lwip pppos 例程

以下是使用lwIP库中的pppos协议栈的简单例程：

#include "lwip/opt.h"
#include "lwip/sys.h"
#include "lwip/api.h"
#include "lwip/ppp.h"
#include "lwip/sio.h"
#include "lwip/tcpip.h"

#define PPP_TTY_OUTQLEN 256
#define PPP_TTY_INQLEN  256

static struct netif pppos_netif;
static u8_t ppp_output_buf[PPP_MRU + PPP_HDRLEN];
static u8_t ppp_input_buf[PPP_MRU + PPP_HDRLEN];

static void ppp_link_status_cb(void *ctx, int err_code, void *arg)
{
    if (err_code == PPPERR_NONE) {
        printf("ppp_link_status_cb: Connected\n");
    } else {
        printf("ppp_link_status_cb: Disconnected. err_code = %d\n", err_code);
    }
}

static err_t ppp_output_cb(ppp_pcb *pcb, u8_t *data, int len, void *ctx)
{
    sio_write(&pppos_netif, data, len);
    return ERR_OK;
}

static void pppos_thread(void *arg)
{
    ppp_pcb *ppp;
    u32_t i;

    /* Set up PPP control block */
    ppp = ppp_new();
    ppp_set_auth(ppp, PPPAUTHTYPE_NONE, "username", "password");
    ppp_set_default(ppp);

    ppp_set_link_status_callback(ppp, ppp_link_status_cb, NULL);

    /* Set up PPP over serial I/O */
    pppos_init(ppp);

    /* Open the serial port */
    if (sio_open() != SIO_OK) {
        printf("Failed to open serial port\n");
        return;
    }

    /* Initialise the netif struct */
    netif_add(&pppos_netif, ip4_addr_unspecified(), ip4_addr_unspecified(),
              ip4_addr_unspecified(), NULL, pppos_init, tcpip_input);

    netif_set_default(&pppos_netif);
    netif_set_link_up(&pppos_netif);

    /* Start PPP connection */
    ppp_connect(ppp, 0);

    while (1) {
        /* Wait for incoming data */
        i = sio_read(&pppos_netif, ppp_input_buf, PPP_TTY_INQLEN);

        if (i > 0) {
            pppos_input_tcpip(ppp, ppp_input_buf, i);
        }

        /* Send outgoing data */
        if (ppp_output_waiting(ppp)) {
            i = ppp_output(ppp, ppp_output_buf, PPP_TTY_OUTQLEN);

            if (i > 0) {
                sio_write(&pppos_netif, ppp_output_buf, i);
            }
        }

        /* Sleep for 100ms */
        sys_msleep(100);
    }
}

int main()
{
    sys_init();

    tcpip_init(NULL, NULL);

    sys_thread_new("pppos", pppos_thread, NULL, DEFAULT_THREAD_STACKSIZE, DEFAULT_THREAD_PRIO);

    while (1) {
        sys_msleep(1000);
    }

    return 0;
}

这个例程使用了串口进行物理层的通信，将串口数据传递给ppp协议栈进行处理，通过回调函数处理ppp连接状态和ppp输出数据，最终将ppp输出数据通过串口发送出去。需要注意的是，ppp协议栈的输入和输出缓冲区大小需要根据实际应用进行调整。