MACCR Configuration --------------------*/

/* Get the ETHERNET MACCR value */

tmpreg = ETH->MACCR;

/* Clear WD, PCE, PS, TE and RE bits */

tmpreg &= MACCR_CLEAR_MASK;

/* Set the WD bit according to ETH_Watchdog value */

/* Set the JD: bit according to ETH_Jabber value */

/* Set the IFG bit according to ETH_InterFrameGap value */

/* Set the DCRS bit according to ETH_CarrierSense value */

/* Set the FES bit according to ETH_Speed value */

/* Set the DO bit according to ETH_ReceiveOwn value */

/* Set the LM bit according to ETH_LoopbackMode value */

/* Set the DM bit according to ETH_Mode value */

/* Set the IPCO bit according to ETH_ChecksumOffload value */

/* Set the DR bit according to ETH_RetryTransmission value */

/* Set the ACS bit according to ETH_AutomaticPadCRCStrip value */

/* Set the BL bit according to ETH_BackOffLimit value */

/* Set the DC bit according to ETH_DeferralCheck value */

tmpreg |= (uint32_t)(ETH_InitStructure.ETH_Watchdog |

ETH_InitStructure.ETH_Jabber |

ETH_InitStructure.ETH_InterFrameGap |

ETH_InitStructure.ETH_CarrierSense |

ETH_InitStructure.ETH_Speed |

ETH_InitStructure.ETH_ReceiveOwn |

ETH_InitStructure.ETH_LoopbackMode |

ETH_InitStructure.ETH_Mode |

ETH_InitStructure.ETH_ChecksumOffload |

ETH_InitStructure.ETH_RetryTransmission |

ETH_InitStructure.ETH_AutomaticPadCRCStrip |

ETH_InitStructure.ETH_BackOffLimit |

ETH_InitStructure.ETH_DeferralCheck);

/* Write to ETHERNET MACCR */

ETH->MACCR = (uint32_t)tmpreg;

/*----------------------- ETHERNET MACFFR Configuration --------------------*/

/* Set the RA bit according to ETH_ReceiveAll value */

/* Set the SAF and SAIF bits according to ETH_SourceAddrFilter value */

/* Set the PCF bit according to ETH_PassControlFrames value */

/* Set the DBF bit according to ETH_BroadcastFramesReception value */

/* Set the DAIF bit according to ETH_DestinationAddrFilter value */

/* Set the PR bit according to ETH_PromiscuousMode value */

/* Set the PM, HMC and HPF bits according to ETH_MulticastFramesFilter value */

/* Set the HUC and HPF bits according to ETH_UnicastFramesFilter value */

/* Write to ETHERNET MACFFR */

ETH->MACFFR = (uint32_t)(ETH_InitStructure.ETH_ReceiveAll |

ETH_InitStructure.ETH_SourceAddrFilter |

ETH_InitStructure.ETH_PassControlFrames |

ETH_InitStructure.ETH_BroadcastFramesReception |

ETH_InitStructure.ETH_DestinationAddrFilter |

ETH_InitStructure.ETH_PromiscuousMode |

ETH_InitStructure.ETH_MulticastFramesFilter |

ETH_InitStructure.ETH_UnicastFramesFilter);

/*--------------- ETHERNET MACHTHR and MACHTLR Configuration ---------------*/

/* Write to ETHERNET MACHTHR */

ETH->MACHTHR = (uint32_t)ETH_InitStructure.ETH_HashTableHigh;

/* Write to ETHERNET MACHTLR */

ETH->MACHTLR = (uint32_t)ETH_InitStructure.ETH_HashTableLow;

/*-----------------------