【正文】 {} void CntrlCaptureImage(void) { CcdppCapture()。 } 24 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis CNTRL (controller) module ? Heart of the system ? CntrlInitialize for consistency with other modules only ? CntrlCaptureImage uses CCDPP module to input image and place in buffer ? CntrlCompressImage breaks the 64 x 64 buffer into 8 x 8 blocks and performs FDCT on each block using the CODEC module – Also performs quantization on each block ? CntrlSendImage transmits encoded image serially using UART module void CntrlSendImage(void) { for(i=0。 x++) { s[x] = img[x][0] * COS(0, v) + img[x][1] * COS(1, v) + img[x][2] * COS(2, v) + img[x][3] * COS(3, v) + img[x][4] * COS(4, v) + img[x][5] * COS(5, v) + img[x][6] * COS(6, v) + img[x][7] * COS(7, v)。 idx++。 y++) obuffer[x][y] = FDCT(x, y, ibuffer)。 } void UartSend(char d) { fprintf(outputFileHandle, %i\n, (int)d)。 } char CcdppPopPixel(void) { char pixel。 colIndexSZ_COL。 static unsigned rowIndex, colIndex。 for(rowIndex=0。 } include define SZ_ROW 64 define SZ_COL (64 + 2) static FILE *imageFileHandle。Embedded Systems Design: A Unified Hardware/Software Introduction Chapter 7 Digital Camera Example 1 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Outline ? Introduction to a simple digital camera ? Designer’s perspective ? Requirements specification ? Design – Four implementations 2 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis ? Putting it all together – Generalpurpose processor – Singlepurpose processor ? Custom ? Standard – Memory – Interfacing ? Knowledge applied to designing a simple digital camera – Generalpurpose vs. singlepurpose processors – Partitioning of functionality among different processor types Introduction 3 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Introduction to a simple digital camera ? Captures images ? Stores images in digital format – No film – Multiple images stored in camera ? Number depends on amount of memory and bits used per image ? Downloads images to PC ? Only recently possible – Systemsonachip ? Multiple processors and memories on one IC – Highcapacity flash memory ? Very simple description used for example – Many more features with real digital camera ? Variable size images, image deletion, digital stretching, zooming in and out, etc. 4 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Designer’s perspective ? Two key tasks – Processing images and storing in memory ? When shutter pressed: – Image captured – Converted to digital form by chargecoupled device (CCD) – Compressed and archived in internal memory – Uploading images to PC ? Digital camera attached to PC ? Special software mands camera to transmit archived images serially 5 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Chargecoupled device (CCD) ? Special sensor that captures an image ? Lightsensitive silicon solidstate device posed of many cells When exposed to light, each cell bees electrically charged. This charge can then be converted to a 8bit value where 0 represents no exposure while 255 represents very intense exposure of that cell to light. Some of the columns are covered with a black strip of paint. The lightintensity of these pixels is used for zerobias adjustments of all the cells. The electromechanical shutter is activated to expose the cells to light for a brief moment. The electronic circuitry, when manded, discharges the cells, activates the electromechanical shutter, and then reads the 8bit charge value of each cell. These values can be clocked out of the CCD by external logic through a standard parallel bus interface. Lens area Pixel columns Covered columns Electronic circuitry Electromechanical shutter Pixel rows 6 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Zerobias error ? Manufacturing errors cause cells to measure slightly above or below actual light intensity ? Error typically same across columns, but different across rows ? Some of left most columns blocked by black paint to detect zerobias error – Reading of other than 0 in blocked cells is zerobias error – Each row is corrected by subtracting the average error found in blocked cells for that row 123 157 142 127 131 102 99 235134 135 157 112 109 106 108 136135 144 159 108 112 118 109 126176 183 161 111 186 130 132 133137 149 154 126 185 146 131 132121 130 127 146 205 150 130 126117 151 160 181 250 161 134 125168 170 171 178 183 179 112 124136 170 155 140 144 115 112 248 12 14145 146 168 123 120 117 119 147 12 10144 153 168 117 121 127 118 135 9 9176 183 161 111 186 130 132 133 0 0144 156 161 133 192 153 138 139 7 7122 131 128 147 206 151 131 127 2 0121 155 164 185 254 165 138 129 4 4173 175 176 183 188 184 117 129 5 5Covered cells Before zerobias adjustment After zerobias adjustment 1311907145Zerobias adjustment 7 Embedded Systems Design: A Unified Hardware/Software Introduction, (c) 2023 Vahid/Givargis Compression ? Store more images ? Transmit image to PC in less time ? JPEG (Joint Photographic Experts Group) – Popular standard format for representing digital images in a pressed form – Provides for a number of different modes of operation – Mode used in this chapter provides high pression ratios using DCT (discrete cosine transform) – Image data divided int