simple data transfer with microblaze and lwip

Question

So I cant find in the internet any simple example than echo program for microblaze and lwip which is working fine for me and here are thier files : echo.c :

/*
 * Copyright (c) 2009 Xilinx, Inc.  All rights reserved.
 *
 * Xilinx, Inc.
 * XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A
 * COURTESY TO YOU.  BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS
 * ONE POSSIBLE   IMPLEMENTATION OF THIS FEATURE, APPLICATION OR
 * STANDARD, XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION
 * IS FREE FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE
 * FOR OBTAINING ANY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION.
 * XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO
 * THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO
 * ANY WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE
 * FROM CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

#include <stdio.h>
#include <string.h>

#include "lwip/err.h"
#include "lwip/tcp.h"


int transfer_data() {
    return 0;
}

void print_app_header()
{
    xil_printf("\n\r\n\r-----lwIP TCP echo server ------\n\r");
    xil_printf("TCP packets sent to port 6001 will be echoed back\n\r");
}

err_t recv_callback(void *arg, struct tcp_pcb *tpcb,
                               struct pbuf *p, err_t err)
{
    /* do not read the packet if we are not in ESTABLISHED state */
    if (!p) {
        tcp_close(tpcb);
        tcp_recv(tpcb, NULL);
        return ERR_OK;
    }

    /* indicate that the packet has been received */
    tcp_recved(tpcb, p->len);

    /* echo back the payload */
    /* in this case, we assume that the payload is < TCP_SND_BUF */
    if (tcp_sndbuf(tpcb) > p->len) {
        err = tcp_write(tpcb, p->payload, p->len, 1);
    } else
        print("no space in tcp_sndbuf\n\r");

    /* free the received pbuf */
    pbuf_free(p);

    return ERR_OK;
}

err_t accept_callback(void *arg, struct tcp_pcb *newpcb, err_t err)
{
    static int connection = 1;

    /* set the receive callback for this connection */
    tcp_recv(newpcb, recv_callback);

    /* just use an integer number indicating the connection id as the
       callback argument */
    tcp_arg(newpcb, (void*)connection);

    /* increment for subsequent accepted connections */
    connection++;

    return ERR_OK;
}


int start_application()
{
    struct tcp_pcb *pcb;
    err_t err;
    unsigned port = 7;

    /* create new TCP PCB structure */
    pcb = tcp_new();
    if (!pcb) {
        xil_printf("Error creating PCB. Out of Memory\n\r");
        return -1;
    }

    /* bind to specified @port */
    err = tcp_bind(pcb, IP_ADDR_ANY, port);
    if (err != ERR_OK) {
        xil_printf("Unable to bind to port %d: err = %d\n\r", port, err);
        return -2;
    }

    /* we do not need any arguments to callback functions */
    tcp_arg(pcb, NULL);

    /* listen for connections */
    pcb = tcp_listen(pcb);
    if (!pcb) {
        xil_printf("Out of memory while tcp_listen\n\r");
        return -3;
    }

    /* specify callback to use for incoming connections */
    tcp_accept(pcb, accept_callback);

    xil_printf("TCP echo server started @ port %d\n\r", port);

    return 0;
}

and here is main.c :

/*
 * Copyright (c) 2009-2010 Xilinx, Inc.  All rights reserved.
 *
 * Xilinx, Inc.
 * XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A
 * COURTESY TO YOU.  BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS
 * ONE POSSIBLE   IMPLEMENTATION OF THIS FEATURE, APPLICATION OR
 * STANDARD, XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION
 * IS FREE FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE
 * FOR OBTAINING ANY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION.
 * XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO
 * THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO
 * ANY WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE
 * FROM CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

#include <stdio.h>

#include "xparameters.h"

#include "netif/xadapter.h"

#include "platform.h"
#include "platform_config.h"

/* defined by each RAW mode application */
void print_app_header();
int start_application();
int transfer_data();

/* missing declaration in lwIP */
void lwip_init();

void
print_ip(char *msg, struct ip_addr *ip) 
{
    print(msg);
    xil_printf("%d.%d.%d.%d\n\r", ip4_addr1(ip), ip4_addr2(ip), 
            ip4_addr3(ip), ip4_addr4(ip));
}

void
print_ip_settings(struct ip_addr *ip, struct ip_addr *mask, struct ip_addr *gw)
{

    print_ip("Board IP: ", ip);
    print_ip("Netmask : ", mask);
    print_ip("Gateway : ", gw);
}

int main()
{
    struct netif *netif, server_netif;
    struct ip_addr ipaddr, netmask, gw;

    /* the mac address of the board. this should be unique per board */
    unsigned char mac_ethernet_address[] = { 0x00, 0x0a, 0x35, 0x00, 0x01, 0x02 };

    netif = &server_netif;

    init_platform();

    /* initliaze IP addresses to be used */
    IP4_ADDR(&ipaddr,  192, 168,   1, 10);
    IP4_ADDR(&netmask, 255, 255, 255,  0);
    IP4_ADDR(&gw,      192, 168,   1,  1);

    print_app_header();
    print_ip_settings(&ipaddr, &netmask, &gw);

    lwip_init();

    /* Add network interface to the netif_list, and set it as default */
    if (!xemac_add(netif, &ipaddr, &netmask, &gw, mac_ethernet_address, PLATFORM_EMAC_BASEADDR)) {
        xil_printf("Error adding N/W interface\n\r");
        return -1;
    }
    netif_set_default(netif);

    /* Create a new DHCP client for this interface.
     * Note: you must call dhcp_fine_tmr() and dhcp_coarse_tmr() at
     * the predefined regular intervals after starting the client.
     */
    /* dhcp_start(netif); */

    /* now enable interrupts */
    platform_enable_interrupts();

    /* specify that the network if is up */
    netif_set_up(netif);

    /* start the application (web server, rxtest, txtest, etc..) */
    start_application();

    /* receive and process packets */
    while (1) {
        xemacif_input(netif);
        tcp_write()
        //transfer_data();
    }

    /* never reached */
    cleanup_platform();

    return 0;
}

Now i cant understand this code at all ( some of it but not all of it) can you guys tell me for a start how to change this code so instead of echoing back the same data , that it sends back to the host a string conatining "hey" . And thank you.

Answer 1

this line

 err = tcp_write(tpcb, p->payload, p->len, 1);

send back data from rescive data p (p->payload - incoming message) change it, like

err = tcp_write(tpcb, "hey", 3, 1);