LwIP是Light Weight (轻型)IP协议，有无操作系统的支持都可以运行。LwIP实现的重点是在保持TCP协议主要功能的基础上减少对RAM 的占用，它只需十几KB的RAM和40K左右的ROM就可以运行，这使LwIP协议栈适合在低端的
嵌入式系统
中使用。
关于以太网的相关信息这里不做详细介绍，我只介绍如何通过ZYNQ实现数据的环路测试。实验目的是通过在SDK修改代码，实现将数据+1后返回的操作。
具体步骤：
一、VIVADO部分配置：创建处理器并设置
我的这里串口选的UART1的48和49。自己还需要配置一下DDR。
把PL部分的时钟和系统复位关闭，把GP0接口也关闭，到这里算是配置完成，其他默认即可。然后点击自动连接。可以验证下正确性，接下来生成output products和HDL wrapper。最终结果如下：
由于没有生成bit文件，所以接下来就在File->Export->Export Hardware时不需要导出bit文件。然后launch SDK。
二、SDK部分操作：创建UDP server工程并修改文件
file->new->application project
打开udp_perf_derver.c,然后将文件修改如下：
/*
* Copyright (C) 2017 - 2018 Xilinx, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
*/
/** Connection handle for a UDP Server session */
#include "udp_perf_server.h"
extern struct netif server_netif;
static struct udp_pcb *pcb;
static struct perf_stats server;
/* Report interval in ms */
#define REPORT_INTERVAL_TIME (INTERIM_REPORT_INTERVAL * 1000)
void print_app_header(void)
{
xil_printf("UDP server listening on port %d\r\n",
UDP_CONN_PORT);
xil_printf("On Host: Run $iperf -c %s -i %d -t 300 -u -b <bandwidth>\r\n",
inet_ntoa(server_netif.ip_addr),
INTERIM_REPORT_INTERVAL);
}
static void print_udp_conn_stats(void)
{
xil_printf("[%3d] local %s port %d connected with ",
server.client_id, inet_ntoa(server_netif.ip_addr),
UDP_CONN_PORT);
xil_printf("%s port %d\r\n", inet_ntoa(pcb->remote_ip),
pcb->remote_port);
xil_printf("[ ID] Interval\t Transfer Bandwidth\t");
xil_printf(" Lost/Total Datagrams\n\r");
}
static void stats_buffer(char* outString,
double data, enum measure_t type)
{
int conv = KCONV_UNIT;
const char *format;
double unit = 1024.0;
if (type == SPEED)
unit = 1000.0;
while (data >= unit && conv <= KCONV_GIGA) {
data /= unit;
conv++;
}
/* Fit data in 4 places */
if (data < 9.995) { /* 9.995 rounded to 10.0 */
format = "%4.2f %c"; /* #.## */
} else if (data < 99.95) { /* 99.95 rounded to 100 */
format = "%4.1f %c"; /* ##.# */
} else {
format = "%4.0f %c"; /* #### */
}
sprintf(outString, format, data, kLabel[conv]);
}
/** The report function of a TCP server session */
static void udp_conn_report(u64_t diff,
enum report_type report_type)
{
u64_t total_len, cnt_datagrams, cnt_dropped_datagrams, total_packets;
u32_t cnt_out_of_order_datagrams;
double duration, bandwidth = 0;
char data[16], perf[16], time[64], drop[64];
if (report_type == INTER_REPORT) {
total_len = server.i_report.total_bytes;
cnt_datagrams = server.i_report.cnt_datagrams;
cnt_dropped_datagrams = server.i_report.cnt_dropped_datagrams;
} else {
server.i_report.last_report_time = 0;
total_len = server.total_bytes;
cnt_datagrams = server.cnt_datagrams;
cnt_dropped_datagrams = server.cnt_dropped_datagrams;
cnt_out_of_order_datagrams = server.cnt_out_of_order_datagrams;
}
total_packets = cnt_datagrams + cnt_dropped_datagrams;
/* Converting duration from milliseconds to secs,
* and bandwidth to bits/sec .
*/
duration = diff / 1000.0; /* secs */
if (duration)
bandwidth = (total_len / duration) * 8.0;
stats_buffer(data, total_len, BYTES);
stats_buffer(perf, bandwidth, SPEED);
/* On 32-bit platforms, xil_printf is not able to print
* u64_t values, so converting these values in strings and
* displaying results
*/
sprintf(time, "%4.1f-%4.1f sec",
(double)server.i_report.last_report_time,
(double)(server.i_report.last_report_time + duration));
sprintf(drop, "%4llu/%5llu (%.2g%%)", cnt_dropped_datagrams,
total_packets,
(100.0 * cnt_dropped_datagrams)/total_packets);
xil_printf("[%3d] %s %sBytes %sbits/sec %s\n\r", server.client_id,
time, data, perf, drop);
if (report_type == INTER_REPORT) {
server.i_report.last_report_time += duration;
} else if ((report_type != INTER_REPORT) && cnt_out_of_order_datagrams) {
xil_printf("[%3d] %s %u datagrams received out-of-order\n\r",
server.client_id, time,
cnt_out_of_order_datagrams);
}
}
static void reset_stats(void)
{
server.client_id++;
/* Save start time */
server.start_time = get_time_ms();
server.end_time = 0; /* ms */
server.total_bytes = 0;
server.cnt_datagrams = 0;
server.cnt_dropped_datagrams = 0;
server.cnt_out_of_order_datagrams = 0;
server.expected_datagram_id = 0;
/* Initialize Interim report paramters */
server.i_report.start_time = 0;
server.i_report.total_bytes = 0;
server.i_report.cnt_datagrams = 0;
server.i_report.cnt_dropped_datagrams = 0;
server.i_report.last_report_time = 0;
}
//主要修改代码部分：新定义了一个数组用来存放接受的数据
#define MAX_FLASH_LEN 16*1024*1024
unsigned long total_bytes = 0;
unsigned char rxbuffer[MAX_FLASH_LEN];
/** Receive data on a udp session */
static void udp_recv_perf_traffic(void *arg, struct udp_pcb *tpcb,
struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
static u8_t first = 1;
u32_t drop_datagrams = 0;
s32_t recv_id;
int i = 0;
//下面为核心修改处
while (p->tot_len != p->len) {
memcpy(&rxbuffer[total_bytes], p->payload, p->len);
total_bytes += p->len;
p = p->next;
}
memcpy(&rxbuffer[total_bytes], p->payload, p->len);
total_bytes = p->len;
for(int i=0;i<total_bytes;i++)
{
rxbuffer[i]++;
p->payload = &rxbuffer[i];
p->tot_len = 1;
udp_sendto(tpcb,p,addr,port);
}//修改结束
/* first, check if the datagram is received in order */
#ifdef __MICROBLAZE__
/* For Microblaze, word access are at 32 bit boundaries.
* To read complete 4 byte of UDP ID from data payload,
* we should read upper 2 bytes from current word boundary
* of payload and lower 2 bytes from next word boundary of
* payload.
*/
s16_t *payload;
payload = (s16_t *) (p->payload);
recv_id = (ntohs(payload[0]) << 16) | ntohs(payload[1]);
#else
recv_id = ntohl(*((int *)(p->payload)));
#endif
if (first && (recv_id == 0)) {
/* First packet should always start with recv id 0.
* However, If Iperf client is running with parallel
* thread, then this condition will also avoid
* multiple print of connection header
*/
pcb->remote_ip = *addr;
pcb->remote_port = port;
reset_stats();
/* Print connection statistics */
print_udp_conn_stats();
first = 0;
} else if (first) {
/* Avoid rest of the packets if client
* connection is already terminated.
*/
return;
}
if (recv_id < 0) {
u64_t now = get_time_ms();
u64_t diff_ms = now - server.start_time;
/* Send Ack */
udp_sendto(tpcb, p, addr, port);
udp_conn_report(diff_ms, UDP_DONE_SERVER);
xil_printf("UDP test passed Successfully\n\r");
first = 1;
pbuf_free(p);
return;
}
/* Update dropped datagrams statistics */
if (server.expected_datagram_id != recv_id) {
if (server.expected_datagram_id < recv_id) {
drop_datagrams =
recv_id - server.expected_datagram_id;
server.cnt_dropped_datagrams += drop_datagrams;
server.expected_datagram_id = recv_id + 1;
} else if (server.expected_datagram_id > recv_id) {
server.cnt_out_of_order_datagrams++;
}
} else {
server.expected_datagram_id++;
}
server.cnt_datagrams++;
/* Record total bytes for final report */
server.total_bytes += p->tot_len;
if (REPORT_INTERVAL_TIME) {
u64_t now = get_time_ms();
server.i_report.cnt_datagrams++;
server.i_report.cnt_dropped_datagrams += drop_datagrams;
/* Record total bytes for interim report */
server.i_report.total_bytes += p->tot_len;
if (server.i_report.start_time) {
u64_t diff_ms = now - server.i_report.start_time;
if (diff_ms >= REPORT_INTERVAL_TIME) {
udp_conn_report(diff_ms, INTER_REPORT);
/* Reset Interim report counters */
server.i_report.start_time = 0;
server.i_report.total_bytes = 0;
server.i_report.cnt_datagrams = 0;
server.i_report.cnt_dropped_datagrams = 0;
}
} else {
/* Save start time for interim report */
server.i_report.start_time = now;
}
}
pbuf_free(p);
return;
}
void start_application(void)
{
err_t err;
/* Create Server PCB */
pcb = udp_new();
if (!pcb) {
xil_printf("UDP server: Error creating PCB. Out of Memory\r\n");
return;
}
err = udp_bind(pcb, IP_ADDR_ANY, UDP_CONN_PORT);
if (err != ERR_OK) {
xil_printf("UDP server: Unable to bind to port");
xil_printf(" %d: err = %d\r\n", UDP_CONN_PORT, err);
udp_remove(pcb);
return;
}
/* specify callback to use for incoming connections */
udp_recv(pcb, udp_recv_perf_traffic, NULL);
return;
}
这部分代码实现的功能是将接受到的数据拷贝到另一块内存中，然后对数据进行加一操作，再通过建立工程后自动定义的UDP回传函数将加一后的数据传回去。
三：测试
首先需要设置网口，在控制面板里设置如下：
在以太网的属性中将IPV4设置如下：保证电脑IP与ZYNQ网口IP在一个网段。
然后开始测试：连接好串口后，SDK会打印如下信息，代表网口连接成功
然后再网口助手中设置一下端口信息：
发送0 1 2 3 4后，返回数据如下：可以看到预设的功能以实现。
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