diff --git a/DSView/pv/sigsession.cpp b/DSView/pv/sigsession.cpp
index c2935bb9..6fa66933 100644
--- a/DSView/pv/sigsession.cpp
+++ b/DSView/pv/sigsession.cpp
@@ -218,10 +218,8 @@ namespace pv
         ds_device_handle old_dev = _device_agent.handle();
  
         _callback->trigger_message(DSV_MSG_CURRENT_DEVICE_CHANGE_PREV);
-
         // Release the old device.
         _device_agent.release();
-
         _device_status = ST_INIT;
 
         if (ds_active_device(dev_handle) != SR_OK)
@@ -231,7 +229,6 @@ namespace pv
         }
 
         _device_agent.update();
-
         set_collect_mode(COLLECT_SINGLE);
 
         if (_device_agent.is_file()){
@@ -255,16 +252,31 @@ namespace pv
         // The current device changed.
         _callback->trigger_message(DSV_MSG_CURRENT_DEVICE_CHANGED);
 
-        if (_device_agent.is_hardware() && _device_agent.check_firmware_version() == false)
+        if (ds_get_last_error() == SR_ERR_DEVICE_FIRMWARE_VERSION_LOW)
         {
-            QString strMsg = L_S(STR_PAGE_MSG, S_ID(IDS_MSG_TO_RECONNECT_FOR_FIRMWARE), "Please reconnect the device!");
+            QString strMsg = L_S(STR_PAGE_MSG, S_ID(IDS_MSG_TO_RECONNECT_FOR_FIRMWARE), 
+                    "Please reconnect the device!");
             _callback->delay_prop_msg(strMsg);
+            return false;
         }
 
-        if (_device_agent.handle() != dev_handle && old_dev != NULL_HANDLE)
+        if (ds_get_last_error() == SR_ERR_FIRMWARE_NOT_EXIST)
         {
-            QString strMsg = L_S(STR_PAGE_MSG, S_ID(IDS_MSG_DEVICE_BUSY_SWITCH_FAILED), "Device is busy!");
-            MsgBox::Show(strMsg);
+            QString strMsg = L_S(STR_PAGE_MSG, S_ID(IDS_MSG_FIRMWARE_NOT_EXIST), 
+                    "Firmware not exist!");
+            _callback->delay_prop_msg(strMsg);
+            return false;
+        }
+
+        if (ds_get_last_error() == SR_ERR_DEVICE_IS_EXCLUSIVE)
+        {
+            QString strMsg = L_S(STR_PAGE_MSG, S_ID(IDS_MSG_DEVICE_BUSY_SWITCH_FAILED), 
+                        "Device is busy!");
+            if (old_dev != NULL_HANDLE)
+                MsgBox::Show(strMsg);
+            else
+                _callback->delay_prop_msg(strMsg);
+            return false;
         }
 
         return true;
diff --git a/lang/cn/msg.json b/lang/cn/msg.json
index 310fd388..d97fe07d 100644
--- a/lang/cn/msg.json
+++ b/lang/cn/msg.json
@@ -369,5 +369,9 @@
     {
         "id": "IDS_MSG_DEVICE_SPEED_TOO_LOW",
         "text": "错误: 当前连接的USB端口速率过低(<480Mbps)!"
+    },
+    {
+        "id": "IDS_MSG_FIRMWARE_NOT_EXIST",
+        "text": "错误: 固件文件不存在!"
     }
 ]
diff --git a/lang/en/msg.json b/lang/en/msg.json
index a3ea20d7..f50fc3c0 100644
--- a/lang/en/msg.json
+++ b/lang/en/msg.json
@@ -370,5 +370,9 @@
     {
         "id": "IDS_MSG_DEVICE_SPEED_TOO_LOW",
         "text": "Error: USB port speed is too low (<480Mbps)!"
+    },
+    {
+        "id": "IDS_MSG_FIRMWARE_NOT_EXIST",
+        "text": "Error: Firmware file is not exist!"
     }
 ]
diff --git a/libsigrok4DSL/error.c b/libsigrok4DSL/error.c
index df3e60f8..64272163 100644
--- a/libsigrok4DSL/error.c
+++ b/libsigrok4DSL/error.c
@@ -81,7 +81,7 @@ SR_API const char *sr_error_str(int error_code)
 	case SR_ERR_NA:
 		str = "not applicable";
 		break;
-	case SR_ERR_DEV_CLOSED:
+	case SR_ERR_DEVICE_CLOSED:
 		str = "device closed but should be open";
 		break;
 	case SR_ERR_CALL_STATUS:
@@ -147,8 +147,8 @@ SR_API const char *sr_error_name(int error_code)
 	case SR_ERR_NA:
 		str = "SR_ERR_NA";
 		break;
-	case SR_ERR_DEV_CLOSED:
-		str = "SR_ERR_DEV_CLOSED";
+	case SR_ERR_DEVICE_CLOSED:
+		str = "SR_ERR_DEVICE_CLOSED";
 		break;
 	case SR_ERR_CALL_STATUS:
 		str = "SR_ERR_CALL_STATUS";
diff --git a/libsigrok4DSL/hardware/DSL/dscope.c b/libsigrok4DSL/hardware/DSL/dscope.c
index d5cb2714..85720c4e 100644
--- a/libsigrok4DSL/hardware/DSL/dscope.c
+++ b/libsigrok4DSL/hardware/DSL/dscope.c
@@ -1975,8 +1975,10 @@ static int dev_acquisition_start(struct sr_dev_inst *sdi, void *cb_data)
     struct ctl_wr_cmd wr_cmd;
     GSList *l;
 
-    if (sdi->status != SR_ST_ACTIVE)
-        return SR_ERR_DEV_CLOSED;
+    if (sdi->status != SR_ST_ACTIVE){
+        ds_set_last_error(SR_ERR_DEVICE_CLOSED);
+        return SR_ERR_DEVICE_CLOSED;
+    }
 
     drvc = di->priv;
     devc = sdi->priv;
diff --git a/libsigrok4DSL/hardware/DSL/dsl.c b/libsigrok4DSL/hardware/DSL/dsl.c
index 9aa8fdfb..384f1c56 100644
--- a/libsigrok4DSL/hardware/DSL/dsl.c
+++ b/libsigrok4DSL/hardware/DSL/dsl.c
@@ -362,6 +362,7 @@ static int hw_dev_open(struct sr_dev_driver *di, struct sr_dev_inst *sdi)
         sr_err("Expected firmware version %d.%d, "
                 "got %d.%d.", DSL_REQUIRED_VERSION_MAJOR, DSL_REQUIRED_VERSION_MINOR,
                 vi.major, vi.minor);
+        ds_set_last_error(SR_ERR_DEVICE_FIRMWARE_VERSION_LOW);
         sdi->status = SR_ST_INCOMPATIBLE;
     }
     else {
@@ -1300,6 +1301,7 @@ SR_PRIV int dsl_fpga_config(struct libusb_device_handle *hdl, const char *filena
     if ((fw = fopen(filename, "rb")) == NULL) {
         sr_err("Unable to open FPGA bit file %s for reading: %s",
                filename, strerror(errno));
+        ds_set_last_error(SR_ERR_FIRMWARE_NOT_EXIST);
         return SR_ERR;
     }
 	
@@ -1866,6 +1868,7 @@ SR_PRIV int dsl_dev_open(struct sr_dev_driver *di, struct sr_dev_inst *sdi, gboo
 
         if (ret != LIBUSB_SUCCESS){
             dsl_dev_close(sdi);
+            ds_set_last_error(SR_ERR_DEVICE_IS_EXCLUSIVE);
             return SR_ERR;
         } 
     }
@@ -1914,6 +1917,7 @@ SR_PRIV int dsl_dev_open(struct sr_dev_driver *di, struct sr_dev_inst *sdi, gboo
             ret = dsl_hdl_version(sdi, &hw_info);
             if ((ret != SR_OK) || (hw_info != DSL_HDL_VERSION)) {
                sr_err("%s: HDL verison incompatible!", __func__);
+               ds_set_last_error(SR_ERR_DEVICE_FIRMWARE_VERSION_LOW);
                sdi->status = SR_ST_INCOMPATIBLE;
                return SR_ERR;
             }
diff --git a/libsigrok4DSL/hardware/DSL/dslogic.c b/libsigrok4DSL/hardware/DSL/dslogic.c
index bfb86915..dd61d08f 100644
--- a/libsigrok4DSL/hardware/DSL/dslogic.c
+++ b/libsigrok4DSL/hardware/DSL/dslogic.c
@@ -1415,8 +1415,10 @@ static int dev_acquisition_start(struct sr_dev_inst *sdi, void *cb_data)
     int ret;
     struct ctl_wr_cmd wr_cmd;
 
-    if (sdi->status != SR_ST_ACTIVE)
-        return SR_ERR_DEV_CLOSED;
+    if (sdi->status != SR_ST_ACTIVE){
+        ds_set_last_error(SR_ERR_DEVICE_CLOSED);
+        return SR_ERR_DEVICE_CLOSED;
+    }
 
     drvc = di->priv;
     devc = sdi->priv;
diff --git a/libsigrok4DSL/hardware/common/ezusb.c b/libsigrok4DSL/hardware/common/ezusb.c
index 60a0408b..16436a14 100644
--- a/libsigrok4DSL/hardware/common/ezusb.c
+++ b/libsigrok4DSL/hardware/common/ezusb.c
@@ -60,6 +60,7 @@ SR_PRIV int ezusb_install_firmware(libusb_device_handle *hdl,
     if ((fw = fopen(filename, "rb")) == NULL) {
         sr_err("Unable to open firmware file %s for reading: %s",
 		       filename, strerror(errno));
+		ds_set_last_error(SR_ERR_FIRMWARE_NOT_EXIST);
         return SR_ERR;
 	}
 
diff --git a/libsigrok4DSL/lib_main.c b/libsigrok4DSL/lib_main.c
index 28fb0cb7..e97cb3e4 100644
--- a/libsigrok4DSL/lib_main.c
+++ b/libsigrok4DSL/lib_main.c
@@ -69,6 +69,7 @@ struct sr_lib_context
 	int is_stop_by_detached;
 	int transaction_id;
 	int transaction_command;
+	int last_error;
 };
 
 static void hotplug_event_listen_callback(struct libusb_context *ctx, struct libusb_device *dev, int event);
@@ -104,6 +105,7 @@ static struct sr_lib_context lib_ctx = {
 	.is_stop_by_detached = 0,
 	.transaction_id = 0,
 	.transaction_command = DEV_TRANS_NONE,
+	.last_error = SR_OK,
 };
 
 /**
@@ -347,6 +349,8 @@ SR_API int ds_active_device(ds_device_handle handle)
 	int ret;
 	struct sr_dev_inst *old_dev;
 
+	lib_ctx.last_error = SR_OK;
+
 	if (handle == NULL_HANDLE)
 	{
 		return SR_ERR_ARG;
@@ -408,6 +412,7 @@ SR_API int ds_active_device(ds_device_handle handle)
 			}
 			else
 			{  
+				// Failed to switch new device.
 				if (old_dev != NULL && old_dev != dev){
 					sr_err("%s", "Open device error! the current device switch failed.");
 					lib_ctx.actived_device_instance = old_dev;
@@ -706,6 +711,8 @@ SR_API int ds_start_collect()
 	struct sr_dev_inst *di;
 	di = lib_ctx.actived_device_instance;
 
+	lib_ctx.last_error = SR_OK;
+
 	sr_info("%s", "Start collect.");
 
 	if (ds_is_collecting())
@@ -1650,3 +1657,13 @@ SR_PRIV int post_message_callback(int msg)
 }
 
 /**-------------------private function end---------------*/
+
+SR_PRIV void ds_set_last_error(int error)
+{
+	lib_ctx.last_error = error;
+}
+
+SR_API int ds_get_last_error()
+{
+	return lib_ctx.last_error;
+}
diff --git a/libsigrok4DSL/libsigrok-internal.h b/libsigrok4DSL/libsigrok-internal.h
index f735ed05..054e38da 100644
--- a/libsigrok4DSL/libsigrok-internal.h
+++ b/libsigrok4DSL/libsigrok-internal.h
@@ -407,6 +407,8 @@ SR_PRIV int sr_new_virtual_device(const char *filename, struct sr_dev_inst **out
  */
 SR_PRIV int sr_usb_device_is_exists(libusb_device *usb_dev);
 
+SR_PRIV void ds_set_last_error(int error);
+
 /**
  * Forward the data.
  */
diff --git a/libsigrok4DSL/libsigrok.h b/libsigrok4DSL/libsigrok.h
index 07857c35..e01e65da 100644
--- a/libsigrok4DSL/libsigrok.h
+++ b/libsigrok4DSL/libsigrok.h
@@ -74,9 +74,12 @@ enum {
 	SR_ERR_BUG        =  4, /**< Errors hinting at internal bugs. */
 	SR_ERR_SAMPLERATE =  5, /**< Incorrect samplerate. */
 	SR_ERR_NA         =  6, /**< Not applicable. */
-	SR_ERR_DEV_CLOSED =  7, /**< Device is closed, but needs to be open. */
-	SR_ERR_CALL_STATUS = 8, /**< Function call status error. */
-	SR_ERR_HAVE_DONE  = 9, /**< The Function have called.*/
+	SR_ERR_DEVICE_CLOSED =  7, /**< Device is closed, but needs to be open. */
+	SR_ERR_CALL_STATUS 	 =  8, /**< Function call status error. */
+	SR_ERR_HAVE_DONE  	 =  9, /**< The Function have called.*/
+	SR_ERR_FIRMWARE_NOT_EXIST 	= 10, /**< The firmware file is not exist.*/
+	SR_ERR_DEVICE_IS_EXCLUSIVE 	= 11, /**< The device is exclusive by other process.*/
+	SR_ERR_DEVICE_FIRMWARE_VERSION_LOW = 12, /**< The firmware version is too low.*/
 
 	/*
 	 * Note: When adding entries here, don't forget to also update the
@@ -1470,6 +1473,8 @@ SR_API int ds_is_collecting();
  */
 SR_API int ds_release_actived_device();
 
+SR_API int ds_get_last_error();
+
 /*---config -----------------------------------------------*/
 SR_API int ds_get_actived_device_config(const struct sr_channel *ch,
                          const struct sr_channel_group *cg,