--- title: "Implement DHCP automatic IP address acquisition function based on W5500 chip" url: "https://maker.wiznet.io/ronpang/projects/implement-dhcp-automatic-ip-address-acquisition-function-based-on-w5500-chip/" markdown_url: "https://maker.wiznet.io/ronpang/projects/implement-dhcp-automatic-ip-address-acquisition-function-based-on-w5500-chip/md" type: "UCC: User Created Content" author: "alloutlove" author_url: "https://www.cnblogs.com/ll55522201/p/19187104" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "alloutlove" original_url: "https://www.cnblogs.com/ll55522201/p/19187104" published: "2026-01-06" language: "en" likes: 0 views: 415 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # Implement DHCP automatic IP address acquisition function based on W5500 chip > Implement DHCP automatic IP address acquisition function based on W5500 chip Original author: alloutlove (source: https://www.cnblogs.com/ll55522201/p/19187104) ## Article ## [**Implement DHCP automatic IP address acquisition function based on W5500 chip**](https://www.cnblogs.com/ll55522201/p/19187104) #### **I. Hardware** ##### **1. Circuit connection** | **W5500 pin** | **STM32 pin** | **Function Description** | | --- | --- | --- | | SCLK | PA5 | SPI clock | | MOSI | PA7 | The main one goes out, the secondary one comes in. | | MISO | PA6 | The main enters, the secondary exits | | CS | PA4 | Chip select signal | | INT | PA3 | Interrupt pin | | RESET | PA2 | Reset pin | | 3.3V | 3.3V | power supply | | GND | GND | ground wire | ##### **2. Network Topology** ```css [STM32] --SPI--> [W5500] --RJ45--> 局域网交换机 ↑ DHCP服务器 ``` --- #### **II. Software Implementation Steps** ##### **1. Register initialization** ```c // W5500复位配置 void W5500_Reset() { GPIO_ResetBits(GPIOA, GPIO_Pin_2); // 拉低RESET引脚 Delay_ms(100); GPIO_SetBits(GPIOA, GPIO_Pin_2); // 释放RESET Delay_ms(200); } // SPI接口配置（STM32 HAL库） SPI_HandleTypeDef hspi1; void MX_SPI1_Init(void) { hspi1.Instance = SPI1; hspi1.Init.Mode = SPI_MODE_MASTER; hspi1.Init.Direction = SPI_DIRECTION_2LINES; hspi1.Init.DataSize = SPI_DATASIZE_8BIT; hspi1.Init.CLKPolarity = SPI_POLARITY_LOW; hspi1.Init.CLKPhase = SPI_PHASE_1EDGE; hspi1.Init.NSS = SPI_NSS_SOFT; hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256; HAL_SPI_Init(&hspi1); } ``` ##### **2. DHCP State Machine Implementation** ```c typedef enum { DHCP_INIT, DHCP_DISCOVER, DHCP_OFFER, DHCP_REQUEST, DHCP_ACK, DHCP_TIMEOUT } DHCP_State; DHCP_State dhcp_state = DHCP_INIT; uint8_t dhcp_mac[6] = {0x00, 0x08, 0xDC, 0x12, 0x34, 0x56}; // 默认MAC地址 void DHCP_Init() { // 设置MAC地址 setSHAR(dhcp_mac); // 配置网络模式为DHCP setNETINFO(NETINFO_DHCP); // 初始化DHCP定时器 HAL_TIM_Base_Start_IT(&htim3); // 100ms定时器 } void DHCP_Process() { switch(dhcp_state) { case DHCP_INIT: send_DHCP_Discover(); dhcp_state = DHCP_DISCOVER; break; case DHCP_DISCOVER: if(receive_DHCP_Offer()) { dhcp_state = DHCP_OFFER; } break; case DHCP_OFFER: send_DHCP_Request(); dhcp_state = DHCP_REQUEST; break; case DHCP_REQUEST: if(receive_DHCP_ACK()) { dhcp_state = DHCP_ACK; save_network_params(); // 保存IP等参数 } break; case DHCP_TIMEOUT: // 超时处理：重试或切换模式 break; } } ``` ##### **3. DHCP Message Processing** ```c // 构造DHCP Discover报文 void send_DHCP_Discover() { uint8_t dhcp_pkt[576] = {0}; dhcp_pkt[0] = 1; // OP: BOOTREQUEST dhcp_pkt[1] = 1; // HTYPE: ETHERNET dhcp_pkt[2] = 6; // HLEN: 6字节MAC dhcp_pkt[3] = 0; // HOPS: 0 // 填充事务ID memcpy(&dhcp_pkt[4], &xid, 4); // 设置客户端MAC地址 memcpy(&dhcp_pkt[28], dhcp_mac, 6); // 设置选项字段 dhcp_pkt[53] = 53; // DHCP消息类型 dhcp_pkt[54] = 1; // 消息类型长度 dhcp_pkt[55] = 1; // DHCP_DISCOVER send_udp_packet(DHCP_SERVER_PORT, dhcp_pkt, 576); } // 解析DHCP Offer报文 void parse_dhcp_offer(uint8_t *pkt) { // 提取服务器IP server_ip[0] = pkt[16]; server_ip[1] = pkt[17]; server_ip[2] = pkt[18]; server_ip[3] = pkt[19]; // 提取分配IP assigned_ip[0] = pkt[16+2+16]; // yiaddr字段 assigned_ip[1] = pkt[16+2+17]; assigned_ip[2] = pkt[16+2+18]; assigned_ip[3] = pkt[16+2+19]; } ``` --- #### **III. Configuration Parameters** ##### **1. DHCP timeout settings** ```c #define DHCP_TIMEOUT_MS 10000 // 总超时时间 #define DHCP_RETRY_INTERVAL 2000 // 重试间隔 volatile uint32_t dhcp_timer = 0; void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) { if(htim->Instance == TIM3) { dhcp_timer += 100; if(dhcp_timer >= DHCP_TIMEOUT_MS) { dhcp_state = DHCP_TIMEOUT; dhcp_timer = 0; } } } ``` ##### **2. Saving network parameters** ```c uint8_t assigned_ip[4] = {0}; uint8_t subnet_mask[4] = {255,255,255,0}; uint8_t gateway_ip[4] = {192,168,1,1}; void save_network_params() { // 从DHCP ACK报文提取参数 memcpy(assigned_ip, &ack_pkt[16+2+16], 4); // yiaddr memcpy(subnet_mask, &ack_pkt[16+2+1], 4); // subnet_mask memcpy(gateway_ip, &ack_pkt[16+2+2], 4); // routers } ``` --- #### **IV. Debugging and Verification** ##### **1. Packet capture example using a logic analyzer** ```c Time | 操作类型 | 关键字段 --------------------------------------- 0.00s | DHCP Discover | MAC:00:08:DC:12:34:56 0.52s | DHCP Offer | ServerIP:192.168.1.254 0.85s | DHCP Request | RequestIP:192.168.1.100 1.20s | DHCP ACK | LeaseTime:86400s ``` ##### **2. Troubleshooting Common Problems** | **Phenomenon** | **Solution** | | --- | --- | | No DHCP response | Check MAC address uniqueness to confirm network connectivity. | | IP address conflict | Restart the device or contact your network administrator. | | Lease duration abnormal | Check DHCP server configuration | --- #### **V. Implementation of Extended Functions** ##### **1. Static IP Switching** ```c void set_static_ip() { setNETINFO(NETINFO_STATIC); setIPADDR(192,168,1,100); // 设置静态IP setGATEWAY(192,168,1,1); // 设置网关 setSUBNET(255,255,255,0); // 设置子网掩码 } ``` ##### **2. Supports multiple network cards** ```c // 配置多个W5500芯片 void multi_w5500_init() { for(int i=0; i