mavlink USB auto start/stop on boards with VBUS

 - no longer start sercon or mavlink usb by default
 - on USB connection (VBUS) monitor serial USB at low rate and start Mavlink if there's a HEARTBEAT or nshterm on 3 consecutive carriage returns
 - the mavlink USB instance is automatically stopped and serdis executed if USB is disconnected
 - skipping Mavlink USB (and sercon) saves a considerable amount of memory on older boards

.ci/Jenkinsfile-hardware

@@ -867,8 +867,8 @@ void checkStatus() {
   sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "ls /etc"'
   sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "ls /obj"'
   sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "ls /proc"'
-  sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "mavlink status streams"'
-  sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "mavlink status"'
+  sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "mavlink status streams" || true'
+  sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "mavlink status" || true'
   sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "mount"'
   sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "mtd status"'
   sh './Tools/HIL/run_nsh_cmd.py --device `find /dev/serial -name *usb-*` --cmd "param show" || true'

ROMFS/cannode/init.d/rcS

@@ -16,11 +16,6 @@ set +e
 #------------------------------------------------------------------------------
 set R /
 
-#
-# Start CDC/ACM serial driver.
-#
-sercon
-
 #
 # Print full system version.
 #

ROMFS/px4fmu_common/init.d/rcS

@@ -49,11 +49,6 @@ set STARTUP_TUNE 1
 set USE_IO no
 set VEHICLE_TYPE none
 
-#
-# Start CDC/ACM serial driver.
-#
-sercon
-
 #
 # Print full system version.
 #

ROMFS/px4fmu_test/init.d/rcS

@@ -13,14 +13,6 @@ then
 	led_control on -c blue
 fi
 
-if sercon
-then
-	echo "[i] USB interface connected"
-
-	# Try to get an USB console
-	nshterm /dev/ttyACM0 &
-fi
-
 #
 # Try to mount the microSD card.
 #

Tools/mavlink_shell.py

@@ -45,6 +45,7 @@ def __init__(self, portname, baudrate, devnum=0, debug=0):
         self.port = devnum
         self.debug("Connecting with MAVLink to %s ..." % portname)
         self.mav = mavutil.mavlink_connection(portname, autoreconnect=True, baud=baudrate)
+        self.mav.mav.heartbeat_send(mavutil.mavlink.MAV_TYPE_GENERIC, mavutil.mavlink.MAV_AUTOPILOT_INVALID, 0, 0, 0)
         self.mav.wait_heartbeat()
         self.debug("HEARTBEAT OK\n")
         self.debug("Locked serial device\n")
@@ -226,8 +227,7 @@ def erase_last_n_chars(N):
             # handle heartbeat sending
             heartbeat_time = timer()
             if heartbeat_time > next_heartbeat_time:
-                mav_serialport.mav.mav.heartbeat_send(mavutil.mavlink.MAV_TYPE_GCS,
-                        mavutil.mavlink.MAV_AUTOPILOT_GENERIC, 0, 0, 0)
+                mav_serialport.mav.mav.heartbeat_send(mavutil.mavlink.MAV_TYPE_GENERIC, mavutil.mavlink.MAV_AUTOPILOT_INVALID, 0, 0, 0)
                 next_heartbeat_time = heartbeat_time + 1
 
     except serial.serialutil.SerialException as e:

boards/atl/mantis-edu/init/rc.board_mavlink

@@ -14,6 +14,3 @@ mavlink stream -d ${GIMBAL_TTY} -s GIMBAL_DEVICE_SET_ATTITUDE -r 20
 
 # optical flow
 mavlink start -d /dev/ttyS2 -m custom -b 500000
-
-# Start MAVLink on the USB port
-mavlink start -d /dev/ttyACM0

boards/cubepilot/cubeorange/init/rc.board_mavlink

@@ -3,9 +3,6 @@
 # Board specific MAVLink startup script.
 #------------------------------------------------------------------------------
 
-# Start MAVLink on the USB port
-mavlink start -d /dev/ttyACM0
-
 # Start ADS-B receiver mavlink connection if console not present
 if [ ! -e /dev/console ]
 then