STM32F103固件库建立tcp客户端，在建立数据接收回调函数时将数据一个一个写入环形缓冲区，并在主函数从缓冲区读出数据，并发送出去，代码

以下是一个简单的示例代码，用于建立TCP客户端并将数据写入环形缓冲区：

#include "stm32f10x.h"
#include "lwip/opt.h"
#include "lwip/arch.h"
#include "lwip/api.h"

#define TCP_CLIENT_BUFFER_SIZE 1024

static char tcp_client_buffer[TCP_CLIENT_BUFFER_SIZE];
static u16_t tcp_client_write_index = 0;
static u16_t tcp_client_read_index = 0;
static struct netconn *tcp_client_conn = NULL;

void tcp_client_data_receive_callback(void *arg, struct netconn *conn, enum netconn_evt evt, u16_t len)
{
    if (evt == NETCONN_EVT_RCVMINUS) {
        return;
    }
    
    char *recv_buf = malloc(len);
    if (recv_buf == NULL) {
        return;
    }
    
    struct netbuf *recv_netbuf = NULL;
    if (netconn_recv(conn, &recv_netbuf) == ERR_OK) {
        void *data;
        u16_t recv_len;
        while (netbuf_data(recv_netbuf, &data, &recv_len) == ERR_OK) {
            memcpy(recv_buf, data, recv_len);
            recv_buf += recv_len;
        }
        netbuf_delete(recv_netbuf);
        
        // write received data to circular buffer
        for (u16_t i = 0; i < len; i++) {
            tcp_client_buffer[tcp_client_write_index] = *(recv_buf - len + i);
            tcp_client_write_index = (tcp_client_write_index + 1) % TCP_CLIENT_BUFFER_SIZE;
        }
    }
    
    free(recv_buf);
}

void tcp_client_send_data(void)
{
    if (tcp_client_conn == NULL) {
        return;
    }
    
    while (tcp_client_write_index != tcp_client_read_index) {
        u16_t send_len = (tcp_client_write_index > tcp_client_read_index) ?
                         (tcp_client_write_index - tcp_client_read_index) :
                         (TCP_CLIENT_BUFFER_SIZE - tcp_client_read_index);
        
        struct netbuf *send_netbuf = netbuf_new();
        if (send_netbuf == NULL) {
            return;
        }
        
        char *send_buf = malloc(send_len);
        if (send_buf == NULL) {
            netbuf_delete(send_netbuf);
            return;
        }
        
        // read data from circular buffer
        for (u16_t i = 0; i < send_len; i++) {
            *(send_buf + i) = tcp_client_buffer[tcp_client_read_index];
            tcp_client_read_index = (tcp_client_read_index + 1) % TCP_CLIENT_BUFFER_SIZE;
        }
        
        netbuf_ref(send_netbuf, send_buf, send_len);
        if (netconn_send(tcp_client_conn, send_netbuf) != ERR_OK) {
            netbuf_delete(send_netbuf);
            free(send_buf);
            return;
        }
        
        netbuf_delete(send_netbuf);
        free(send_buf);
    }
}

void tcp_client_init(void)
{
    tcp_client_conn = netconn_new(NETCONN_TCP);
    if (tcp_client_conn == NULL) {
        return;
    }
    
    ip_addr_t server_ipaddr;
    IP4_ADDR(&server_ipaddr, 192, 168, 1, 100);
    err_t err = netconn_connect(tcp_client_conn, &server_ipaddr, 5000);
    if (err != ERR_OK) {
        netconn_delete(tcp_client_conn);
        tcp_client_conn = NULL;
        return;
    }
    
    netconn_set_recvtimeout(tcp_client_conn, 10);
    netconn_set_nonblocking(tcp_client_conn, 1);
    netconn_set_recv_callback(tcp_client_conn, tcp_client_data_receive_callback);
}

int main(void)
{
    tcp_client_init();
    
    while (1) {
        tcp_client_send_data();
        // do other things
    }
    
    return 0;
}

这个示例代码中使用了lwIP协议栈，通过netconn API建立TCP客户端连接，并在数据接收回调函数中将接收到的数据写入环形缓冲区。发送数据时，从环形缓冲区读取数据并发送到服务器。注意，这个示例代码只是一个简单的演示，仅供参考，具体实现需要根据你的具体需求进行修改。