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VNC terminal

VNC terminal
Picture 1. VNC terminal

One of our developments was hardware-software system to work with the secrete documentation. It consists of the server part, which keeps documents and provides authentication; control access of isolation and data security; and the hardware thin client consigned to organise the work place of PC operator. Complex architecture permits the independent transmission of external documents into the system, including downloads from the Internet. In general, there were three versions of the system developed, which differ by the model of processor in the client, by methods of authentication on the server and by data security.

In a second version of the client, the Atmel AT91RM9200 processor is used, and it is working on a frequency of 100 MHz. Connection with the server is produced by twisted pair or by optical cable. For authentication, the contact smart-card is used. The monitor is connected through standard 15-pin VGA jack. The keyboard and the mouse are connected to the same port PS/2 (through special conductor).

The second modification of our thin client, works without an operating system. For connection with the server the VNC protocol is used. The client's task is the processing of incoming VNC flow from the server, data display, processing of events from the keyboard, the mouse, the smart-card, and data shipping on the server. In this way, we programmatically realised:

  • VNC protocol
  • Mouse driver and keyboard driver
  • Driver and work with the contact smart-card;
  • Driver of video processor;
  • Adaptation of network protocol stack TCP/IP – LwIn
  • Creation of link layer of stack TCP/IP
  • Communication of debugging data through COM port

The video chip manages the display output composed in Altera Cyclone.Its tasks are to get data from the CPU via bus from the server to the display; to form page in the video memory; to form the video signal by this page; and display the formed page with the speed of 60 GHz. Video modes 800x600 and 1024x768 are supported. The micro chip Realtek rtl8201 manages access to the physical layer of the protocol stack. The main part of programming realisation of the client is in external chips of flash memory.

The constructively finished product is covered in a plastic case with the metal bottom and complete passive cooling. The external power supply has to provide 5V voltage with 3A direct current.

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