Paul Kiciak, N2PK, has produced a very elegant Vector Network Analyser. You can read all about it on his website. It is controlled via the parallel port from a PC. As an alternative to parallel, USB offers many advantages. Here you will find details on how to build a USB interface to work with the VNA. Note however that this interface requires suitable software to control it - you cannot simply "use" this with the DOS programs. The interface works with VNA4win and with Exeter
In addition, the structures and methods used are generally applicable to other projects - feel free to make use of this for Amateur Radio purposes. You could consider this a worked example of how to build a USB peripheral using the Cypress FX2.
The USB Interface is designed to be compatible with the Elrasoft module, but may be easily constructed. In addition the code runs on KB6DHW’s HSUSB board and also in Ivan’s new V5 VNA.
There are two parts to download for the software - the documentation and the code. There is one part to download for the hardware. If you want the VNA/USB pinout information it is now in the hardware guide.
There is also a configuration utility for programming the EEPROM on the USB interface board for operation with the VNA. All executables and code are to be found here.
The latest version (0.22) has three changes. First, it is much faster, and second it is required for myVNA v0.31 or later as it implements the switching functions for single detector RF IV scans. Finally, two versions are supported - the normal configuration and a 500mA option for situations where the USB interface is used to power the VNA. This is selected by programming the appropriate PID into the EEPROM. A new version of USB Configure is available to do this. In addition, both the low and high current options are available for Ivan’s V5 board.
The drivers have also now been updated to use cyUSB with 32 and 64 bit drivers for XP, Vista and Windows 7. A new version of USB Configure is also included. If you use these drivers you MUST also replace vnadll.dll with the new version that is also included in the driver package. Credit and thanks to Ivan for procuring a live code signing key for the drivers.
Note: If you use the new V5 board you MUST program it with the identity of a V5 module. This is because the driver is subtly different to the V4 and previous interfaces because the transistor inverter between the ADCs and the USB chip is no longer there so the ADC data line is inverted. When using the USB Configure utility, new options for V5 are now also presented for this purpose.
Timing data and screenshots may be found here