diff --git a/examples/device_exam.cpp b/examples/device_exam.cpp
index 5e46edd..73ff9fb 100644
--- a/examples/device_exam.cpp
+++ b/examples/device_exam.cpp
@@ -20,6 +20,8 @@ int main()
         },
         std::tuple<double, long>{});
 
+    dev.addAttr("2", [&d]() -> adc_result_t<double> { return d; }, nullptr);
+
     adc_result_t<int> ri = dev["1"];
     if (ri) {
         std::println("dev[1] = {}", ri.value());
@@ -39,5 +41,17 @@ int main()
         std::println("cannot get dev[1] as double: {}", rd.error().message());
     }
 
+    ri = dev["1"];
+    if (ri) {
+        std::println("dev[1] = {}", ri.value());
+    } else {
+        std::println("cannot get dev[1] as int: {}", ri.error().message());
+    }
+
+    err = dev["2"] = 0.29817;
+    if (err) {
+        std::println("cannot set dev[2] as double: {}", err.message());
+    }
+
     return 0;
 }
\ No newline at end of file
diff --git a/include/adclib/adclib_device.h b/include/adclib/adclib_device.h
index e07f45e..1b1dda8 100644
--- a/include/adclib/adclib_device.h
+++ b/include/adclib/adclib_device.h
@@ -13,7 +13,7 @@
 #include <utility>
 
 
-// #include <snipplib/concepts/snplib_concepts.h>
+#include <snipplib/concepts/snplib_traits.h>
 #include <snipplib/containers/snplib_hmap.h>
 #include <snipplib/serialization/snplib_serialization.h>
 
@@ -102,6 +102,29 @@ inline std::error_code make_error_code(AdcDeviceErrorCode ec)
 }
 
 
+namespace details
+{
+
+template <typename T>
+concept snplib_getter_c = std::same_as<T, std::nullptr_t> || requires(T t) {
+    { t() } -> adc_result_c;
+};
+
+template <typename T>
+concept snplib_setter_c =
+    std::same_as<T, std::nullptr_t> || (snplib::snplib_callable_c<T> && (snplib::snplib_func_traits_t<T>::arity >= 1) &&
+                                        std::same_as<adc_error_t, typename snplib::snplib_func_traits_t<T>::ret_t>);
+
+
+// deduce value type from getter and setter
+template <snplib_getter_c GT, snplib_setter_c ST>
+using snplib_attr_value_deduced_t =
+    std::conditional_t<std::is_null_pointer_v<GT>,
+                       std::conditional_t<std::is_null_pointer_v<ST>, void, snplib::snplib_func_arg1_t<ST>>,
+                       typename std::invoke_result_t<GT>::value_type>;
+
+}  // namespace details
+
 template <std::formattable<char> ATTR_ID_T = std::string_view, std::formattable<char> CMD_ID_T = std::string_view>
 class AdcGenericDevice
 {
@@ -159,7 +182,11 @@ protected:
         {
             auto const& attr = _dev._attrs.template get<attr_t<VT>>(_id);
             if (attr) {
-                return attr.value().getter();
+                if (attr.value().getter) {
+                    return attr.value().getter();
+                }
+
+                return std::unexpected(AdcDeviceErrorCode::ERROR_WO_ATTR);
             }
 
             // error
@@ -175,7 +202,11 @@ protected:
         {
             auto const& attr = _dev._attrs.template get<attr_t<VT>>(_id);
             if (attr) {
-                return attr.value().setter(std::forward<VT>(val));
+                if (attr.value().setter) {
+                    return attr.value().setter(std::forward<VT>(val));
+                }
+
+                return AdcDeviceErrorCode::ERROR_RO_ATTR;
             }
 
             if (attr.error() == snplib::HeterogenMap<ATTR_ID_T>::ERROR_NO_ELEM) {
@@ -197,6 +228,8 @@ public:
     typedef ATTR_ID_T attr_id_t;
     typedef CMD_ID_T cmd_id_t;
 
+    enum AttrAccessType { ATTR_ACCESS_RW, ATTR_ACCESS_RO, ATTR_ACCESS_WO };
+
     AdcGenericDevice() {}
 
     template <snplib::snplib_callable_c ET>
@@ -205,18 +238,30 @@ public:
         _commands.emplace(std::move(id), std::forward<ET>(exec_func));
     }
 
-    template <typename GT, typename ST, typename... VTs>
+    // template <typename GT, typename ST, typename... VTs>
+    template <details::snplib_getter_c GT, details::snplib_setter_c ST, typename... VTs>
     void addAttr(ATTR_ID_T id, GT&& getter, ST&& setter, std::tuple<VTs...> = std::tuple())
     {
-        // deduce attribute value type
-        using ret_t = std::invoke_result_t<GT>;
-        using v_t = typename ret_t::value_type;
+        // static_assert(!(std::is_null_pointer_v<GT> && std::is_null_pointer_v<ST>),
+        //               "Getter and setter cannot be nullptr_t at the same time!");
 
-        static_assert(adc_result_c<ret_t>, "Invalid return type of the getter!");
+        // // deduce attribute value type
+        // using ret_t = std::invoke_result_t<GT>;
 
-        static_assert(std::invocable<ST, v_t const&>, "Invalid setter type!");
-        static_assert(std::convertible_to<std::invoke_result_t<ST, v_t const&>, adc_error_t>,
-                      "Invalid return type of the setter!");
+        // static_assert(adc_result_c<ret_t>, "Invalid return type of the getter!");
+
+        // using v_t = typename ret_t::value_type;
+
+        // static_assert(std::invocable<ST, v_t const&>, "Invalid setter type!");
+        // static_assert(std::convertible_to<std::invoke_result_t<ST, v_t const&>, adc_error_t>,
+        //               "Invalid return type of the setter!");
+
+        using v_t = details::snplib_attr_value_deduced_t<GT, ST>;
+        static_assert(!std::is_void_v<v_t>, "Getter and setter cannot be nullptr_t at the same time!");
+
+        if constexpr (!std::is_null_pointer_v<GT> && !std::is_null_pointer_v<ST>) {
+            static_assert(std::invocable<ST, v_t const&>, "Invalid setter argument type!");
+        }
 
         _attrs.push(std::move(id), attr_t<v_t>{.getter = std::forward<GT>(getter), .setter = std::forward<ST>(setter)});
 
@@ -229,7 +274,22 @@ public:
         //                       }) {
         //             static_assert(false, "Invalid user type!");
         //         }
-        //         _attrs.push(std::move(id), attr_t<u_t>{.getter = []() {}, .setter = []() {}});
+
+        //         if constexpr (!std::same_as<u_t, v_t>) {
+        //             _attrs.push(std::move(id), attr_t<u_t>{.getter = [id, this]() -> adc_result_t<u_t> {
+        //                                                        auto const& attr = _attrs.template
+        //                                                        get<attr_t<v_t>>(id); if (attr) {
+        //                                                            adc_result_t v = attr.getter();
+        //                                                            if (v) {
+        //                                                                return
+        //                                                                adc_result_t(static_cast<u_t>(v.value()));
+        //                                                            }
+        //                                                        }
+
+        //                                                        return AdcDeviceErrorCode::ERROR_UNKNOWN;
+        //                                                    },
+        //                                                    .setter = []() {}});
+        //         }
         //     };
         // }
     }
@@ -243,20 +303,22 @@ public:
         return AdcDeviceErrorCode::ERROR_NO_CMD_ID;
     }
 
+    auto operator[](ATTR_ID_T id)
+    {
+        return attr_proxy_t{*this, std::move(id)};
+    }
+
 
     template <typename VT>
     adc_result_t<VT> attr(ATTR_ID_T id)
     {
+        return attr_proxy_t{*this, std::move(id)};
     }
 
     template <typename VT>
     adc_error_t attr(ATTR_ID_T id, VT const& v)
     {
-    }
-
-    auto operator[](ATTR_ID_T id)
-    {
-        return attr_proxy_t{*this, std::move(id)};
+        return attr_proxy_t{*this, std::move(id)} = v;
     }
 };