tls_os_timer_create(&mqtt.mqtt_demo_heartbeat_timer,
                    mqtt_demo_heart_timer,
                    NULL, 50, TRUE, (u8 *)"mqtt loop");
                    
        下面是源代码
        tls_os_timer_start(mqtt.mqtt_demo_heartbeat_timer);
        
        sprintf(str,"{\"current_temperature\":%.2f,\"current_humidity\":%.2f}",Temperature,Humidity);
        app_mqtt_publish("data_report",str);
        
        tls_os_time_delay(3000);
        
        app_mqtt_disconnect(&mqtt);        //断开连接
        
        tls_os_timer_stop(mqtt.mqtt_demo_heartbeat_timer);
        wm_printf("close mqtt_demo_loop\n");