1.3 Design Structure

The goal of this course is the design of a camera control system. Its main focus is to demonstrate the application of the hardware description language VHDL in a real world setting. Of course, the problem has been heavily simplified, yet it is powerful enough to point out all main concepts of the language to the beginner. After completing the course you should feel comfortable writing VHDL code on your own.

The camera control system has to generate the appropriate signals for the lens shutter and the film transportation motor. It also generates the input signals for a small 7-segment display showing either the current exposure time or the total number of pictures taken so far. The user controls the camera operation via several keys.

 

Modules of the camera system

 

The central control system that is to be developed during this course is split into seven modules:

  1. A decoder ( decoder ) is used to preprocess the signals from the input device for the controller.
  2. The exposure latch ( exp_ff ) stores the selected exposure time.
  3. A timer for the film transport ( motor_timer ) is used to detect errors during film transportation, e.g. if the film is torn apart.
  4. The exposure controller ( exp_ctrl ) opens the lens shutter for the selected exposure time and counts the number pictures that have been taken.
  5. The photo controller ( main_ctrl ) is the central control unit for the camera control system.
  6. A specialized display controller ( disp_ctrl ) selects the appropriate data for the 7-segment display.
  7. The display driver ( disp_drv ), finally, converts the internal data signals into a format suitable for the output device.
 

The clock frequency of the camera control is 8192 Hz. It allows for exposure times according to the following formula: 2^(-i) seconds (for i = 0..9). You need this information later on in order to implement the required times. The camera control system has to: