【正文】 sed to load/store variables over external memory bus ? _at_ specifies memory address to store these variables ? Byte sent to U_TX_REG by processor will invoke UART ? U_STAT_REG used by UART to indicate its ready for next byte – UART may be much slower than processor – Similar modification for CCDPP code ? All other modules untouched static unsigned char xdata U_TX_REG _at_ 65535。 CntrlInitialize()。 /* initialize the modules */ UartInitialize(uartOutputFileName)。 l++) { buffer[i * 8 + k][j * 8 + l] = CodecPopPixel()。/* part 1 FDCT */ for(k=0。 k++) for(l=0。 i++) for(j=0。 jSZ_COL。 void CntrlInitialize(void) {} void CntrlCaptureImage(void) { CcdppCapture()。 j++) { temp = buffer[i][j]。 } 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。 return (short)(r * .25 * C(u) * C(v))。 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)。 static int FDCT(int u, int v, short img[8][8]) { double s[8], r = 0。 idx++。 idx++。 y++) obuffer[x][y] = FDCT(x, y, ibuffer)。 for(x=0。 } void UartSend(char d) { fprintf(outputFileHandle, %i\n, (int)d)。 rowIndex = 1。 } char CcdppPopPixel(void) { char pixel。 colIndexSZ_COL。 colIndexSZ_COL。 CcdCapture()。 static unsigned rowIndex, colIndex。 colIndex++) { if( fscanf(imageFileHandle, %i, pixel) == 1 ) { buffer[rowIndex][colIndex] = (char)pixel。 for(rowIndex=0。 rowIndex = 1。 } include define SZ_ROW 64 define SZ_COL (64 + 2) static FILE *imageFileHandle。 if( ++colIndex == SZ_COL ) { colIndex = 0。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 ro