N2PK VNA Parallel/USB Interface

by Evgeny, VE3SSR

Parallel to USB interface could be easily implemented using cheap CY7C68013A Mini boards available on ebay for $10. (Please make sure that I am not affiliated anyhow with suppliers or distributors of the board, just want to mitigate a suffer of your family budget  caused by your adherence to Ham Radio).

The board consists of USB chip with integrated controller and EEPROM memory AT24C128 (8-legged chip on a picture). The EEPROM should contain device ID called PID/VID (Product and Vendor ID). These IDs are needed to recognize the device and to assign a correct driver.

To program PID/VID into EEPROM no special hardware programmer required.  USB Interface Configuration Utility developed by Dave, G8KBB will do the job. Initially I tried to keep original EEPROM installed on the board, however it was not recognized by the Utility because of wrong size and/or wrong PID/VID pre-programmed in it, so I decided to unsolder  it (I have re-work station, though, you may do it with big soldering iron or using other techniques) and to install 24LC64 which is implemented on latest VNA boards. The 24LC64 costs around 55 cents on Digikey (24LC64-I/SN-ND). Since the empty EEPROM was recognized by the Utility, I managed to program the IDs. Though, I beleive there is a way to use original EEPROM installed on the board. If you find it, please let me know.

When running the Utility, click on “Setup” tab and then on “Find Devices” button to check, whether the interface is recognized or not. If the window is empty – your device has not been recognized. That means the EEPROM is not empty or PID/VID are not relevant to N2PK devices.

Dave gave step-by step instructions how to use his USB configuration utility to program the EEPROM for operation as an N2PK VNA USB interface. See N2PK VNA USB Interface hardware guide , page 8. There are also instructions how to load the drivers.

On the pictures below you can see my test rig which consists of the USB board and N2PK VNA with parallel interface. I would like to thank Nick, VE3FJ, who built the VNA and allowed me to use it for testing the USB Interface.

As a temporary solution I used color wires with female connectors to bound the board to VNA. It took me about 10 minutes to wire and test the interface which worked quite well, e.g. exactly the same way as those on V5 boards.

After 20 minutes of operation the temperature of the USB chip was close to ambient, so apparently, it does not consume much power.

 Mini Board  VNA USB INTERFACE board (Large)
  VNA USB INTERFACE overview (Large)  VNA USB INTERFACE board 2 (Large)

Below is a connection table.




7 PB0 DET1 2 SCK
8 PB5 DET1 nCS
9 PB1 DET2 nCS
11 PA7 DET1 nSDO
12 PB7 DET2 nSDO
  PB6 VNA PWR via 10K resistor

73, Evgeny, VE3SSR

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3 Responses to N2PK VNA Parallel/USB Interface

  1. Kari B says:

    Hi, this looks a very easy approach move to usb with VNA…
    The card came today, then quick check with the drivers…

    Unfortunately old xp with sp3 rejected installing drivers also the newer xp-specific drivers… so CY card is not identified by the windows at all.
    Could there be conflict with the CY-card internal eeprom as it’s probably factory preprogrammed for something and has non-VNA content ?
    I am waiting 24LC64 chips to change it, but they are still on a way…
    Haven’t yet check the Cypress tools if available and drivers if they are able to connect the card and clear the eeprom…

    Curiously I must enquiry what windows version you did use ? Did the windows drivers
    installed ok for the CY-card but the VNA specific download failed before removing the 24LC128 ?

    Do you have other routes to identify the driver conflict please ? I have expected some experimenting as most things usually need it…

    Kind regards
    Kari B

    ps. parallel port vna functions well, but USB might minimize slightly the
    data transfer used…

  2. Evgeny says:

    Hello Kari,
    I had some issues with 24LC128, you right, it was preprogrammed with kind of firmware and was not recognized by USB Interface Configuration Utility.
    Everything went smoothly when I installed 24LC64. It was instantly recognized .
    Just follow Dave’s instructions.
    I did it with Windows 7, but quite sure you should have no problem with XP.
    73, Evgeny, VE3SSR

  3. Kari B says:

    Hi, a delayed response…
    VNA sw downloads without troubles, this USB card is really neat to add the USB feature to substitute original parallel port.
    It looks changing the eeprom is a must, I didn’t found quickly way use the original while waiting the new ones by mail…

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