diff --git a/hardware/hardware.cpp b/hardware/hardware.cpp
index 6c5c87e..6cdf077 100644
--- a/hardware/hardware.cpp
+++ b/hardware/hardware.cpp
@@ -198,8 +198,8 @@ char* scanner_hw::get_value(const char* name, void* value, size_t* size, int* er
 
     if(strcmp(name, SANE_FULL_NAME(PAPER_ON)) == 0)
     {
-        ret = (char*)malloc(4);
-        memset(ret, 0, 4);
+        ret = (char*)malloc(sizeof(int));
+        *(int*)ret = 0;
         *(bool*)ret = paper_on_;
         if(size)
             *size = sizeof(bool);
diff --git a/sdk/sane_opt_json/base_opt.cpp b/sdk/sane_opt_json/base_opt.cpp
index 70ae256..63069d2 100644
--- a/sdk/sane_opt_json/base_opt.cpp
+++ b/sdk/sane_opt_json/base_opt.cpp
@@ -2,6 +2,8 @@
 
 #include <json/gb_json.h>
 #include <huagao/hgscanner_error.h>
+#include <sane/sane_ex.h>
+#include <string.h>
 
 
 sane_opt_provider::sane_opt_provider()
@@ -16,6 +18,20 @@ sane_opt_provider::~sane_opt_provider()
 	following_.clear();
 }
 
+std::string sane_opt_provider::sane_value_2_text(const char* type, void* value)
+{
+	if(strcmp(type, JSON_SANE_TYPE_BOOL) == 0)
+		return *(bool*)value ? "true" : "false";
+	else if(strcmp(type, JSON_SANE_TYPE_INT) == 0)
+		return std::to_string(*(int*)value);
+	else if(strcmp(type, JSON_SANE_TYPE_FIXED) == 0)
+		return std::to_string(*(double*)value);
+	else if(strcmp(type, JSON_SANE_TYPE_STRING) == 0)
+		return (char*)value;
+	else
+		return "";
+}
+
 bool sane_opt_provider::set_opt_json_text(char* txt)
 {
 	gb_json* jsn = new gb_json();
diff --git a/sdk/sane_opt_json/base_opt.h b/sdk/sane_opt_json/base_opt.h
index 6f163cd..cb87518 100644
--- a/sdk/sane_opt_json/base_opt.h
+++ b/sdk/sane_opt_json/base_opt.h
@@ -22,6 +22,8 @@ protected:
 public:
 	sane_opt_provider();
 
+	static std::string sane_value_2_text(const char* type, void* value);	// convert to readable text. e.g. bool to "true" or "false", ...
+
 protected:
 	virtual ~sane_opt_provider();
 
diff --git a/sdk/sane_opt_json/device_opt.cpp b/sdk/sane_opt_json/device_opt.cpp
index 59aa556..b5c3942 100644
--- a/sdk/sane_opt_json/device_opt.cpp
+++ b/sdk/sane_opt_json/device_opt.cpp
@@ -1716,8 +1716,9 @@ bool device_option::refine_data(const char* name, void* value)
 	now_->get_value(name, child);
 	if (child)
 	{
-		std::string type("");
+		std::string type(""), org(""), result("");
 		child->get_value("type", type);
+		org = sane_opt_provider::sane_value_2_text(type.c_str(), value);
 		if (type == JSON_SANE_TYPE_BOOL)
 		{
 			refined = refine_data_to_range<bool>(child, value);
@@ -1734,6 +1735,11 @@ bool device_option::refine_data(const char* name, void* value)
 		{
 			refined = refine_string_data(child, value);
 		}
+		if(refined)
+		{
+			result = sane_opt_provider::sane_value_2_text(type.c_str(), value);
+			utils::to_log(LOG_LEVEL_DEBUG, "Refine value of '%s' from '%s' to '%s'.\n", name, org.c_str(), result.c_str());
+		}
 
 		child->release();
 	}
@@ -1788,11 +1794,13 @@ int device_option::update_data(const char* name, void* value, bool reorder_if_ne
 					}
 				}
 
+				child->get_value("type", type);
+				utils::to_log(LOG_LEVEL_DEBUG, "set option '%s' value to '%s' = %d.\n", name, sane_opt_provider::sane_value_2_text(type.c_str(), value).c_str(), err);
+
 				if (err == SCANNER_ERR_OK || err == SCANNER_ERR_NOT_EXACT
 					|| err == SCANNER_ERR_RELOAD_IMAGE_PARAM || err == SCANNER_ERR_RELOAD_OPT_PARAM
 					|| err == SCANNER_ERR_CONFIGURATION_CHANGED)
 				{
-					child->get_value("type", type);
 					if (type == JSON_SANE_TYPE_BOOL)
 					{
 						child->set_value("cur", *(bool*)value);