Unable to open serial port, another device might be using COM1. Run chgport /query. If the built-in Windows serial driver on the VDA is auto-assigning Device Serial0 to a COM1 port of your VDA, do the following: A. Open CMD on the VDA and type NET USE. Delete any existing mapping (for example, COM1) on the VDA. NET USE COM1 /DELETE. The KMDF driver for a peripheral device on a SerCx2-managed serial port requires certain hardware resources to operate the device. Included in these resources is the information that the driver needs to open a logical connection to the serial port. The serial port ttySx (x=0,1,2, etc.) is major number 4. You can see this (and the minor numbers too) by typing: 'ls -l ttyS.' in the /dev directory. To find the device names for various devices, see the 'devices' file in the kernel documentation. There formerly was a 'cua' name for each serial port and it behaved just a little differently. To install a legacy COM port, you must set a legacy COM port subkey for the device under this key. The COM port subkey contains the registry settings for a legacy COM port. When Serial is loaded it determines which legacy ports were not previously detected by checking the LegacyDiscovered entry value for a legacy port.
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The Serial function driver always configures a legacy serial port as a COM port.
Serial detects the presence of legacy ports by reading corresponding COM port subkeys under the ..ServicesSerialParameters key. To install a legacy COM port, you must set a legacy COM port subkey for the device under this key. The COM port subkey contains the registry settings for a legacy COM port.
When Serial is loaded it determines which legacy ports were not previously detected by checking the LegacyDiscovered entry value for a legacy port. If this entry value does not exist or is zero, Serial performs the following tasks:
Calls IoReportDetectedDevice to report the device to the Plug and Play manager.
Sets the LegacyDiscovered entry value for the port to 0x00000001, which indicates that the port has been reported.
Copies some of the entry values under the COM port subkey to the Plug and Play device key for the physical device object (PDO) that is returned by IoReportDetectedDevice.
Serial sets the PortName entry value under the Plug and Play device key to the value of the DosDevices entry value under the legacy COM port subkey. For all other entry values that Serial copies, it retains the same entry value name. For more information about which entry values that Serial copies, see the Serial sample code provided in the Microsoft Windows Driver Kit (WDK).
The IoReportDetectedDevice call marks the port as a root-enumerated device. On subsequent system boots, the Plug and Play manager automatically configures the device based on the information in its INF file.
Serial Com Device Port Devices Drivers
The Plug and Play manager creates the following compatible IDs for a legacy COM port: DETECTEDInternalSerial and DETECTEDSerial.