Digital camera as embedded system

A digital camera is a good embedded system because it has one dedicated function (capture, process, compress and store images), uses a processor with memory and I/O, runs fixed firmware, is tightly constrained (small, cheap, low power, fast), is real-time (the image must be processed quickly) and reacts to the environment through a sensor and user buttons.

Block diagram

 Lens -> [CCD/CMOS] -> [A/D] -> +-------------------+
 light    sensor                |  Microcontroller   |
                                |  (CPU, firmware)   |
 Buttons ---------------------> |                    |
 LCD <-------------------------<|  JPEG codec (DSP)  |
                                |  Memory controller |
                                +--------+-----------+
                                         |
                          [DRAM]   [Flash/memory card]  [USB/UART]

Explanation

• Lens and CCD/CMOS sensor: converts light into charge on a pixel array (rows and columns).
• A/D converter: converts the analog pixel charge into digital values.
• Microcontroller (CPU): runs firmware that controls the shutter, flash, auto-focus, and user interface.
• JPEG codec / DSP: compresses the image (DCT, quantisation, Huffman coding) to save storage.
• Memory: DRAM holds the image during processing; flash/memory card stores pictures permanently; ROM holds firmware.
• Display (LCD) and buttons: the user interface.
• USB/serial port: transfers pictures to a PC.

It also shows the design-metric trade-off: the designer must keep power, size and cost low while keeping speed (a few images per second) high.