diff --git a/CMakeLists.txt b/CMakeLists.txt
index a33ac7e..dd6d722 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -43,10 +43,10 @@ set(srcs
     "common/esp_modbus_master_serial.c"
     "common/esp_modbus_slave_serial.c")
 
-set(include_dirs common/include)
+set(include_dirs port common/include modbus/include)
 
-set(priv_include_dirs common port modbus modbus/ascii modbus/functions
-                      modbus/rtu modbus/tcp modbus/include)
+set(priv_include_dirs port common modbus modbus/ascii modbus/functions
+                      modbus/rtu modbus/tcp)
 
 list(APPEND priv_include_dirs serial_slave/port serial_slave/modbus_controller
      serial_master/port serial_master/modbus_controller
diff --git a/freemodbus/common/include/esp_modbus_common.h b/freemodbus/common/include/esp_modbus_common.h
index f443286..6f2c290 100644
--- a/freemodbus/common/include/esp_modbus_common.h
+++ b/freemodbus/common/include/esp_modbus_common.h
@@ -9,14 +9,17 @@
 
 #include "driver/uart.h"                    // for UART types
 
+#include "port.h"
+#include "mbproto.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #if __has_include("esp_check.h")
+
 #include "esp_check.h"
 #include "esp_log.h"
-
 #define MB_RETURN_ON_FALSE(a, err_code, tag, format, ...) ESP_RETURN_ON_FALSE(a, err_code, tag, format __VA_OPT__(,) __VA_ARGS__)
 
 #else
diff --git a/freemodbus/common/include/esp_modbus_master.h b/freemodbus/common/include/esp_modbus_master.h
index d11ade7..0b6b5e3 100644
--- a/freemodbus/common/include/esp_modbus_master.h
+++ b/freemodbus/common/include/esp_modbus_master.h
@@ -94,12 +94,14 @@ typedef struct {
     mb_param_perms_t    access;             /*!< Access permissions based on mode */
 } mb_parameter_descriptor_t;
 
-/**
+typedef enum eMbCommands_t mb_function_codes_t;
+
+/**<
  * @brief Modbus register request type structure
  */
 typedef struct {
     uint8_t slave_addr;             /*!< Modbus slave address */
-    uint8_t command;                /*!< Modbus command to send */
+    mb_function_codes_t command;    /*!< Modbus command to send */
     uint16_t reg_start;             /*!< Modbus start register */
     uint16_t reg_size;              /*!< Modbus number of registers */
 } mb_param_request_t;
diff --git a/freemodbus/modbus/include/mbproto.h b/freemodbus/modbus/include/mbproto.h
index da303a6..cff6960 100644
--- a/freemodbus/modbus/include/mbproto.h
+++ b/freemodbus/modbus/include/mbproto.h
@@ -45,24 +45,29 @@ PR_BEGIN_EXTERN_C
 #define MB_ADDRESS_BROADCAST    ( 0 )   /*! Modbus broadcast address. */
 #define MB_ADDRESS_MIN          ( 1 )   /*! Smallest possible slave address. */
 #define MB_ADDRESS_MAX          ( 247 ) /*! Biggest possible slave address. */
-#define MB_FUNC_NONE                          (  0 )
-#define MB_FUNC_READ_COILS                    (  1 )
-#define MB_FUNC_READ_DISCRETE_INPUTS          (  2 )
-#define MB_FUNC_WRITE_SINGLE_COIL             (  5 )
-#define MB_FUNC_WRITE_MULTIPLE_COILS          ( 15 )
-#define MB_FUNC_READ_HOLDING_REGISTER         (  3 )
-#define MB_FUNC_READ_INPUT_REGISTER           (  4 )
-#define MB_FUNC_WRITE_REGISTER                (  6 )
-#define MB_FUNC_WRITE_MULTIPLE_REGISTERS      ( 16 )
-#define MB_FUNC_READWRITE_MULTIPLE_REGISTERS  ( 23 )
-#define MB_FUNC_DIAG_READ_EXCEPTION           (  7 )
-#define MB_FUNC_DIAG_DIAGNOSTIC               (  8 )
-#define MB_FUNC_DIAG_GET_COM_EVENT_CNT        ( 11 )
-#define MB_FUNC_DIAG_GET_COM_EVENT_LOG        ( 12 )
-#define MB_FUNC_OTHER_REPORT_SLAVEID          ( 17 )
-#define MB_FUNC_ERROR                         ( 128u )
+
+typedef enum eMbCommands_t
+{
+    MB_FUNC_NONE =                        (  0 ),
+    MB_FUNC_READ_COILS =                  (  1 ),
+    MB_FUNC_READ_DISCRETE_INPUTS =        (  2 ),
+    MB_FUNC_WRITE_SINGLE_COIL =           (  5 ),
+    MB_FUNC_WRITE_MULTIPLE_COILS =        ( 15 ),
+    MB_FUNC_READ_HOLDING_REGISTER =       (  3 ),
+    MB_FUNC_READ_INPUT_REGISTER =         (  4 ),
+    MB_FUNC_WRITE_REGISTER =              (  6 ),
+    MB_FUNC_WRITE_MULTIPLE_REGISTERS =    ( 16 ),
+    MB_FUNC_READWRITE_MULTIPLE_REGISTERS =( 23 ),
+    MB_FUNC_DIAG_READ_EXCEPTION =         (  7 ),
+    MB_FUNC_DIAG_DIAGNOSTIC =             (  8 ),
+    MB_FUNC_DIAG_GET_COM_EVENT_CNT =      ( 11 ),
+    MB_FUNC_DIAG_GET_COM_EVENT_LOG =      ( 12 ),
+    MB_FUNC_OTHER_REPORT_SLAVEID =        ( 17 ),
+    MB_FUNC_ERROR =                       ( 128u )
+} eMBCommands;
+
 /* ----------------------- Type definitions ---------------------------------*/
-    typedef enum
+typedef enum
 {
     MB_EX_NONE = 0x00,
     MB_EX_ILLEGAL_FUNCTION = 0x01,