RTOS a Case Study of Digital Camara.pptx

RTOS case study

1. 1 case study of digital camera hardware and software architecture, Case Study of Embedded System for an Adaptive Cruise Control (ACC) System in Car, Case Study of Embedded System for a Smart Card, Case Study of Embedded System of Mobile Phone Software for Key Inputs. UNIT-III Program Modeling – Case Studies

2. The digital Camera is used to capture images. It stores the images in the digital format and it does not contain any film. The storage capacity in terms of multiple images in the camera (in a digital format) depends on the amount of memory and the bits used per image. We can download the image into our PC also. The recent possible method for storing the data in the digital camera is using high capacity flash memory or System-on-a-chip i.e. multiple memory and processors on a single IC. The interesting features in the modern digital camera are facilities to store variable size images, deletion of the image, digital stretching, zooming in and out etc. The digital camera embedded system consists of a general-purpose processor, a custom and standard single purpose processor, a memory, and interfaces. A Simple Digital Camera

3. Purpose Digital recording and display of pictures. Processing to get the pictures of required brightness, contrast, and color . Permanent saving of a picture in a file in a standard format at a flash-memory stick (or card). Transfer files to a computer through a port. Inputs Intensity and color values for each picture in horizontal and vertical rows of pixels in a picture frame. Intensity and color values for unexposed (dark) areas in each horizontal row of pixels for offset correction in the row. User control inputs. Signals , events, and notifications User commands given as signals from switches/buttons .

4. Outputs Encoded file for a picture. Permanent store of the picture at a file on a flash-memory stick. Screen display of picture from the file after decoding. File output to an interfaced computer. Functions of the system A color LCD dot matrix displays the picture before shooting. This enables manual adjustment of the view of the picture. For shooting, a shutter button is pressed. Then a charge-coupled device (CCD) array placed at the focus, generates a byte stream in the output after operations by ADC on analog output of each CCD cell. A file is created after encoding (compression) and pixel co-processing as follows: The byte stream is pre-processed E ncoded in a standard format using a CODEC. The encoded picture file can be saved for permanent record. A memory stick saves the file. The file is used for display of recorded picture using a display processor and can be copied or transferred to a memory stick and to a computer connected through a USB port. The LCD displays a picture file after it is decoded (decompressed) using the CODEC. Texts such as picture-title, shooting date and time, and serial number are also displayed. A USB port is used for transferring and storing pictures on a computer. Alternatively, Bluetooth or IR port can be used for interfacing the computer .

5. Power Dissipation: Battery operation. Battery recharging after 400 pictures (assumed) 2. Resolution: High-resolution pictures with options of 2592 x 1944 pixels = 5038848 pixels (3.5M) 2592 x 1728=3.2 M 2048 x 1536 = 3 M 1280 x 960 = IM. 3. Performance: Shooting a 4M pixel still picture in 0.5s. 25 pictures per m (assumed) 4. Process Deadlines: Exposing camera process in a maximum of 0.1s. Flash synchronous with shutter opening and closing. Picture display latency, maximum of 0.5s. 5. User Interfaces: Graphic at LCD or touchscreen display on LCD commands by the camera user through fingers on touchscreen, switches and buttons. 6. Engineering Cost: US$ 50000 (assumed). 7. Manufacturing Cost: US$ 50 (assumed). Design Metrics

6. 1. All user commands must function correctly. 2. All graphic displays and menus should appear as per the program. 3. Each task should be tested with test inputs. 4. Tested for 30 pictures per m. Test and validation conditions

7. MCU Clock Unit Digital Media Processor Flash Memory SD RAM SD/CF/MMC expansion slot Analog Front end USB/IEEE 1394 interface Touch screen LCD control TFT LCD Display User Interface Buttons Shutter & Focus control CCD/CMOS Image Sensor LENS Battery Monitor & charge control DS2770 Voltage Regulator LM7805 S/W controlled Battery ON/OFF Power Supply unit R e c h a r g e a b l e B a t t e r y Components of digital camera Digital Camera Block Diagram

8. Components of Digital Camera 1. Power Supply Unit Rechargeable Battery Battery Monitor & Charge Control (DS2770) Voltage Regulator (LM7805) – Provides stable supply voltage. S/W (soft ware) controlled Battery ON/OFF 2. Core Processing Digital Media Processor – The heart of the system. Handles image processing, compression, and file formatting. MCU (Microcontroller Unit) – Coordinates peripheral control, user interface, and system-level tasks. Clock Unit – Provides timing signals for synchronization. 3. Memory Units Flash Memory – Permanent storage for images. SD RAM( Synchronous Dynamic RAM) – Temporary storage during image capture and processing. SD/CF/MMC Expansion Slot – Allows memory card insertion for extended storage . (SD : Secure Digital, CF: Compact Flash, MMC: Multi Media Card)

9. 4. Image Capture Section Lens – Focuses light onto the sensor. CCD/CMOS Image Sensor ( Charge-Coupled Device) – Converts light into electrical signals (pixel data). Analog Front End – Amplifies and conditions the analog signals from the sensor. Shutter & Focus Control – Provides exposure and focusing mechanisms.   5. Display and Interface TFT ( Thin-Film Transistor) LCD Display – Displays captured images and menus. Touch Screen LCD Control – Allows touch-based user interaction. User Interface Buttons – Additional physical control inputs.   6. Communication & Connectivity USB / IEEE 1394 (FireWire) Interface – Transfers images to a computer or external device.

10. Working description of a Digital Camera Digital Camera-Working A digital camera captures and stores images in the form of digital data, replacing conventional paper/film-based image storage. It contains lens and image sensors for capturing the image, and an LCD for displaying the captured image. Interface buttons are used to control operations, and communication interfaces (USB, etc.) allow transfer of images to a computer. Like normal film cameras, digital cameras use a lens to focus the scene to be captured. Unlike film cameras (where the image is exposed onto film and later developed), in digital cameras, the image is captured electronically . Image Capture Mechanism Charge-Coupled Device (CCD) or CMOS image sensors are used. When exposed to light, these sensors produce electrons, generating analog voltage signals. These signals are processed (filtered, amplified, digitized) by an Analog Front-End (AFE) system. AFE ICs are available from manufacturers like Texas Instruments . Digital Media Processing The digitized data is fed to the Digital Media Processor. The processor implements compression algorithms (JPEG, TIFF, etc.) to reduce file size. Some processors may also include DMA (Direct Memory Access) to transfer compressed images directly to storage memory .

11. System Control Unit Various system functions like shutter control and zooming control are performed by the System Control Unit . The System Control Unit is implemented using a 16/32-bit microprocessor or microcontroller . Power Management The camera is powered by a rechargeable battery . Battery monitoring and charging control is carried out by a Battery Charge Control & Monitor IC . This IC operates under the supervision of the System Control Unit . Storage & Connectivity Provisions for interfacing storage memory devices like: SD (Secure Digital) CF (CompactFlash) MMC ( MultiMedia Card) The camera can be connected to a PC through communication interfaces such as: USB (Universal Serial Bus) IEEE 1394 (FireWire) These interfaces support image transfer to external devices.

12. System-on-Chip ( SoC ) Modern digital cameras use a single-chip SoC that incorporates both: The Image Processor A 16/32-bit Microprocessor This integration improves performance and reduces size/power consumption. Resolution Resolution of a digital camera is expressed in megapixels (MP) . It represents the pixels per inch of the image sensing device. As the number of pixels increases , the image quality improves . Embedded Operating System Various system control tasks and image capturing/processing tasks are implemented using an Embedded Operating System (RTOS/Embedded OS) . The embedded OS ensures: Efficient task scheduling Real-time response to user inputs Coordination between hardware (sensors, memory, display) and software (image processing algorithms).

13. Three Stage Diagram of Digital Camera System

14. System layer: System layer provides system services, for example, display text with the picture, flash start and stop after timeout of an auto timer, saving and retrieving of processor internal registers, and OS vices such as IPCs (inter-process communication). Application layer: Application layer is for system switches, button and control tasks. Examples are flash. light, contrast and image view before shooting. Function layer: Function layer is for application layer tasks functionality using Picture File Creation . Picture File Display and Picture File Transfer . Presentation layer: Presentation layer is for providing standard access to an image file. Examples are the default settings of image contrast, resolution, outputs, display color setting, sound of clicks. time and date display, dot-matrix or touchscreen driver, ADC output format and data outputs. Control layer: Control layer is for Controller Tasks , timer control and real time control modules. Base layer: Base layer provides a standard access to the internal devices in the microcontroller. Internal device examples are timer, real-time clock, SI (serial interface), ADC, and USB port DIGITAL CAMERA SOFTWARE ARCHITECTURE

15. Designer’s perspective From the designer’s perspective a simple digital camera is capable of performing two key tasks. The first task involves capturing the images and when the shutter is pressed the captured image is converted to a digital form using a charge-coupled device (CCD)). Then the digital format images are compressed and archived in the internal memory. The second task involves uploading the images to the PC. This process is implemented by attaching the digital camera to the PC and giving special software commands to transmit the images serially from camera to PC.