开发背景：

1、主芯片—STM32F207VCT6；

2、TCP/IP协议栈—LWIP，依托ST例程移植；

3、操作系统—无（裸机）；

异常现象：

1、网线不插入的情况下先给设备上电，之后再插入网线无法ping通；（如果上电前网线插入，网络正常）；

2、网络已经正常的情况下，电脑PC端修改传输模式（比如从原来的100M全双工修改为10M全双工）导致网络不通；

原因分析：

1、针对第一种异常情况，是由于上电时网线未插入，导致ETH初始化部分未能成功完成，之后即使再插入网线，程序中没有再次进行初始化的逻辑补充，从而导致网络异常；

2、针对第二种情况，情况是上电时完成了ETH的初始化并与PC协商成功，此时网络正常。但当PC端修改传输模式后，程序中未能执行再次协商与MAC的初始化工作，导致网络异常；

解决方法：

首先，要明确上述问题的关键点所在，所有的异常均是网线的拔插导致（PC端修改连接传输方式时也相当于网线的拔掉重插），因此主程序中必须要有对当前网络连接与断开的检测或者利用PHY芯片的中断引脚；

其次，无论利用轮询或是PHY中断配置引脚，根本的原理都是一样的，就是感知到网络的连接与断开，下面给出采用的查询方式：

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){/*检测插拔中断*/

uint16_t status = ETH_ReadPHYRegister(DP83848_PHY_ADDRESS, PHY_BSR);

if(status & (PHY_AutoNego_Complete | PHY_Linked_Status)){/*检测到网线连接*/

if(EthInitStatus == 0){/*之前未成功初始化过*/

/*Reinit PHY*/

ETH_Reinit();

}

else{/*之前已经成功初始化*/

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

netif_set_link_up(netif);

}

}

else{/*网线断开*/

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

netif_set_link_down(netif);

}

}

}

备注说明：将该检测函数放入主循环，程序中标注的部分为解决网线热拔插问题的关键点。

1、标注红色的部分执行的条件是检测到网线插入且之前ETH部分未成功初始化过（即之前一直处在上电但网线未插入）的情况，此时需要对ETH重新初始化，从而解决异常现象的第一种情况，具体执行内容为：

/**

* @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已设为全局结构体；

2、标注蓝色部分的执行条件是已经成功初始化过ETH，但之后出现了网线的拔插情况，此时需要在每次检测到网络连接时重新进行自协商并初始化MAC，具体的执行流程如下介绍：

A、检测到该条件时，首先调用：

netif_set_link_up(netif);

netif_set_link_down(netif);

B、追溯两个函数的定义处，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：从上述看出，若要这两个函数有效编译，则必须定义宏LWIP_NETIF_LINK_CALLBACK 为1，请自行设置；

II：函数netif_set_link_callback的作用是指定网络连接发生改变时的回调函数；

III：详细的讲一下主要思路，Eth_Link_ITHandler执行中检测到网线拔插时分别调用netif_set_link_up(netif)、netif_set_link_down(netif);这两个函数的调用会引发netif_set_link_callback的执行，从而执行指定的网络连接或断开的回调函数；

Ⅳ：通过netif_set_link_callback该函数在LWIP初始化的时候指定网络连接变化的回调函数，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，回调函数eth_re_link的具体内容如下，实现网络拔插后的重新自协商与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;

/*----------------------- ETHERNET MACFCR Configuration --------------------*/

/* Get the ETHERNET MACFCR value */

tmpreg = ETH->MACFCR;

/* Clear xx bits */

tmpreg &= MACFCR_CLEAR_MASK;

/* Set the PT bit according to ETH_PauseTime value */

/* Set the DZPQ bit according to ETH_ZeroQuantaPause value */

/* Set the PLT bit according to ETH_PauseLowThreshold value */

/* Set the UP bit according to ETH_UnicastPauseFrameDetect value */

/* Set the RFE bit according to ETH_ReceiveFlowControl value */

/* Set the TFE bit according to ETH_TransmitFlowControl value */

tmpreg |= (uint32_t)((ETH_InitStructure.ETH_PauseTime << 16) |

ETH_InitStructure.ETH_ZeroQuantaPause |

ETH_InitStructure.ETH_PauseLowThreshold |

ETH_InitStructure.ETH_UnicastPauseFrameDetect |

ETH_InitStructure.ETH_ReceiveFlowControl |

ETH_InitStructure.ETH_TransmitFlowControl);

/* Write to ETHERNET MACFCR */

ETH->MACFCR = (uint32_t)tmpreg;

/*----------------------- ETHERNET MACVLANTR Configuration -----------------*/

/* Set the ETV bit according to ETH_VLANTagComparison value */

/* Set the VL bit according to ETH_VLANTagIdentifier value */

ETH->MACVLANTR = (uint32_t)(ETH_InitStructure.ETH_VLANTagComparison |

ETH_InitStructure.ETH_VLANTagIdentifier);

/*-------------------------------- DMA Config ------------------------------*/

/*----------------------- ETHERNET DMAOMR Configuration --------------------*/

/* Get the ETHERNET DMAOMR value */

tmpreg = ETH->DMAOMR;

/* Clear xx bits */

tmpreg &= DMAOMR_CLEAR_MASK;

/* Set the DT bit according to ETH_DropTCPIPChecksumErrorFrame value */

/* Set the RSF bit according to ETH_ReceiveStoreForward value */

/* Set the DFF bit according to ETH_FlushReceivedFrame value */

/* Set the TSF bit according to ETH_TransmitStoreForward value */

/* Set the TTC bit according to ETH_TransmitThresholdControl value */

/* Set the FEF bit according to ETH_ForwardErrorFrames value */

/* Set the FUF bit according to ETH_ForwardUndersizedGoodFrames value */

/* Set the RTC bit according to ETH_ReceiveThresholdControl value */

/* Set the OSF bit according to ETH_SecondFrameOperate value */

tmpreg |= (uint32_t)(ETH_InitStructure.ETH_DropTCPIPChecksumErrorFrame |

ETH_InitStructure.ETH_ReceiveStoreForward |

ETH_InitStructure.ETH_FlushReceivedFrame |

ETH_InitStructure.ETH_TransmitStoreForward |

ETH_InitStructure.ETH_TransmitThresholdControl |

ETH_InitStructure.ETH_ForwardErrorFrames |

ETH_InitStructure.ETH_ForwardUndersizedGoodFrames |

ETH_InitStructure.ETH_ReceiveThresholdControl |

ETH_InitStructure.ETH_SecondFrameOperate);

/* Write to ETHERNET DMAOMR */

ETH->DMAOMR = (uint32_t)tmpreg;

/*----------------------- ETHERNET DMABMR Configuration --------------------*/

/* Set the AAL bit according to ETH_AddressAlignedBeats value */

/* Set the FB bit according to ETH_FixedBurst value */

/* Set the RPBL and 4*PBL bits according to ETH_RxDMABurstLength value */

/* Set the PBL and 4*PBL bits according to ETH_TxDMABurstLength value */

/* Set the DSL bit according to ETH_DesciptorSkipLength value */

/* Set the PR and DA bits according to ETH_DMAArbitration value */

ETH->DMABMR = (uint32_t)(ETH_InitStructure.ETH_AddressAlignedBeats |

ETH_InitStructure.ETH_FixedBurst |

ETH_InitStructure.ETH_RxDMABurstLength | /* !! if 4xPBL is selected for Tx or Rx it is applied for the other */

ETH_InitStructure.ETH_TxDMABurstLength |

(ETH_InitStructure.ETH_DescriptorSkipLength << 2) |

ETH_InitStructure.ETH_DMAArbitration |

ETH_DMABMR_USP); /* Enable use of separate PBL for Rx and Tx */

#ifdef USE_ENHANCED_DMA_DESCRIPTORS

/* Enable the Enhanced DMA descriptors */

ETH->DMABMR |= ETH_DMABMR_EDE;

#endif /* USE_ENHANCED_DMA_DESCRIPTORS */

/* Return Ethernet configuration success */

// return ETH_SUCCESS;

// ETH_Start();

}

else{/*link down process*/

}

}

至此，对于STM32F207（裸机）- LWIP网线热插入网络不通遇到的问题以及解决办法介绍完毕。