Index: firmware/App/Modes/ModeService.c
===================================================================
diff -u -r499e5de29e706d09f79ba22511068990c4044e84 -rc48a99d2d1c852adcc986253b6c420a90dab7bfe
--- firmware/App/Modes/ModeService.c	(.../ModeService.c)	(revision 499e5de29e706d09f79ba22511068990c4044e84)
+++ firmware/App/Modes/ModeService.c	(.../ModeService.c)	(revision c48a99d2d1c852adcc986253b6c420a90dab7bfe)
@@ -1,4 +1,4 @@
-/**************************************************************************
+/*********************************************************************//***
  *
  *  Copyright (c) 2019-2020 Diality Inc. - All Rights Reserved.
  *
@@ -17,46 +17,72 @@
 #include "OperationModes.h"
 #include "ModeService.h"
 
+/**
+ *  @addtogroup ServiceMode
+ *  @{
+ */
+
+// ********** private definitions **********
+
+/// Enumeration of service mode states.
+typedef enum Service_States
+{
+    SERVICE_STATE_START = 0,                                     ///< Start service mode state.
+    NUM_OF_SERVICE_STATES                                        ///< Number of service mode states.
+} SERVICE_STATE_T;
+
 // ********** private data **********
 
+static SERVICE_STATE_T serviceState = SERVICE_STATE_START;       ///< Currently active service state.
+
 // ********** private function prototypes **********
 
-/*************************************************************************
- * @brief initServiceMode
+/*********************************************************************//**
+ * @brief
  * The initServiceMode function initializes the Service Mode module.
  * @details
  * Inputs : none
  * Outputs : Service Mode module initialized.
- * @param none
  * @return none
  *************************************************************************/
 void initServiceMode( void )
 {
+    serviceState = SERVICE_STATE_START;
 }
 
-/*************************************************************************
- * @brief transitionToServiceMode
+/*********************************************************************//**
+ * @brief
  * The transitionToServiceMode function prepares for transition to service mode.
  * @details
  * Inputs : none
  * Outputs :
- * @param none
  * @return none
  *************************************************************************/
 void transitionToServiceMode( void )
 {
 }
 
-/*************************************************************************
- * @brief execServiceMode
+/*********************************************************************//**
+ * @brief
  * The execServiceMode function executes the Service Mode state machine.
  * @details
  * Inputs : none
  * Outputs :
- * @param none
  * @return none
  *************************************************************************/
 void execServiceMode( void )
 {
+    // execute current service state
+    switch ( serviceState )
+    {
+        case SERVICE_STATE_START:
+            break;
+
+        default:
+            serviceState = SERVICE_STATE_START;
+            // TODO - s/w fault
+            break;
+    }
 }
 
+/**@}*/