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6.3 Troubleshooting of composite connections
6.3 Troubleshooting of composite connections
The firmware used by the autopilot with F7 or H7 processor and CAN interface provides two USB interfaces. One for the normal MAVLink connection and one for the SLCAN serial connection to the CAN interface for configuration and firmware updates. This is called a composite USB device.
By default, MAVLink 's USB port is SERIAL0 , while SLCAN 's USB port is the highest SERIALx port on the board. The Windows driver currently installed with the Mission Planner can choose to use one of them, since the MAVLINK protocol is set by default in the ArduPilot firmware, no matter which one is selected as the COM port, it will work normally.
However, there is one case where the user will find that it cannot connect to the COM port that is evident in the Mission Planner drop-down box . This happens when the user accidentally changes the protocol of any SERIALx port that Windows drives as a MAVLink COM port to a protocol other than MAVLink . This can easily happen if the user takes an existing parameter file from a different autopilot used aircraft configuration and the protocol of that file has changed. For example, a user owns an aircraft with a non- F7/H7 CAN autopilot , upgrades it to one with that capability, and then loads his existing parameter file when setting up the aircraft with the new autopilot . Once the parameter file is loaded and the autopilot is restarted, communication is lost and cannot be re-established.
What happens is that the protocol of the SERIALx port used by Windows has been changed. Almost always, this is the highest numbered SERIALx port, since on non- CAN capable autopilots this is usually set to -1 , and Windows ' COM port driver chooses that interface as the COM port instead of SERIAL0 .
The recovery steps are as follows:
- Go into Windows Device Manager and find the COM port the autopilot is using in the port list . It will have the COM port # you originally used to connect to the Mission Planner . Right click and it will show " Update Driver Software " as one of the options. click it;
- Click the " Browse my computer... " option, then the " Choose from a list... " option and you'll see this screen:
- Scroll down the list until the " Composite USB " option appears and tap it;
- Now reconnect your autopilot to the computer and two COM ports will appear. One will connect (the remaining one has MAVLink protocol), the other will not. If you don't connect to one, try the other. But do not disconnect the autopilot from the computer, otherwise the composite driver will uninstall and you will have to start over;
- Now that you are connected to Mission Planner , change the protocol of the Serialx port back to 2 ( MAVLink2 ). Now you can disconnect and reconnect the autopilot and it will only show a COM port, from now on you should be able to connect. Do not change this protocol from now on, unless trying to utilize the SLCAN interface. It may be a bit unfamiliar since the Mission Planner SERIALx port is no longer the normal SERIAL0 , but the highest port, but this does not affect autopilot configuration and operation.