diff --git a/src/bacnet/basic/object/ai.c b/src/bacnet/basic/object/ai.c
index 43d37580..60b31d7f 100644
--- a/src/bacnet/basic/object/ai.c
+++ b/src/bacnet/basic/object/ai.c
@@ -1,31 +1,16 @@
-/**************************************************************************
+/**
+ * @file
+ * @brief Analog Input Objects - customize for your use
+ * @author Steve Karg <skarg@users.sourceforge.net>
+ * @author Krzysztof Malorny <malornykrzysztof@gmail.com>
+ * @date 2005
+ * @section LICENSE
  *
  * Copyright (C) 2005 Steve Karg <skarg@users.sourceforge.net>
  * Copyright (C) 2011 Krzysztof Malorny <malornykrzysztof@gmail.com>
  *
- * Permission is hereby granted, free of charge, to any person obtaining
- * a copy of this software and associated documentation files (the
- * "Software"), to deal in the Software without restriction, including
- * without limitation the rights to use, copy, modify, merge, publish,
- * distribute, sublicense, and/or sell copies of the Software, and to
- * permit persons to whom the Software is furnished to do so, subject to
- * the following conditions:
- *
- * The above copyright notice and this permission notice shall be included
- * in all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
- * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
- * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
- * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
- * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
- * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- *
- *********************************************************************/
-
-/* Analog Input Objects customize for your use */
-
+ * SPDX-License-Identifier: MIT
+ */
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -250,12 +235,14 @@ void Analog_Input_Present_Value_Set(uint32_t object_instance, float value)
 bool Analog_Input_Object_Name(
     uint32_t object_instance, BACNET_CHARACTER_STRING *object_name)
 {
+    unsigned int index = 0;
     static char text_string[32] = "";
     bool status = false;
 
-    if (object_instance < MAX_ANALOG_INPUTS) {
-        if (AI_Descr[object_instance].Object_Name) {
-            status = characterstring_init_ansi(object_name, AI_Descr[object_instance].Object_Name);
+    index = Analog_Input_Instance_To_Index(object_instance);
+    if (index < MAX_ANALOG_INPUTS) {
+        if (AI_Descr[index].Object_Name) {
+            status = characterstring_init_ansi(object_name, AI_Descr[index].Object_Name);
         } else {
             snprintf(text_string, sizeof(text_string), "ANALOG INPUT %u",
                 object_instance);
@@ -276,10 +263,13 @@ bool Analog_Input_Object_Name(
  */
 bool Analog_Input_Name_Set(uint32_t object_instance, char *new_name)
 {
+    unsigned int index = 0;
     bool status = false;
-    if (object_instance < MAX_ANALOG_INPUTS) {
+
+    index = Analog_Input_Instance_To_Index(object_instance);
+    if (index < MAX_ANALOG_INPUTS) {
         status = true;
-        AI_Descr[object_instance].Object_Name = new_name;
+        AI_Descr[index].Object_Name = new_name;
     }
 
     return status;
@@ -317,9 +307,11 @@ unsigned Analog_Input_Event_State(uint32_t object_instance)
 char *Analog_Input_Description(uint32_t object_instance)
 {
     char *name = NULL;
+    unsigned index = 0;
 
-    if (object_instance < MAX_ANALOG_INPUTS) {
-        name = AI_Descr[object_instance].Description;
+    index = Analog_Input_Instance_To_Index(object_instance);
+    if (index < MAX_ANALOG_INPUTS) {
+        name = AI_Descr[index].Description;
     }
 
     return name;
@@ -334,10 +326,12 @@ char *Analog_Input_Description(uint32_t object_instance)
 bool Analog_Input_Description_Set(uint32_t object_instance, char *new_name)
 {
     bool status = false; /* return value */
+    unsigned index = 0;
 
-    if (object_instance < MAX_ANALOG_INPUTS && new_name) {
+    index = Analog_Input_Instance_To_Index(object_instance);
+    if (index < MAX_ANALOG_INPUTS && new_name) {
+        AI_Descr[index].Description = new_name;
         status = true;
-        AI_Descr[object_instance].Description = new_name;
     }
 
     return status;
@@ -433,9 +427,11 @@ void Analog_Input_COV_Increment_Set(uint32_t object_instance, float value)
 uint16_t Analog_Input_Units(uint32_t object_instance)
 {
     uint16_t units = UNITS_NO_UNITS;
+    unsigned index = 0;
 
-    if (object_instance < MAX_ANALOG_INPUTS) {
-        units = AI_Descr[object_instance].Units;
+    index = Analog_Input_Instance_To_Index(object_instance);
+    if (index < MAX_ANALOG_INPUTS) {
+        units = AI_Descr[index].Units;
     }
 
     return units;
@@ -452,9 +448,11 @@ uint16_t Analog_Input_Units(uint32_t object_instance)
 bool Analog_Input_Units_Set(uint32_t object_instance, uint16_t units)
 {
     bool status = false;
+    unsigned index = 0;
 
-    if (object_instance < MAX_ANALOG_INPUTS) {
-        AI_Descr[object_instance].Units = units;
+    index = Analog_Input_Instance_To_Index(object_instance);
+    if (index < MAX_ANALOG_INPUTS) {
+        AI_Descr[index].Units = units;
         status = true;
     }