I had previously failed to connect my Novag Citrine to Arena, and thought that my USB-to-Serial adapter was at fault. I recently decided to gather all the information that I could and have another try.
The Novag Cirine instruction manual can be found here:
Here are instructions for interacting with the Citrine via Hyperterminal:
Unfortunately, Hyperterminal was discontinued by Microsoft from Vista onwards. Even when the Citrine's internal engine is being used, interaction with a PC can be be very useful. The Citrine lacks the additional buttons that some dedicated chess computers have, and its user interaction is not the best. It is easy to get a situation where the position on the board differs from that in the Citrine's processor, and it can be difficult to sort the problem out. It is also useful to be able to get a score of the game.
I found that a precise procedure had to be followed to connect the Novag Citrine to Arena 3.5.
Make sure that the Citrine is turned off.
Connect the “LCD box” to the Citrine via the “LCD box connection cable”. Connect the USB-to-Serial adapter to the “LCD box” via the “PC connection cable”. Plug the USB-to-Serial adapter's USB plug into a USB socket on the PC.
Start Windows 10. Type “Devices” into the search box in the lower left hand corner of the screen. Select the “Devices desktop app”. My PC shows “Prolific USB-to-Serial Comm Port (COM3)”.
Start Arena. Select Extras > “Configure Novag-Chessboard”.
Select the Options tab. Select the COM3 radio button (or whatever COM port showed in Devices).
Select the Start tab. Click the “Start Novag Support” button.
Switch the Citrine on.
Select the Information tab. Click the “Get Information” button. My PC shows “ID UCB11 V1.09”.
Select the Communications tab. Type P into the text box. Click the “Send to Novag!” button. My PC responds with the start position.
Subsequently, to play against Arena, making moves on the Citrine board, start Windows 10, and start Arena. Click the new game icon. Select Extras > “Novag – Chessboard”. Turn the Citrine on. Make your move on the Citrine board. Arena should echo your move on the Arena board. It should then make its reply on that board, and flash that reply on the Citrine board.