Dec 21, 2020 • Filed to: USB Recovery • Proven solutions

Have you ever had difficulty connecting your devices to your computer using a Prolific USB to Serial adapter? If yes you are lucky to find this page, it will give you all the information need to fix an unresponsive Serial driver adapter. You may have noticed a yellow exclamation mark hovering over or beside the USB to Serial Driver when searching your Device Manager and if you have we can all agree that it signifies a prevailing problem.

Two: No Ports shown in Device Manager (even hidden) Win 7 Pro 64 bit. I can't get an external modem to work (even though it shows in devices and printers window. I can't get a USB-serial port converter to work either. It would be helpful if I had info from the device manager window but nothing show up, even though I have turned on the show.

• Solution 1: Update Prolific USB-to-Serial Driver in Device Manager. The normal way and fast way to solve it is to update the USB to the serial device driver in device manager. It will help Windows 10 recognize the devices again and restart it. Open device manager by right-click Windows icon and choose it from the results.
• Virtual COM port (VCP) drivers cause the USB device to appear as an additional COM port available to the PC. Application software can access the USB device in the This page contains the VCP drivers currently available for FTDI devices. For D2XX Direct drivers, please click here.
• Device Manager Serial Com Port Properties Is there a method using CMD to get the serial port property information that is displayed in the device manager? I would like to take a known COMx port and map that to the physical connection (hub and port) so I can identify which usb device is enumerated by which COM.
• To install serial ports and COM ports using these system-supplied components, do the following: Provide an INF file that specifies the Ports device setup class and the Serial function driver as the service for the port. To configure a serial port as COM port, comply with the requirements that are defined in Configuration of COM Ports.

Overview of the Error

If you are not able to connect your device to your PC using a USB to Serial adapter it may be that

• The USB driver is outdated
• The USB Driver is missing
• Or even a corrupted driver

While you can't be so sure what the exact problem is there are solutions you can adopt to fix the issue once and for all. Read on to find quick fixes to resolve the problem.

1# Fix Prolific USB to Serial Driver not Working

Solution: Roll your Prolific USB to Serial Driver back to an older version

Updating your drivers often work wonders for your system because it makes sure that it runs on the latest features that guarantee maximum functionality. Unfortunately updating your drivers can cause this kind of error especially if your latest update does not work too well with your hardware. Once you upgrade your PC to the latest Windows version your Prolific USB to Serial Driver also updates to the latest driver software and if the driver is not compatible with your Hardware issues may arise. To correct the error, you will have to download the driver again by following these steps.

• Right-click on your PC Start button and open Device Manager

• Double click LPT and COM ports then locate the Prolific USB to Serial Driver and right-click it so you can select Update Driver

• For driver software click My computer

• From My computer select 'Let me pick from a list of drivers available'

• Choose an older version from the list then click Next

• The driver you selected will be installed automatically
• Once it has been downloaded reconnect the driver to see if it works.

2# Fix Prolific USB to Serial Driver 'Coder 10'

Driver issues reveal themselves in so many ways or through messages such as

• This device will not start (Code 10)
• There is no driver installed in this device
• The driver was not successfully installed

A code 10 error may arise because the chip you are using is not an original one. If you are using a fake, the manufacturer has a way of disabling it due to copy write infringement and the copy write takes effect once you download a recent update. To protect your PC from getting this code, you will have to make sure that your Windows 10 never updates a driver without approval. Updates come in the form of 64 bit and 32-bit drivers. Below we will show you how to work your way around the problem.

Window 64 bit Fix

To fix Windows 64 bit OS including Prolific USB to Serial Adapter, follow through these steps.

• Download 'PL2303_64bit_Installer.exe and Save
• Remove every USB to Serial adapter from your PC and double click the 'PL2303_64bit_installer.exe
• Follow the prompt by plugging in one USB to Serial adapter the click on Continue
• Reboot your PC to get Windows up and running

If you have followed these process through and you still see the same error go to your device manager

• Open the control panel and navigate to Device Manager
• From your control panel navigate to the System category and click the Hardware tab
• Scroll to the LPT/COM port and double click Prolific USB to Serial Comm Port
• Click Drivers in the Properties section
• The Driver you choose should read '3.3.2.102 with an appropriate date attached
• If the date is wrong then it means the wrong driver was installed
• Unplug the Serial adapter and run the steps again to install the correct driver

Window 32-bit

For Windows 32-bit OS systems follow these steps

• You will have to download the 'PL-2303_Driver_Installer.exe and save from Microsoft download link
• Run the program and eradicate the driver if you can
• Run the installer once more to install a correct driver

To Troubleshoot for error if your device still does not work

• Go to Control panel, enter System to access your Device Manager
• Scroll down to the LPT/ COM port then double click Prolific USB to Serial Comm Port
• Click Driver in the Windows Properties section
• The driver must be numbered as '2.0.2.8' and dates accordingly

If the driver was not installed, remove the Serial adapter then run 'PL2303_Driver_Installer.exe' again. Follow directions in Device Manager to download the correct driver

The three solutions listed in this article have proven to be quite helpful in fixing a Prolific USB to Serial driver not working on Windows 10. They may appear confusing at first but if you follow each step in detail you can resolve the issue.

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Serial Com Device Port Devices Driver

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This topic describes the registry settings that Serial uses with legacy COM ports. Serial always configures a legacy serial device as a COM port.

Serial queries these entry values when it enumerates a legacy COM port. If a device-specific entry value is not present, Serial uses a Serial service value.

The registry settings for a legacy COM port are under a corresponding legacy COM port subkey that is under the ..ServicesSerialParameters key.

The following entry values are the same as described for a Plug and Play serial device:

• ClockRate

• PortIndex

• Indexed

• RxFIFO

• TxFIFO

• MaskInverted

• DisablePort

• ForceFifoEnable

The following additional entry values are used with legacy COM ports:

PortAddress (REG_DWORD)
Specifies the untranslated base I/O address for the COM port control registers. Serial reads this value. The value cannot be zero. The default value of PortAddress is 0x00000000.

Serial Com Device Port Devices Driver Updater

Interrupt (REG_DWORD)
Specifies the untranslated interrupt vector, as appropriate for the bus type. Serial reads this value. The value cannot be zero. The default value of Interrupt is 0x00000000.

DosDevices (REG_SZ)
Specifies the name of the COM port. The name of a COM port is typically COM<n>, where <n> is a COM port number that the installer obtains from the COM port database. However, a COM port name can be set to any non-NULL string. Serial uses the port name to create a symbolic link to the COM port that is visible in usermode. The default value of DosDevices is a NULL string.

InterruptStatus (REG_DWORD)
Specifies the raw I/O address for the interrupt status register. Serial reads this value. The value is omitted if the port is a stand-alone port. The value cannot be zero if the port is on a multiport device. The default value of InterruptStatus is 0x00000000.

BusNumber (REG_DWORD)
Specifies the system-wide bus number for the bus type. Serial reads this value. The default value of BusNumber is 0x00000000.

BusType (REG_DWORD)
Specifies the bus type. Serial reads this value. The default value of BusType is determined by Serial during driver initialization.

InterruptMode (REG_DWORD)
Specifies the interrupt mode. Serial reads this value. The default value of InterruptMode is CM_RESOURCE_INTERRUPT_LATCHED.

InterruptLevel (REG_DWORD)
Specifies a raw interrupt level value that is appropriate for the bus type. Serial reads this value. The default value of InterruptLevel is 0x00000000.

PnPDeviceID (REG_SZ)
Specifies a Plug and Play device identifier for a Plug and Play device. Serial reads this value. The default value of PnPDeviceID is a NULL string.

Serial Com Device Port Devices Driver Device

LegacyDiscovered (REG_DWORD)
Boolean flag that indicates whether Serial has previously reported the device to the Plug and Play manager. Serial reads and sets this value. If LegacyDiscovered is nonzero, Serial has previously reported the device and does not report the device again. Otherwise, Serial reports the device and sets the entry value to 0x00000001.