diff --git a/components/script/CMakeLists.txt b/components/script/CMakeLists.txt
index 79eb010..238b8bb 100644
--- a/components/script/CMakeLists.txt
+++ b/components/script/CMakeLists.txt
@@ -41,7 +41,6 @@ set(srcs
     "src/l_aux_lib.c"
     "src/l_board_config_lib.c"
     "src/l_serial_lib.c"
-    "src/l_modbus_lib.c"
     )
 
 idf_component_register(SRC_DIRS "src" "lib/lua" "lib/yaml/src"
diff --git a/components/script/src/l_component.c b/components/script/src/l_component.c
index 479b808..1b71697 100644
--- a/components/script/src/l_component.c
+++ b/components/script/src/l_component.c
@@ -115,47 +115,44 @@ static void l_process_params(lua_State* L, component_param_list_t* param_list)
     lua_remove(L, -2);
 }
 
-static void component_process_params(lua_State* L, component_entry_t* component_entry)
+static void component_process_params(lua_State* L, component_entry_t* component)
 {
-    luaL_unref(L, LUA_REGISTRYINDEX, component_entry->params_ref);
+    luaL_unref(L, LUA_REGISTRYINDEX, component->params_ref);
 
-    component_param_list_t* param_list = component_params_read(component_entry->id);
+    component_param_list_t* param_list = component_params_read(component->id);
 
-    lua_rawgeti(L, LUA_REGISTRYINDEX, component_entry->params_def_ref);
+    lua_rawgeti(L, LUA_REGISTRYINDEX, component->params_def_ref);
 
     l_process_params(L, param_list);
-    component_entry->params_ref = luaL_ref(L, LUA_REGISTRYINDEX);
+    component->params_ref = luaL_ref(L, LUA_REGISTRYINDEX);
 
     if (param_list) component_params_free(param_list);
 }
 
-static void component_restart_coroutine(lua_State* L, component_entry_t* component_entry)
+static void component_restart_coroutine(lua_State* L, component_entry_t* component)
 {
     // end previous coroutine
-    lua_rawgeti(L, LUA_REGISTRYINDEX, component_entry->coroutine_ref);
+    lua_rawgeti(L, LUA_REGISTRYINDEX, component->coroutine_ref);
     if (lua_isthread(L, -1)) {
         lua_State* co = lua_tothread(L, -1);
         if (lua_status(co) == LUA_YIELD) {
-            int nresults = 0;
-            lua_pushboolean(co, false);
-            int status = lua_resume(co, L, 1, &nresults);
-            lua_pop(co, nresults);
-
-            if (status == LUA_YIELD) {
-                ESP_LOGI(TAG, "Coroutine not stop itself");
-                lua_closethread(L, co);
-            }
+            lua_closethread(L, co);
+        } else {
+            lua_pop(L, 1);
         }
+    } else {
+        lua_pop(L, 1);
     }
-    lua_pop(L, 1);
 
-    luaL_unref(L, LUA_REGISTRYINDEX, component_entry->coroutine_ref);
-    component_entry->coroutine_ref = LUA_NOREF;
-    component_entry->resume_after = 0;
+    luaL_unref(L, LUA_REGISTRYINDEX, component->coroutine_ref);
+    component->coroutine_ref = LUA_NOREF;
+    component->resume_after = 0;
+
+    lua_gc(L, LUA_GCCOLLECT, 0);
 
     // start new coroutine
-    lua_rawgeti(L, LUA_REGISTRYINDEX, component_entry->start_ref);
-    lua_rawgeti(L, LUA_REGISTRYINDEX, component_entry->params_ref);
+    lua_rawgeti(L, LUA_REGISTRYINDEX, component->start_ref);
+    lua_rawgeti(L, LUA_REGISTRYINDEX, component->params_ref);
     if (lua_pcall(L, 1, 1, 0) != LUA_OK) {
         const char* err = lua_tostring(L, -1);
         lua_writestring(err, strlen(err));
@@ -163,7 +160,7 @@ static void component_restart_coroutine(lua_State* L, component_entry_t* compone
         lua_pop(L, 1);
     } else {
         if (lua_isthread(L, -1)) {
-            component_entry->coroutine_ref = luaL_ref(L, LUA_REGISTRYINDEX);
+            component->coroutine_ref = luaL_ref(L, LUA_REGISTRYINDEX);
         } else {
             lua_pop(L, 1);
         }
@@ -202,28 +199,28 @@ static int l_add_component(lua_State* L)
     lua_pop(L, 1);
 
     component_list_t* component_list = get_component_list(L);
-    component_entry_t* component_entry;
-    SLIST_FOREACH (component_entry, component_list, entries) {
-        if (strcmp(id, component_entry->id) == 0) {
+    component_entry_t* component;
+    SLIST_FOREACH (component, component_list, entries) {
+        if (strcmp(id, component->id) == 0) {
             luaL_argerror(L, 1, "component with duplicate id");
         }
     }
 
-    component_entry = (component_entry_t*)malloc(sizeof(component_entry_t));
-    component_entry->id = strdup(id);
-    component_entry->name = strdup(name);
-    component_entry->description = description ? strdup(description) : NULL;
+    component = (component_entry_t*)malloc(sizeof(component_entry_t));
+    component->id = strdup(id);
+    component->name = strdup(name);
+    component->description = description ? strdup(description) : NULL;
     lua_getfield(L, 1, "params");
-    component_entry->params_def_ref = luaL_ref(L, LUA_REGISTRYINDEX);
+    component->params_def_ref = luaL_ref(L, LUA_REGISTRYINDEX);
     lua_getfield(L, 1, "start");
-    component_entry->start_ref = luaL_ref(L, LUA_REGISTRYINDEX);
-    component_entry->params_ref = LUA_NOREF;
-    component_entry->coroutine_ref = LUA_NOREF;
+    component->start_ref = luaL_ref(L, LUA_REGISTRYINDEX);
+    component->params_ref = LUA_NOREF;
+    component->coroutine_ref = LUA_NOREF;
 
-    component_process_params(L, component_entry);
-    component_restart_coroutine(L, component_entry);
+    component_process_params(L, component);
+    component_restart_coroutine(L, component);
 
-    SLIST_INSERT_HEAD(component_list, component_entry, entries);
+    SLIST_INSERT_HEAD(component_list, component, entries);
 
     return 0;
 }
@@ -262,20 +259,19 @@ void l_component_register(lua_State* L)
     components_ref = luaL_ref(L, LUA_REGISTRYINDEX);
 }
 
-void l_component_resume(lua_State* L, bool finalize)
+void l_component_resume(lua_State* L)
 {
     component_list_t* component_list = get_component_list(L);
     component_entry_t* component;
     SLIST_FOREACH (component, component_list, entries) {
-        if (finalize || component->resume_after == 0 || component->resume_after < xTaskGetTickCount()) {
+        if (component->resume_after == 0 || component->resume_after < xTaskGetTickCount()) {
             lua_rawgeti(L, LUA_REGISTRYINDEX, component->coroutine_ref);
             if (lua_isthread(L, -1)) {
                 lua_State* co = lua_tothread(L, -1);
                 int status = lua_status(co);
                 if (status == LUA_YIELD || status == LUA_OK) {
                     int nresults = 0;
-                    lua_pushboolean(co, !finalize);
-                    status = lua_resume(co, L, 1, &nresults);
+                    status = lua_resume(co, L, 0, &nresults);
                     if (status == LUA_YIELD || status == LUA_OK) {
                         if (nresults > 0 && lua_isinteger(co, -nresults)) {
                             component->resume_after = xTaskGetTickCount() + pdMS_TO_TICKS(lua_tointeger(co, -nresults));
diff --git a/components/script/src/l_component.h b/components/script/src/l_component.h
index 2a23ba1..66adc7d 100644
--- a/components/script/src/l_component.h
+++ b/components/script/src/l_component.h
@@ -8,7 +8,7 @@
 
 void l_component_register(lua_State* L);
 
-void l_component_resume(lua_State* L, bool finalize);
+void l_component_resume(lua_State* L);
 
 script_component_list_t* l_component_get_components(lua_State* L);
 
diff --git a/components/script/src/l_modbus_lib.c b/components/script/src/l_modbus_lib.c
deleted file mode 100644
index b94f997..0000000
--- a/components/script/src/l_modbus_lib.c
+++ /dev/null
@@ -1,42 +0,0 @@
-#include "l_modbus_lib.h"
-
-#include <esp_log.h>
-
-#include "lauxlib.h"
-#include "lua.h"
-
-#define BUF_SIZE 256
-
-// @todo
-
-// static const char* TAG = "l_modbus";
-
-// static int l_get_available(lua_State* L)
-// {
-
-//     return 0;
-// }
-
-// static int l_read(lua_State* L)
-// {
-
-//     return 0;
-// }
-
-// static int l_write(lua_State* L)
-// {
-
-//     return 0;
-// }
-
-static const luaL_Reg lib[] = {
-    // { "getavailable", l_get_available },
-    { NULL, NULL },
-};
-
-int luaopen_modbus(lua_State* L)
-{
-    luaL_newlib(L, lib);
-
-    return 1;
-}
diff --git a/components/script/src/l_modbus_lib.h b/components/script/src/l_modbus_lib.h
deleted file mode 100644
index dcaac4a..0000000
--- a/components/script/src/l_modbus_lib.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef L_MODBUS_LIB_H_
-#define L_MODBUS_LIB_H_
-
-#include "lua.h"
-
-int luaopen_modbus(lua_State* L);
-
-#endif /* L_MODBUS_LIB_H_ */
diff --git a/components/script/src/l_serial_lib.c b/components/script/src/l_serial_lib.c
index 67c0617..451b071 100644
--- a/components/script/src/l_serial_lib.c
+++ b/components/script/src/l_serial_lib.c
@@ -8,24 +8,33 @@
 
 #define BUF_SIZE 256
 
-// static const char* TAG = "l_serial";
+static const char* TAG = "l_serial";
 
-static int l_get_available(lua_State* L)
+static bool is_opened;
+
+static int l_open(lua_State* L)
 {
-    lua_pushboolean(L, serial_script_is_available());
+    ESP_LOGW(TAG, "l_open");
+
+    if (!serial_script_is_available() || is_opened) {
+        lua_pushnil(L);
+    } else {
+        is_opened = true;
+        lua_newtable(L);
+        luaL_setmetatable(L, "serial.port");
+    }
+
     return 1;
 }
 
-static int l_read(lua_State* L)
+static int l_port_read(lua_State* L)
 {
+    ESP_LOGW(TAG, "l_port_read");
+
     char buf[BUF_SIZE];
     size_t len = BUF_SIZE;
-    uint32_t timeout = 0;
-    if (!lua_isnoneornil(L, 1)) {
-        timeout = luaL_checkinteger(L, 1);
-    }
 
-    if (serial_script_read(buf, &len, timeout) != ESP_OK) {
+    if (serial_script_read(buf, &len) != ESP_OK) {
         luaL_error(L, "serial error");
     }
 
@@ -38,38 +47,82 @@ static int l_read(lua_State* L)
     return 1;
 }
 
-static int l_write(lua_State* L)
+static int l_port_write(lua_State* L)
 {
+    ESP_LOGW(TAG, "l_port_write");
+
     size_t len;
     const char* buf;
     char buf_num;
 
-    if (lua_isnumber(L, 1)) {
-        buf_num = lua_tonumber(L, 1);
+    if (lua_isnumber(L, 2)) {
+        buf_num = lua_tonumber(L, 2);
         len = 1;
         buf = &buf_num;
-    } else if (lua_isstring(L, 1)) {
-        buf = lua_tolstring(L, 1, &len);
+    } else if (lua_isstring(L, 2)) {
+        buf = lua_tolstring(L, 2, &len);
     } else {
-        luaL_error(L, "argument must be number or string");
+        luaL_argerror(L, 2, "argument must be number or string");
         return 0;
     }
 
-    serial_script_write(buf, len);
+    if (serial_script_write(buf, len) != ESP_OK) {
+        luaL_error(L, "serial error");
+    }
+
+    return 0;
+}
+
+static int l_port_flush(lua_State* L)
+{
+    ESP_LOGW(TAG, "l_port_flush");
+
+    if (serial_script_flush() != ESP_OK) {
+        luaL_error(L, "serial error");
+    }
+
+    return 0;
+}
+
+static int l_port_gc(lua_State* L)
+{
+    ESP_LOGW(TAG, "l_port_gc");
+
+    is_opened = false;
 
     return 0;
 }
 
 static const luaL_Reg lib[] = {
-    { "getavailable", l_get_available },
-    { "read", l_read },
-    { "write", l_write },
+    { "open", l_open },
+    { NULL, NULL },
+};
+
+static const luaL_Reg port_fields[] = {
+    { "write", l_port_write },
+    { "read", l_port_read },
+    { "flush", l_port_flush },
+    { NULL, NULL },
+};
+
+static const luaL_Reg port_metadata[] = {
+    { "__index", NULL },
+    { "__gc", l_port_gc },
     { NULL, NULL },
 };
 
 int luaopen_serial(lua_State* L)
 {
+    is_opened = false;
+
     luaL_newlib(L, lib);
 
+    luaL_newmetatable(L, "serial.port");
+    luaL_setfuncs(L, port_metadata, 0);
+    luaL_newlibtable(L, port_fields);
+    luaL_setfuncs(L, port_fields, 0);
+    lua_setfield(L, -2, "__index");
+    lua_pop(L, 1);
+
     return 1;
 }
diff --git a/components/script/src/script.c b/components/script/src/script.c
index 4d52ea8..9ede294 100644
--- a/components/script/src/script.c
+++ b/components/script/src/script.c
@@ -14,7 +14,6 @@
 #include "l_component.h"
 #include "l_evse_lib.h"
 #include "l_json_lib.h"
-#include "l_modbus_lib.h"
 #include "l_mqtt_lib.h"
 #include "l_serial_lib.h"
 #include "lauxlib.h"
@@ -25,9 +24,7 @@
 #include "script_utils.h"
 #include "script_watchdog.h"
 
-#define START_TIMEOUT       10000
 #define SHUTDOWN_TIMEOUT    1000
-#define HEARTBEAT_THRESHOLD 5
 #define OUTPUT_BUFFER_SIZE  4096
 
 #define NVS_NAMESPACE   "script"
@@ -83,9 +80,6 @@ static void script_task_func(void* param)
     luaL_requiref(L, "serial", luaopen_serial, 0);
     lua_pop(L, 1);
 
-    luaL_requiref(L, "modbus", luaopen_modbus, 0);
-    lua_pop(L, 1);
-
     lua_gc(L, LUA_GCSETPAUSE, 110);
     lua_gc(L, LUA_GCSETSTEPMUL, 200);
 
@@ -108,7 +102,7 @@ static void script_task_func(void* param)
         }
         xSemaphoreTake(script_mutex, portMAX_DELAY);
         script_watchdog_reset();
-        l_component_resume(L, false);
+        l_component_resume(L);
         xSemaphoreGive(script_mutex);
 
         int top = lua_gettop(L);
@@ -119,8 +113,6 @@ static void script_task_func(void* param)
         vTaskDelay(pdMS_TO_TICKS(50));
     }
 
-    l_component_resume(L, true);
-
     lua_close(L);
     L = NULL;
 
diff --git a/components/serial/include/serial_script.h b/components/serial/include/serial_script.h
index 3c76c17..37dcd2e 100644
--- a/components/serial/include/serial_script.h
+++ b/components/serial/include/serial_script.h
@@ -25,6 +25,8 @@ bool serial_script_is_available(void);
 
 esp_err_t serial_script_write(const char *buf, size_t len);
 
-esp_err_t serial_script_read(char *buf, size_t *len, uint32_t timeout);
+esp_err_t serial_script_read(char *buf, size_t *len);
+
+esp_err_t serial_script_flush(void);
 
 #endif /* SERIAL_SCRIPT_H_ */
diff --git a/components/serial/src/serial_script.c b/components/serial/src/serial_script.c
index 2996eee..efc3b06 100644
--- a/components/serial/src/serial_script.c
+++ b/components/serial/src/serial_script.c
@@ -1,10 +1,10 @@
 #include "serial_script.h"
 
-#include <driver/uart_vfs.h>
 #include <esp_log.h>
 
 #define BUF_SIZE         256
 #define EVENT_QUEUE_SIZE 20
+#define VFS_PATH         "/dev/serial"
 
 static const char* TAG = "serial_script";
 
@@ -35,7 +35,7 @@ void serial_script_start(uart_port_t uart_num, uint32_t baud_rate, uart_word_len
         ESP_LOGE(TAG, "uart_driver_install() returned 0x%x", err);
         return;
     }
-    uart_vfs_dev_use_driver(uart_num);
+
     port = uart_num;
 
     if (rs485) {
@@ -81,14 +81,26 @@ esp_err_t serial_script_write(const char* buf, size_t len)
     return ESP_OK;
 }
 
-esp_err_t serial_script_read(char* buf, size_t* len, uint32_t timeout)
+esp_err_t serial_script_flush(void)
+{
+    if (port == -1) {
+        ESP_LOGW(TAG, "No script serial available");
+        return ESP_ERR_NOT_FOUND;
+    }
+
+    uart_flush(port);
+
+    return ESP_OK;
+}
+
+esp_err_t serial_script_read(char* buf, size_t* len)
 {
     if (port == -1) {
         ESP_LOGW(TAG, "No script serial available");
         return ESP_ERR_NOT_FOUND;
     }
 
-    *len = uart_read_bytes(port, buf, *len, pdMS_TO_TICKS(timeout));
+    *len = uart_read_bytes(port, buf, *len, 0);
 
     return ESP_OK;
 }
\ No newline at end of file
diff --git a/test_app/main/component1.lua b/test_app/main/component1.lua
index 944a7c5..90145c0 100644
--- a/test_app/main/component1.lua
+++ b/test_app/main/component1.lua
@@ -23,13 +23,12 @@ addcomponent({
         paramnumber1 = tostring(params.number1)
         paramboolean1 = tostring(params.boolean1)
         return coroutine.create(function()
-            stage = "begin"
             local counter = 1
-            while coroutine.yield(1000) do
+            while true do
                 stage = "loop" .. counter
                 counter = counter + 1
+                coroutine.yield(1000)
             end
-            stage = "end"
         end)
     end
 })
diff --git a/test_app/main/main.c b/test_app/main/main.c
index c9f3e22..6bcb169 100644
--- a/test_app/main/main.c
+++ b/test_app/main/main.c
@@ -15,7 +15,7 @@
 
 static void run_all_tests(void)
 {
-    // RUN_TEST_GROUP(evse);
+    RUN_TEST_GROUP(evse);
     RUN_TEST_GROUP(script);
 }
 
diff --git a/test_app/main/test_script.c b/test_app/main/test_script.c
index 8024861..b4c575d 100644
--- a/test_app/main/test_script.c
+++ b/test_app/main/test_script.c
@@ -265,29 +265,29 @@ TEST(script, component)
     script_component_params_free(component_params);
 
     // test yield/resume
-    l_component_resume(L, false);
-    TEST_ASSERT_EQUAL_STRING("begin", get_global_var("stage"));
+    l_component_resume(L);
+    TEST_ASSERT_EQUAL_STRING("loop1", get_global_var("stage"));
 
-    vTaskStepTick(pdMS_TO_TICKS(1100));
-    l_component_resume(L, false);
+    l_component_resume(L);
     TEST_ASSERT_EQUAL_STRING("loop1", get_global_var("stage"));
 
     vTaskStepTick(pdMS_TO_TICKS(1100));
-    l_component_resume(L, false);
+    l_component_resume(L);
     TEST_ASSERT_EQUAL_STRING("loop2", get_global_var("stage"));
 
+    vTaskStepTick(pdMS_TO_TICKS(1100));
+    l_component_resume(L);
+    TEST_ASSERT_EQUAL_STRING("loop3", get_global_var("stage"));
+
     l_component_restart(L, "component1");
     TEST_ASSERT_EQUAL_STRING("start", get_global_var("stage"));
 
-    l_component_resume(L, false);
-    TEST_ASSERT_EQUAL_STRING("begin", get_global_var("stage"));
-
-    vTaskStepTick(pdMS_TO_TICKS(1100));
-    l_component_resume(L, false);
+    l_component_resume(L);
     TEST_ASSERT_EQUAL_STRING("loop1", get_global_var("stage"));
 
-    l_component_resume(L, true);
-    TEST_ASSERT_EQUAL_STRING("end", get_global_var("stage"));
+    vTaskStepTick(pdMS_TO_TICKS(1100));
+    l_component_resume(L);
+    TEST_ASSERT_EQUAL_STRING("loop2", get_global_var("stage"));
 
     TEST_ASSERT_EQUAL(0, lua_gettop(L));  // after all Lua stack should be empty
 }
@@ -452,10 +452,10 @@ TEST(script, json)
 
 TEST_GROUP_RUNNER(script)
 {
-    // RUN_TEST_CASE(script, watchdog);
+    RUN_TEST_CASE(script, watchdog);
     RUN_TEST_CASE(script, component);
-    // RUN_TEST_CASE(script, component_params);
-    // RUN_TEST_CASE(script, evse);
-    // RUN_TEST_CASE(script, board_config)
-    // RUN_TEST_CASE(script, json);
+    RUN_TEST_CASE(script, component_params);
+    RUN_TEST_CASE(script, evse);
+    RUN_TEST_CASE(script, board_config)
+    RUN_TEST_CASE(script, json);
 }
\ No newline at end of file