diff --git a/libraries/AP_HAL_PX4/scripts/rc.APM b/libraries/AP_HAL_PX4/scripts/rc.APM
index dc89929d7a..1bd7e0957c 100644
--- a/libraries/AP_HAL_PX4/scripts/rc.APM
+++ b/libraries/AP_HAL_PX4/scripts/rc.APM
@@ -2,17 +2,26 @@
 
 # APM startup script for NuttX on PX4
 
+# To disable APM startup add a /fs/microsd/APM/nostart file
+# To disable use of a PX4IO board add a file /fs/microsd/APM/fmu_only
+
+set deviceA /dev/ttyACM0
+set deviceC /dev/ttyS1
+
 if [ -f /fs/microsd/APM/nostart ]
 then
    echo "APM/nostart found - skipping"
 else
 
-uorb start
-
 # mount binfs so we can find the built-in apps
-mount -t binfs /dev/null /bin
+if [ -f /bin/reboot ]
+then
+	echo "binfs already mounted"
+else
+	echo "Mounting binfs"
+	mount -t binfs /dev/null /bin
+fi
 
-set device /dev/ttyS1
 set sketch NONE
 
 if [ -f /bin/ArduPlane ]
@@ -32,40 +41,59 @@ fi
 
 if [ $sketch != NONE ]
 then
+	if [ -f /fs/microsd/px4io.bin ]
+	then
+	   echo "Checking for new px4io firmware"
+	   if cmp /fs/microsd/px4io.bin /fs/microsd/px4io.bin.loaded
+	   then
+	      echo "No new px4io firmware"
+	   else
+	      echo "Loading /fs/microsd/px4io.bin"
+	      px4io update /fs/microsd/px4io.bin > /fs/microsd/APM/px4io_update.log
+	      cp /fs/microsd/px4io.bin /fs/microsd/px4io.bin.loaded
+	      echo "Loaded /fs/microsd/px4io.bin OK" >> /fs/microsd/APM/px4io_update.log
+	   fi
+	fi
+
 	echo "Starting APM sensors"
+	uorb start
 	mpu6000 start
 	ms5611 start
 	hmc5883 start
 	adc start
 
-	echo Trying PX4IO start
-	if px4io start
+	if [ -f /fs/microsd/APM/fmu_only ]
 	then
-		echo Setting up PX4IO board
-		echo Loading FMU_pass mixer
-		mixer load /dev/pwm_output /etc/mixers/FMU_pass.mix
-		echo Setting FMU mode_serial
-		fmu mode_serial
-	else
-		echo Setting up PX4FMU direct mode
+		echo "Setting up PX4FMU direct mode"
 		fmu start mode_pwm
-		if [ $device == /dev/ttyS1 ]
+		if [ $deviceC == /dev/ttyS1 ]
 		then
 			# ttyS1 is used for PWM output when there
 			# is no IO board
-			set device /dev/ttyS2
+			set deviceC /dev/ttyS2
 		fi
+	else
+		echo "Setting up PX4IO board"
+		px4io start
+		echo "Loading FMU_pass mixer"
+		mixer load /dev/pwm_output /etc/mixers/FMU_pass.mix
+		echo "Setting FMU mode_serial"
+		fmu mode_serial
 	fi
+
 	echo Starting $sketch
-	$sketch -d $device start
+	$sketch -d $deviceA -d2 $deviceC start
 
 	# if starting on the console, tell nsh to exit
 	# this prevents it from chewing bytes
-	if [ $device == /dev/ttyS0 ]
+	if [ $deviceC == /dev/ttyS0 ]
 	then
+		echo "Exiting from nsh shell"
 		exit
 	fi
 else
 	echo "No APM sketch found"
 fi
 fi
+
+echo "rc.APM finished"