串口发送一段时间后停止发送

#include <SHT85.h>
#include <rtthread.h>
#include <rtdevice.h>
#include <board.h>
#include "sht3x.h"
#include <Usart.h>
#include <stdio.h>
#define SHT85_I2C_BUS_NAME        "i2c1"
#define SHT85_ADDR                 0x44
#define THREAD_PRIORITY         25
#define THREAD_STACK_SIZE       1024
#define THREAD_TIMESLICE        5
static rt_thread_t Sht85_Thread = RT_NULL;
static rt_thread_t Sht85_Print_Thread = RT_NULL;
static rt_sem_t Sht85_sem = RT_NULL;
float humidity = 0;
void SHT85_Init(void)
{
    Sht85_sem = rt_sem_create("SHT85_sem", 0, RT_IPC_FLAG_FIFO);
    //i2c1采集线程初始化 //
    Sht85_Thread = rt_thread_create("SHT85_Get", SHT85_Thread_entry, RT_NULL, THREAD_STACK_SIZE, THREAD_PRIORITY, THREAD_TIMESLICE);
    if(Sht85_Thread!=RT_NULL)
    {
        rt_thread_startup(Sht85_Thread);
    }
    else {
        rt_kprintf("sht85 thread create failed\n");
    }
    Sht85_Print_Thread = rt_thread_create("SHT85_Print",SHT85_Print_Thread_entry,RT_NULL,THREAD_STACK_SIZE,THREAD_PRIORITY-1,THREAD_TIMESLICE);
    if(Sht85_Print_Thread!=RT_NULL)
    {
        rt_thread_startup(Sht85_Print_Thread);
    }
}
static void SHT85_Thread_entry(void* parameter)
{
    sht3x_device_t sht85_device;
    sht85_device = sht3x_init(SHT85_I2C_BUS_NAME, SHT85_ADDR);
    int i = 0;
    while(1)
    {
        if(sht3x_read_singleshot(sht85_device)==RT_EOK)
        {
            humidity = sht85_device->humidity;
            I2c1_Buffer[i++] = humidity;
            if(i==10)
            {
                rt_sem_release(Sht85_sem);
                i = 0;
            }
        }
        else {
            rt_kprintf("read sht85 fail.\r\n");
            break;
        }
        rt_thread_mdelay(200);
    }
}
static void SHT85_Print_Thread_entry(void* parameter)
{
    static rt_err_t sem_result;
    while(1)
    {
        sem_result = rt_sem_take(Sht85_sem, RT_WAITING_FOREVER);
        if(sem_result==RT_EOK)
        {
            printf("i2c1 value: %.2f\n",I2c1_Buffer[0]);
            uart6_transmit(I2c1_Buffer[0],0x02);
        }
        else {
            rt_sem_delete(Sht85_sem);
            return;
        }
        rt_thread_mdelay(2000);
    }
}

#include <rtthread.h>
#include <Usart.h>
#include <rtdevice.h>
#include <math.h>
#define UART_NAME       "uart6"       /* 需要操作的设备 */
static rt_device_t serial;                   /* 设备句柄 */
struct serial_configure config = RT_SERIAL_CONFIG_DEFAULT;
void uart6_transmit(float x,uint8_t func)            /*x为需要显示的变量（湿度、风速等），function为显示功能参数 */                                                   //
{                                                     //0x01--温度、0x02--湿度、0x03--风速、0x04--等效温度
    rt_err_t ret = RT_EOK;
    rt_size_t send_len = 0;
    uint8_t PN;                                          //正负位//
    uint8_t digits;                                      //小数点位//
    Data_TypeDef num;
    num.Frame_Head = 0xAA;
    num.Length = 5;
    num.Function = func;
    if(x<0)
    {
        PN = 0;
    }
    else {
        PN = 1;
    }
    if(x>=10 || (x<=-1&&x>-10))                                                //显示一位小数//
    {
        digits = 1;
        if(x>0)
        {
            x = x*10;
        }
        else {
            x = -x*10;
        }
    }
    else if(x>-1 && x<10)                                                     //显示两位小数//
    {
        digits = 2;
        if(x>0)
        {
            x = x*100;
        }
        else {
            x = -x*100;
        }
    }
    else if(x<=-10)                                                             //显示零位小数//
    {
        digits = 0;
        x = -x;
    }
    num.Data_Nature = digits + PN*16;
    num.Data_High = (int)x>>8;              //数据化为十六进制高八位//
    num.Data_Low = (int)x & (0xFF);         //数据化为十六进制低八位//
    num.BBC = num.Function^num.Data_High^num.Data_Low^num.Data_Nature;
    uint8_t str[7] = {num.Frame_Head,num.Length,num.Function,num.Data_High,num.Data_Low,num.Data_Nature,num.BBC};
    /* 查找系统中的串口设备 */
    serial = rt_device_find(UART_NAME);
    if (!serial)
    {
        rt_kprintf("find %s failed!\n",UART_NAME);
    }
    /*配置参数*/
    config.baud_rate = BAUD_RATE_9600;        //修改波特率为 9600
    config.data_bits = DATA_BITS_8;           //数据位 8
    config.stop_bits = STOP_BITS_1;           //停止位 1
    config.bufsz     = 256;                   //修改缓冲区 buff size
    config.parity    = PARITY_NONE;           //无奇偶校验位
    rt_device_control(serial, RT_DEVICE_CTRL_CONFIG, &config);
    /* 以中断接收及轮询发送模式打开串口设备 */
    ret = rt_device_open(serial, RT_DEVICE_FLAG_INT_RX);
    if (ret != RT_EOK)
    {
        rt_kprintf("open device failed\r\n");
    }
    /* 发送字符串 */
    send_len = rt_device_write(serial, 0, str, sizeof(str));
    if (send_len != sizeof(str))
    {
        rt_kprintf("send data failed\r\n");
    }
///*     关闭设备   */
//    ret = rt_device_close(serial);
//    if (ret != RT_EOK)
//    {
//        rt_kprintf("close device failed\r\n");
//    }
//
////    rt_kprintf("serial device test successful\r\n");
}