stm32 modbus tcp程序实例

以下是一个基于STM32Cube HAL库的Modbus TCP程序实例：

#include "main.h"
#include "lwip.h"
#include "lwip/api.h"
#include "lwip/tcp.h"
#include "mbtcp.h"

void modbus_tcp_task(void *arg)
{
  struct netconn *conn, *newconn;
  struct netbuf *buf;
  uint8_t recv_data[MBTCP_MAX_PDU_LEN];
  uint16_t len, pdu_len, err;

  /* Create a new connection identifier. */
  conn = netconn_new(NETCONN_TCP);
  if (conn != NULL) {
    /* Bind to port 502 */
    netconn_bind(conn, NULL, MBTCP_PORT);
    /* Put the connection into LISTEN state. */
    netconn_listen(conn);

    while (1) {
      /* Wait for a new connection. */
      err = netconn_accept(conn, &newconn);
      if (err == ERR_OK) {
        while ((err = netconn_recv(newconn, &buf)) == ERR_OK) {
          /* Process Modbus TCP PDU */
          netbuf_copy(buf, recv_data, netbuf_len(buf));
          pdu_len = mbtcp_process_pdu(recv_data, netbuf_len(buf));

          /* Send response */
          if (pdu_len > 0) {
            err = netconn_write(newconn, recv_data, pdu_len, NETCONN_COPY);
          }

          /* Deallocate memory */
          netbuf_delete(buf);
        }
        /* Close connection */
        netconn_close(newconn);
        /* Delete connection */
        netconn_delete(newconn);
      }
    }
  }
}

int main(void)
{
  /* Initialize lwIP stack */
  MX_LWIP_Init();

  /* Initialize Modbus TCP */
  mbtcp_init();

  /* Create Modbus TCP task */
  osThreadDef(modbus_tcp, modbus_tcp_task, osPriorityNormal, 0, configMINIMAL_STACK_SIZE * 2);
  osThreadCreate(osThread(modbus_tcp), NULL);

  while (1) {

  }
}

上述代码使用lwIP网络栈实现了一个Modbus TCP服务器，并使用了一个名为`mbtcp_process_pdu()`的函数来处理Modbus TCP PDU。具体实现和`mbtcp_init()`函数实现可以参考Modbus TCP库的文档。