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lwIP is a popular free TCP/IP stack for many embedded processors. The following workshop enables DHCP client so that it can acquire an IP from a DHCP server.

Here we pick a real piece of hardware from Atmel:  EVK1100. Its processor is 32UC3A0512, but the codes below should work in other hardware.

Software Development Platform: AVR32 with lwIP and FreeRTOS.

To enable a DHCP client on EVK1100, using lwIP on FreeRTOS, under AVR32

1. AVR32->File->New->Example, select EVK1100-SERVICES-LWIP example
2. Give a Project Name: MyTestFromLwIP, then click Finish. This will create a new project under the Project Explorer pane.
3. Open MyTestFromLwIP->src->CONFIG->lwipopts.h, and change
   
         #define LWIP_DHCP 0
                   to
         #define LWIP_DHCP 1
   
         #define MEMP_NUM_UDP_PCB 1
                   to
         #define MEMP_NUM_UDP_PCB 2
   
   
4. Add #include "lwip/dhcp.h" to the header section of MyTestFromLwIP->src->NETWORK->ethernet.c
5. Open MyTestFromLwIP->src->NETWORK->ethernet.c, and replace prvEthernetConfigureInterface with:
   
         static void prvEthernetConfigureInterface(void * param){
         struct ip_addr xIpAddr, xNetMask, xGateway;
         extern err_t ethernetif_init( struct netif *netif );
         unsigned portCHAR MacAddress[6];
   
         MacAddress[0] = ETHERNET_CONF_ETHADDR0;
         MacAddress[1] = ETHERNET_CONF_ETHADDR1;
         MacAddress[2] = ETHERNET_CONF_ETHADDR2;
         MacAddress[3] = ETHERNET_CONF_ETHADDR3;
         MacAddress[4] = ETHERNET_CONF_ETHADDR4;
         MacAddress[5] = ETHERNET_CONF_ETHADDR5;
   
         vMACBSetMACAddress( MacAddress );
   
         IP4_ADDR( &xIpAddr,0,0,0,0 );
         IP4_ADDR( &xNetMask,0,0,0,0 );
         IP4_ADDR( &xGateway,0,0,0,0 );
   
         netif_add( &MACB_if, &xIpAddr, &xNetMask, &xGateway, NULL, ethernetif_init, tcpip_input );
         netif_set_default( &MACB_if );
   
         dhcp_start(&MACB_if);
         }
   
6. Add the following codes to module portTASK_FUNCTION( vStartEthernetTask, pvParameters ), after prvlwIPInit():
   
        //init_dbg_rs232(FOSC0);
        int mscnt =0;
    
         while (MACB_if.ip_addr.addr==0) {
                 sys_msleep(DHCP_FINE_TIMER_MSECS);
                 dhcp_fine_tmr();
                 mscnt += DHCP_FINE_TIMER_MSECS;
                 if (mscnt >= DHCP_COARSE_TIMER_SECS*1000) {
                        dhcp_coarse_tmr();
                        mscnt = 0;
                 }
          }
   
          //print_dbg("\nDone with DHCP");
          //print_dbg("\nAcquired IP =");
          // print_dbg_ulong(0xff&(MACB_if.ip_addr.addr>>24));
          //print_dbg(".");
          //print_dbg_ulong(0xff&(MACB_if.ip_addr.addr>>16));
          //print_dbg(".");
          //print_dbg_ulong(0xff&(MACB_if.ip_addr.addr>>8));
          //print_dbg(".");
          //print_dbg_ulong(0xff&(MACB_if.ip_addr.addr));
   
   
7. To use the debug outputs, you will need uncomment all the functions in the codes and add  #include "print_funcs.h"  to the header section of ethernet.c. To receive the debug outputs, connect a RS232 cable to UART 1 of EVK1100, start Windows' HyperTerminal and set Bits per second =115200, Data bits = 8, Parity = none, Stop bits = 1, Flow control = None.
8. Build and run it in a network with a DHCP server, such as a DSL router, and you can ping the IP once it is acquired from a DHCP server.