未安装驱动程序时如何禁止FTDI .NET DLL提醒用户

Question

I have a C# application that's using the FTD2XX.DLL from FTDI. This application is used for multiple generations of a single product and abstracts the physical hardware. There's an FTDI and a HID implementation.

The application searches for both appropriate FTDI and HID devices, though it's likely that no FTDI drivers exist if the user has the HID generation.

Background aside now. When I instantiate the FTDI class I get a modal, not generated by my code about not finding the FTDI driver and asks the user if the drivers are installed. I tried wrapping this in a TRY/CATCH block but no exception is thrown.

1: Is there a way to determine if the FTDI drivers are installed before trying to instantiate the FTDI class?

2: If not, is there a way to prohibit the FTDI dll from alerting the user when this happens?

Answer 1

I have the exact same requirements - in my case I'm enumerating the list of standard serial ports and appending this with the list of any attached FTDI devices. If the driver isn't installed, then I'd like to not have those modal dialog boxes appear. One quick and dirty way I've figured out to do this is to check for the file FTD2XX.DLL being in c:\\windows\\system32 (or wherever windows is installed). The existence of this file basically means the driver is installed.

// c# example
string path = Environment.GetFolderPath(Environment.SpecialFolder.System);
bool installed = File.Exists(path + Path.DirectorySeparatorChar + "FTD2XX.DLL");

Answer 2

Another way:

[DllImport("kernel32.dll")]
private static extern IntPtr LoadLibrary(string dllToLoad);
[DllImport("kernel32.dll")]
private static extern bool FreeLibrary(IntPtr hModule);    

public bool IsDriverInstalled()
{
  //trying to load library
  IntPtr handler = LoadLibrary(@"FTD2XX.DLL");

  if (handler == IntPtr.Zero)
      return false;
  else
      return true; // Driver is installed

  //Don't forget to free .dll
  FreeLibrary(handler);
}

Answer 3

It sounds as though you are bundling FTD2XX.DLL with your application.

You shouldn't do this, you should use the latest DLL installed into the Windows system directory by the FTDI driver. If you have an old version of the DLL in your app directory, and the user has newer drivers (possibly installed by some other FTDI-based device), you could have all kinds of trouble.

As a bonus, this solves your problem in most cases: If FTD2XX.DLL isn't installed on the system, you'll get an exception trying to p/invoke, which you can catch.

To avoid the error perfectly, however, you'll need to do the same check that the FTD2XX.DLL does internally (since the DLL obviously can exist on the system without any driver). For example, checking whether the driver is listed in the registry under HKLM\\System\\CurrentControlSet\\services would be a more robust check than the one you have. Still not sure if it's equivalent to FTDI's own check.

Answer 4

I rewrote the FTDI library that was causing the error: it was caused by a MessageBox.Show in the constructor. I have replaced this with a normal Exception throw.

See my blog for the re-engineered wrapper and code: connecting to FTDI devices in Silverlight 5 RC