diff --git a/Makefile.include b/Makefile.include
index 83f673cb0..5f3008244 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -377,6 +377,9 @@ viewconf:
 	@echo "----------------- C variables: -----------------"
 	$(Q)$(CC) $(CFLAGS) -E $(CONTIKI)/tools/viewconf.c | grep \#\#\#\#\#
 	@echo "------------------------------------------------"
+	@echo "'==' Means the flag is set to a given a value"
+	@echo "'->' Means the flag is unset, but will default to a given value"
+	@echo "'><' Means the flag is unset and has no default value"
 	@echo "To view more Make variables, edit $(CONTIKI)/Makefile.include, rule 'viewconf'"
 	@echo "To view more C variables, edit $(CONTIKI)/tools/viewconf.c"
 
diff --git a/tools/viewconf.c b/tools/viewconf.c
index 749cf436f..3974cf4dc 100644
--- a/tools/viewconf.c
+++ b/tools/viewconf.c
@@ -9,39 +9,141 @@
 #include "os/net/nbr-table.h"
 #include "os/sys/log-conf.h"
 
-##### "PROJECT_CONF_PATH": _____________________ PROJECT_CONF_PATH
-##### "CONTIKI_VERSION_STRING": ________________ CONTIKI_VERSION_STRING
-##### "IEEE802154_PANID":_______________________ IEEE802154_PANID
-##### "FRAME802154_VERSION":____________________ FRAME802154_VERSION
+#ifdef PROJECT_CONF_PATH
+##### "PROJECT_CONF_PATH": _____________________ == PROJECT_CONF_PATH
+#else
+##### "PROJECT_CONF_PATH": _____________________ ><
+#endif
+
+##### "CONTIKI_VERSION_STRING": ________________ == CONTIKI_VERSION_STRING
+
+#ifdef IEEE802154_CONF_PANID
+##### "IEEE802154_CONF_PANID":__________________ == IEEE802154_CONF_PANID
+#else
+##### "IEEE802154_CONF_PANID":__________________ == IEEE802154_PANID
+#endif
+
+#ifdef FRAME802154_CONF_VERSION
+##### "FRAME802154_CONF_VERSION":_______________ == FRAME802154_CONF_VERSION
+#else
+##### "FRAME802154_CONF_VERSION":_______________ == FRAME802154_VERSION
+#endif
+
 #if MAC_CONF_WITH_TSCH
-##### "TSCH_DEFAULT_HOPPING_SEQUENCE": _________ TSCH_DEFAULT_HOPPING_SEQUENCE
-##### "TSCH_JOIN_HOPPING_SEQUENCE": ____________ TSCH_JOIN_HOPPING_SEQUENCE
-##### "TSCH_EB_PERIOD": ________________________ TSCH_EB_PERIOD
-##### "TSCH_MAX_EB_PERIOD": ____________________ TSCH_MAX_EB_PERIOD
-##### "TSCH_CONF_DEFAULT_TIMESLOT_LENGTH": _____ TSCH_CONF_DEFAULT_TIMESLOT_LENGTH
-##### "TSCH_SCHEDULE_DEFAULT_LENGTH": __________ TSCH_SCHEDULE_DEFAULT_LENGTH
+
+#ifdef TSCH_CONF_DEFAULT_HOPPING_SEQUENCE
+##### "TSCH_CONF_DEFAULT_HOPPING_SEQUENCE": ____ == TTSCH_CONF_DEFAULT_HOPPING_SEQUENCE
+#else
+##### "TSCH_CONF_DEFAULT_HOPPING_SEQUENCE": ____ -> TSCH_DEFAULT_HOPPING_SEQUENCE
+#endif
+
+#ifdef TSCH_CONF_JOIN_HOPPING_SEQUENCE
+##### "TSCH_CONF_JOIN_HOPPING_SEQUENCE": _______ == TSCH_CONF_JOIN_HOPPING_SEQUENCE
+#else
+##### "TSCH_CONF_JOIN_HOPPING_SEQUENCE": _______ -> TSCH_JOIN_HOPPING_SEQUENCE
+#endif
+
+#ifdef TSCH_CONF_EB_PERIOD
+##### "TSCH_CONF_EB_PERIOD": ___________________ == TSCH_CONF_EB_PERIOD
+#else
+##### "TSCH_CONF_EB_PERIOD": ___________________ -> TSCH_EB_PERIOD
+#endif
+
+#ifdef TSCH_CONF_MAX_EB_PERIOD
+##### "TSCH_CONF_MAX_EB_PERIOD": _______________ == TSCH_CONF_MAX_EB_PERIOD
+#else
+##### "TSCH_CONF_MAX_EB_PERIOD": _______________ -> TSCH_MAX_EB_PERIOD
+#endif
+
+#if TSCH_CONF_DEFAULT_TIMESLOT_LENGTH
+##### "TSCH_CONF_DEFAULT_TIMESLOT_LENGTH": _____ == TSCH_CONF_DEFAULT_TIMESLOT_LENGTH
+#else
+##### "TSCH_CONF_DEFAULT_TIMESLOT_LENGTH": _____ -> TSCH_DEFAULT_TIMESLOT_LENGTH
+#endif
+
+#ifdef TSCH_CONF_SCHEDULE_DEFAULT_LENGTH
+##### "TSCH_CONF_SCHEDULE_DEFAULT_LENGTH": _____ == TSCH_CONF_SCHEDULE_DEFAULT_LENGTH
+#else
+##### "TSCH_CONF_SCHEDULE_DEFAULT_LENGTH": _____ -> TSCH_CHEDULE_DEFAULT_LENGTH
+#endif
+
 #else /* MAC_CONF_WITH_TSCH */
-##### "RF_CHANNEL": ____________________________ RF_CHANNEL
+
+#ifdef RF_CHANNEL
+##### "RF_CHANNEL": ____________________________ == RF_CHANNEL
+#else
+##### "RF_CHANNEL": ____________________________ ><
+#endif
+
 #endif /*MAC_CONF_WITH_TSCH */
-##### "QUEUEBUF_NUM": __________________________ QUEUEBUF_NUM
-##### "NBR_TABLE_MAX_NEIGHBORS": _______________ NBR_TABLE_MAX_NEIGHBORS
-##### "NETSTACK_MAX_ROUTE_ENTRIES": ____________ NETSTACK_MAX_ROUTE_ENTRIES
-##### "UIP_CONF_BUFFER_SIZE": __________________ UIP_CONF_BUFFER_SIZE
-##### "UIP_CONF_UDP": __________________________ UIP_CONF_UDP
-##### "UIP_UDP_CONNS": _________________________ UIP_UDP_CONNS
-##### "UIP_CONF_TCP": __________________________ UIP_CONF_TCP
-##### "UIP_TCP_CONNS": _________________________ UIP_TCP_CONNS
-##### "UIP_ND6_SEND_RA": _______________________ UIP_ND6_SEND_RA
-##### "UIP_ND6_SEND_NS": _______________________ UIP_ND6_SEND_NS
-##### "UIP_ND6_SEND_NA": _______________________ UIP_ND6_SEND_NA
-##### "UIP_ND6_AUTOFILL_NBR_CACHE": ____________ UIP_ND6_AUTOFILL_NBR_CACHE
-##### "SICSLOWPAN_CONF_FRAG": __________________ SICSLOWPAN_CONF_FRAG
-##### "SICSLOWPAN_COMPRESSION": ________________ SICSLOWPAN_COMPRESSION
-##### "LOG_CONF_LEVEL_RPL": ____________________ LOG_CONF_LEVEL_RPL
-##### "LOG_CONF_LEVEL_TCPIP": __________________ LOG_CONF_LEVEL_TCPIP
-##### "LOG_CONF_LEVEL_IPV6": ___________________ LOG_CONF_LEVEL_IPV6
-##### "LOG_CONF_LEVEL_6LOWPAN": ________________ LOG_CONF_LEVEL_6LOWPAN
-##### "LOG_CONF_LEVEL_NULLNET": ________________ LOG_CONF_LEVEL_NULLNET
-##### "LOG_CONF_LEVEL_MAC": ____________________ LOG_CONF_LEVEL_MAC
-##### "LOG_CONF_LEVEL_FRAMER": _________________ LOG_CONF_LEVEL_FRAMER
-##### "LOG_CONF_LEVEL_6TOP": ___________________ LOG_CONF_LEVEL_6TOP
+
+#ifdef QUEUEBUF_CONF_NUM
+##### "QUEUEBUF_CONF_NUM": _____________________ == QUEUEBUF_CONF_NUM
+#else
+##### "QUEUEBUF_CONF_NUM": _____________________ -> QUEUEBUF_NUM
+#endif
+
+#ifdef NBR_TABLE_CONF_MAX_NEIGHBORS
+##### "NBR_TABLE_CONF_MAX_NEIGHBORS": __________ == NBR_TABLE_CONF_MAX_NEIGHBORS
+#else
+##### "NBR_TABLE_CONF_MAX_NEIGHBORS": __________ -> NBR_TABLE_MAX_NEIGHBORS
+#endif
+
+##### "NETSTACK_MAX_ROUTE_ENTRIES": ____________ == NETSTACK_MAX_ROUTE_ENTRIES
+##### "UIP_CONF_BUFFER_SIZE": __________________ == UIP_CONF_BUFFER_SIZE
+##### "UIP_CONF_UDP": __________________________ == UIP_CONF_UDP
+
+#ifdef UIP_CONF_UDP_CONNS
+##### "UIP_CONF_UDP_CONNS": ____________________ == UIP_CONF_UDP_CONNS
+#else
+##### "UIP_CONF_UDP_CONNS": ____________________ -> UIP_UDP_CONNS
+#endif
+
+##### "UIP_CONF_TCP": __________________________ == UIP_CONF_TCP
+
+#ifdef UIP_CONF_TCP_CONNS
+##### "UIP_CONF_TCP_CONNS": ____________________ == UIP_CONF_TCP_CONNS
+#else
+##### "UIP_CONF_TCP_CONNS": ____________________ -> UIP_TCP_CONNS
+#endif
+
+#ifdef UIP_CONF_ND6_SEND_RA
+##### "UIP_CONF_ND6_SEND_RA": __________________ == UIP_CONF_ND6_SEND_RA
+#else
+##### "UIP_CONF_ND6_SEND_RA": __________________ -> UIP_ND6_SEND_RA
+#endif
+
+#ifdef UIP_CONF_ND6_SEND_NS
+##### "UIP_CONF_ND6_SEND_NS": __________________ == UIP_CONF_ND6_SEND_NS
+#else
+##### "UIP_CONF_ND6_SEND_NS": __________________ -> UIP_ND6_SEND_NS
+#endif
+
+#ifdef UIP_CONF_ND6_SEND_NA
+##### "UIP_CONF_ND6_SEND_NA": __________________ == UIP_CONF_ND6_SEND_NA
+#else
+##### "UIP_CONF_ND6_SEND_NA": __________________ -> UIP_ND6_SEND_NA
+#endif
+
+#ifdef UIP_CONF_ND6_AUTOFILL_NBR_CACHE
+##### "UIP_CONF_ND6_AUTOFILL_NBR_CACHE": _______ == UIP_CONF_ND6_AUTOFILL_NBR_CACHE
+#else
+##### "UIP_CONF_ND6_AUTOFILL_NBR_CACHE": _______ -> UIP_ND6_AUTOFILL_NBR_CACHE
+#endif
+
+##### "SICSLOWPAN_CONF_FRAG": __________________ == SICSLOWPAN_CONF_FRAG
+
+#ifdef SICSLOWPAN_CONF_COMPRESSION
+##### "SICSLOWPAN_CONF_COMPRESSION": ___________ == SICSLOWPAN_CONF_COMPRESSION
+#else
+##### "SICSLOWPAN_CONF_COMPRESSION": ___________ -> SICSLOWPAN_COMPRESSION
+#endif
+
+##### "LOG_CONF_LEVEL_RPL": ____________________ == LOG_CONF_LEVEL_RPL
+##### "LOG_CONF_LEVEL_TCPIP": __________________ == LOG_CONF_LEVEL_TCPIP
+##### "LOG_CONF_LEVEL_IPV6": ___________________ == LOG_CONF_LEVEL_IPV6
+##### "LOG_CONF_LEVEL_6LOWPAN": ________________ == LOG_CONF_LEVEL_6LOWPAN
+##### "LOG_CONF_LEVEL_NULLNET": ________________ == LOG_CONF_LEVEL_NULLNET
+##### "LOG_CONF_LEVEL_MAC": ____________________ == LOG_CONF_LEVEL_MAC
+##### "LOG_CONF_LEVEL_FRAMER": _________________ == LOG_CONF_LEVEL_FRAMER
+##### "LOG_CONF_LEVEL_6TOP": ___________________ == LOG_CONF_LEVEL_6TOP