The beginning of doxygenation:

As a first step, added an @file description for each file.

bacnet-stack/demo/server/Makefile

@@ -9,7 +9,7 @@ TARGET = bacserv
 #BACDL_DEFINE = -DBACDL_ETHERNET
 #BACDL_DEFINE = -DBACDL_ARCNET
 #BACDL_DEFINE = -DBACDL_MSTP
-BACDL_DEFINE = -DBACDL_BIP -DBIP_DEBUG
+BACDL_DEFINE = -DBACDL_BIP
 BACNET_DEFINES = -DPRINT_ENABLED=1 -DBACAPP_ALL -DBACFILE
 DEFINES = $(BACNET_DEFINES) $(BACDL_DEFINE)
 
@@ -41,6 +41,9 @@ OPTIMIZATION = -Os
 ifeq (${BUILD},debug)
 OPTIMIZATION = -O0
 DEBUGGING = -g
+ifeq (${BACDL_DEFINE},-DBACDL_BIP=1)
+DEFINES += -DBIP_DEBUG
+endif
 endif
 # put all the flags together
 CFLAGS = -Wall $(DEBUGGING) $(OPTIMIZATION) $(INCLUDES) $(DEFINES) -fdata-sections -ffunction-sections

bacnet-stack/demo/server/main.c

@@ -50,7 +50,7 @@
 /* include the device object */
 #include "device.h"
 
-/* This is an example server application using the BACnet Stack */
+/** @file server/main.c  Example server application using the BACnet Stack */
 
 /* buffers used for receiving */
 static uint8_t Rx_Buf[MAX_MPDU] = { 0 };