A very slender config just for test builds.

ROMFS/px4fmu_test/init.d/rc.standalone

+#!nsh
+#
+# Flight startup script for PX4FMU standalone configuration.
+#
+
+echo "[init] doing standalone PX4FMU startup..."
+
+#
+# Start the ORB
+#
+uorb start
+
+echo "[init] startup done"

ROMFS/px4fmu_test/init.d/rcS

+#!nsh
+#
+# PX4FMU startup script for test hackery.
+#

makefiles/config_px4fmuv2_test.mk

+#
+# Makefile for the px4fmu_default configuration
+#
+
+#
+# Use the configuration's ROMFS.
+#
+ROMFS_ROOT	 = $(PX4_BASE)/ROMFS/px4fmu_test
+
+#
+# Board support modules
+#
+MODULES		+= drivers/device
+MODULES		+= drivers/stm32
+MODULES		+= drivers/px4io
+MODULES		+= drivers/boards/px4fmuv2
+MODULES		+= systemcmds/perf
+MODULES		+= systemcmds/reboot
+
+# needed because things use it for logging
+MODULES		+= modules/mavlink
+
+#
+# Library modules
+#
+MODULES		+= modules/systemlib
+MODULES		+= modules/systemlib/mixer
+MODULES		+= modules/uORB
+
+#
+# Transitional support - add commands from the NuttX export archive.
+#
+# In general, these should move to modules over time.
+#
+# Each entry here is <command>.<priority>.<stacksize>.<entrypoint> but we use a helper macro
+# to make the table a bit more readable.
+#
+define _B
+	$(strip $1).$(or $(strip $2),SCHED_PRIORITY_DEFAULT).$(or $(strip $3),CONFIG_PTHREAD_STACK_DEFAULT).$(strip $4)
+endef
+
+#                  command                 priority                   stack  entrypoint
+BUILTIN_COMMANDS := \
+	$(call _B, sercon,                 ,                          2048,  sercon_main                ) \
+	$(call _B, serdis,                 ,                          2048,  serdis_main                )