January 3, 2010
1 Overview of mobile phone camera phone camera
1.1 Overview
mobile phone digital camera refers to whether the phone or through the built-in external digital camera to take still pictures or video filming, as additional mobile phone features a new, digital camera mobile phone has been rapid development. Divided into the built-in phone camera and external, built-in camera is the camera inside the phone, and more convenient. External mobile phone via data cable or phone connected to the lower part of the interface with the digital camera, digital camera to complete all the shooting. The advantages of an external digital camera can reduce the weight of mobile phones, digital cameras and external light weight, easy to carry, easy to use. At the development stage of the performance of digital cameras, mobile phones should also be in its infancy, mobile phone with optical zoom, domestic sales have not this feature, but I believe that with the development of mobile digital camera, mobile phone with optical zoom will market gradually, but most have digital zoom function. In addition, the current digital camera phone features include still image capture, shot, video capture, the lens can be rotated, auto white balance, built-in flash and so on. Shooting functions to their mobile phone screen material, screen resolution, camera pixels, the camera is directly related material.
1.2 Camera is generally divided into categories
Camera Digital camera and Digital Still Cameras Digital Analog.
1.2.1 Digital camera Digital
digital camera directly to the camera unit and the integrated video capture unit, and then serial, parallel or USB interface to connect to HOST SYSTEM on. CAMERA is now on the market of basic digital camera camera-based, while the digital camera turned around to use the new data transfer interface, USB digital camera-based (independent), mainly on the phone directly through the IO (BTB, USB , MINI USB …) connected with the HOST SYSTEM, through HOST SYSTEM editing the digital signal output to the DISPLAY on the display. Currently on the market mainstream CAMERA CAMERA full DIGITAL
CAMERA.
1.2.2 Simulant camera analogue camera
analog video capture device is to generate analog video signals into digital signals, and then save it in to the SYSTEM MEMORY. Analog cameras capture the video signal must be specific video capture card analog signal into digital mode and to be compressed before they can switch to HOST SYSTEM on the use of, the HOST SYSTEM editing, display and output through the DISPLAY.
1.3 Camera structure
1.3.1 CCD structure
divided into three layers: LENS, color filter, photosensitive layer
Level 1 LENS: CAMERA key imaging SENSOR, In order to expand the lighting rate of CCD pixels must be expanded by a single area of ??light, while the rate of increase will lead to light picture quality. LENS is equivalent to an increase in front of a pair of glasses SENSOR, SENSOR lighting rate of the open area is not determined by the SENSOR LENS surface area but by the decision.
color filter layer 2:
Currently, there are two color color filter method: RGB primary color separation method, that is, RGB color separation method, almost all of the human eye can recognize The colors can be formed by RGB, RGB is the color by adjusting the three channels together.
CMYK fill color separation method, the color match from the four channels from, respectively, green (C), magenta (M), yellow (Y), black (K), but not as good as RGB color adjustment out of the Many colors.
Layer 3 SENSOR
CCD photosensitive layer of the third layer is the SENSOR, SENSOR mainly through the color filter layer is to convert light into electronic signals, and signal to the image processing chip (DSP), will Image Restoration.
1.3.2 LENS (lens)
general CAMERA lens structure lens is composed of several pieces, divided into plastic lens (PLASTIC) and glass lens (GLASS), usually with the lens structure CAMERA: 1P , 2P, 1G1P, 1G3P, 2G2P, 4G and so on. Lens, the more the higher the cost; glass lens plastic lens than the expensive, but the glass lenses of the imaging lens than the image better than plastic. Currently on the market for MOBILE PHONE CAMERA configured to 1G3P (1 pieces of glass lenses and plastic lenses 3) the main purpose is to reduce costs.
1.3.3 SENSOR (image sensor)
image sensor (SENSOR) is a semiconductor chip, the surface contains several hundred thousand to several million photodiodes. Photodiode by light irradiation, will have a charge. There are two types present SENSOR: CCD (Charge Couple Device), charge-coupled device CMOS (Complementary Metal Oxide Semiconductor), complementary metal oxide semiconductor
1.3.4 A / D converter
A / D converter is ADC (Analog Digital Converter ADC) ADC, two important indicators are quantitative conversion speed and accuracy, as CAMERA SYSTEM in the large volume of high-resolution image pixels, and therefore the requirements of high speed converters. While the corresponding quantization precision ADC converter will the brightness of each pixel and color values ??to quantify the level if the
dry, this level is CAMERA color depth. Already have the CMOS digital transmission interface, so you do not A/D4.0 digital signal processor (DSP) digital signal processing chip DSP (DIGITAL SIGNAL PROCESSING) Function: mainly through a complex series of mathematical algorithms operation of the digital image signal optimized parameters, and to processed signals transmitted via USB, PC and other equipment.
1.3.5 DSP frame of
1. ISP (image signal processor) (image signal processor)
2. JPEG encoder (JPEG image decoder)
3. USB device controller (USB device controller)
1.4 Camera Specifications
1.4.1 Image compression JPEG
(joint photographic expert group) still image compression. A lossy image compression. Higher compression ratio, the worse the image quality also. When the image is limited storage space less precision, you can choose this format. Currently, most digital cameras use JPEG format.
1.4.2 image noise
refers to the image noise interference, expressed as a fixed image color noise. View
1.4.3 and is similar to the human eye imaging principle, it simply is imaging range.
1.4.4 white balance processing technology (AWB)
required color temperature in different environments, according to a white object, the screen image should also white. Spectral components, said color temperature of light colors. That long wavelength components of low color temperature and more. When the color temperature changes, light in three primary colors (red, green, blue), the ratio will change, you need to adjust the ratio of the three primary colors to achieve color balance, white balance adjustment that is practical. Image sensor image data is read, the system will be its edge against the lens distortion correction operations, and then after a bad deal after a system like to send into the white balance processing (in a different light environment, the human eyes can leave some “white” color of the objects are seen as white, because the human eye is modified. but SENSOR no such function, so the need for the output signal SENSOR some amendments, this is the white balance processing technology).
1.4.5 Power internal power supply is a good camera, camera stability to ensure a factor.
1.4.6 color depth (color digits)
reflect the recognition of color and color performance imaging capabilities, that is, the number of bits of binary digits used to record the three primary colors. Is actually the A / D converter quantization precision, refers to the number of the signal is divided into grades, commonly used color-digit (bit) said. The higher color depth, color images obtained by the more colorful and moving. SENSOR is generally non-professional 24-bit; professional SENSOR at least 36. 24-bit SENSOR, light-sensitive unit to record the brightness values ??of up to 2 ^ 8 = 256 levels, each with an 8-bit color binary digits to record up to record the color is 256 × 256 × 256 of about 16,77 million.
36-bit SENSOR, light-sensitive unit to record the brightness values ??of up to 2 ^ 12 = 4096, each primary color with a 12-bit binary numbers to record up to record the color is 4096 × 4096 × 4096 About 6.87 billion kinds.
1.4.7 Input / output port (IO)
serial interface (RS232/422): slow transfer rate, for the 115kbit / s.
parallel port (PP): speed up to 1Mbit / s.
infrared interface (IrDA): rate is 115kbit / s, a typical laptop with this interface.
Universal Serial Bus USB: Plug and Play interface standards, support hot plug. USB1.1 speeds of 12Mbit / s, USB2.0 up to 480bit / s.
IEEE1394 (FireWire) interface (also known as ilink): The transmission rate of up to 100M ~ 400Mbit / s.
1.4.8 image format (image Format / Color space)
RGB24, I420 is the most commonly used two kinds of image formats. RGB24: that R, G, B three colors of the 8bit, up to the performance of color.
I420: YUV formats.
other formats: RGB565, RGB444, YUV4: 2:2 and so on.
1.4.9 Resolution (Resolution)
resolution refers to the so-called resolution of the screen, the number of pixels formed by the larger number, the more clear image. Not only related to the size and display resolution, but also by the CRT dot pitch, the video bandwidth and other factors. We usually see a resolution of the multiplication of forms and manifestations, such as 1024 * 768, where the horizontal direction on the screen 1024 that shows the number of points, 768 indicated that the vertical points.
SXGA (1280 x1024), also known as 1.3 million pixel
XGA (1024 x768), also known as 80 million pixels
SVGA (800 x600), also known as 50 million pixels
VGA (640×480) also known as the 30 million pixels (35 million is 648X488)
CIF (352×288), also known as 10 million pixels
SIF / QVGA (320×240)
QCIF (176×144)
QSIF / QQVGA (160×120)
1.5 Camera Work
scene (SCE) through the lens (LENS) generated optical image projected onto the image sensor (Sensor)
surface, and then converted to electrical signals, after A / D (analog-digital conversion) converted into a digital image signal, and then sent to digital signal processing chip (DSP) in the processing and then transferred to the CPU through the IO interfaces to handle, you can see by the image of the DISPLAY.
1.6 Camera explain commonly used terms
1.6.1-pixel digital camera, including the number of pixels Effective pixels (Effective Pixels) and maximum pixels (Maximum Pixels). The difference is that the maximum effective pixel number of pixels is the real pixel value in photographic imaging, and the highest pixel value is the true light-sensitive device pixels, the data usually contains some sensitive non-imaging device, while the effective pixels in the zoom lens out under the conversion rate values. Pixel digital camera for mobile phones, currently only in the initial stages of development, the number of pixels is not very high, most of the 30 million – 200 million pixels. The greater the number of pixels digital camera, the resolution still images taken greater, the corresponding space occupied by a picture will increase.
1.6.2 Effective pixels Effective pixels
English name for Effective Pixels. And the maximum pixel difference, the effective number of pixels is a real photographic image in pixels. The maximum pixel value is the true light-sensitive device pixels, the data usually contains some sensitive non-imaging device, and effective pixel is converted under magnification zoom lens out of the value. Storage of digital images are generally pixel (Pixel) as a unit, each pixel is the smallest digital unit of the picture. Pixels larger area of ??the larger picture. To increase the size of a picture, if not more light into the light-sensitive devices, the only way is to increase the size of pixels, so that may affect the strength and clarity of the image sharp. Therefore, under the same pixel size, digital camera images to get the most pixels, is the effective pixels.
1.6.3 Maximum pixels maximum pixel
English name for the Maximum Pixels, pixel is the result of the so-called maximum obtained after interpolation. Interpolation in a digital camera through a DSP chip inside, the need to enlarge the image interpolation using nearest neighbor method, linear interpolation computation method, to add the image to enlarge the image after the need to increase the pixels. After the interpolation can not be obtained with the true image quality of images compared to photographic imaging. Pictures taken with the greatest pixel smaller than the effective pixel resolution taken.
1.6.4 Sensor shooting as the new phone features, built-in digital camera function and we usually see low-end (30 million – 200 million pixels) digital camera the same. Compared with traditional cameras, traditional cameras, “film” as the information carrier of its records, and digital camera “film” is its light-sensitive imaging devices, and is integrated with the camera, is the heart of digital cameras. Digital camera light sensor is the heart of the most critical technologies. The core of current mobile phone digital camera imaging components, there are two: one is the widely used CCD (charge-coupled) components; the other is CMOS (complementary metal oxide conductor) devices.
1.6.5 CCD
charge coupled device image sensor CCD (Charge Coupled Device), which uses a high-speed semiconductor material, can light into electric charge, through the ADC chip into a digital signal, digital signal compressed by the camera after the internal flash memory card or internal hard save, so you can easily transfer the data to the computer and computer-based processing tools, and imagination needed to modify the image . CCD by a number of sensitive units, usually in units of megapixels. When the CCD surface by light irradiation, each light-sensitive charge will be reflected in the component unit, all the signals produced by light-sensitive units together to form a complete picture. CCD compared to the traditional film, CCD closer eye on the visual work. But the human eye retina is responsible for the induction of the rod cells of light intensity and color sensing cone cells, division of labor between visual perception of form. CCD after 35 years of development, roughly the shape and mode of operation have been stereotyped. Is mainly composed of CCD, a similar mosaic grid, condenser lens and the pad on the bottom of the matrix composed of electronic circuits. Currently the company has the capacity to produce CCD are: SONY, Philps, Kodak, Matsushita, Fuji, and Sharp, most of the Japanese manufacturers.
1.6.6 CMOS
complementary metal oxide semiconductor CMOS (Complementary Metal-Oxide Semiconductor) and CCD in digital cameras the same as in the semiconductor light changes can be recorded. CMOS manufacturing technology and general computer chips no difference, mainly using both silicon and germanium semiconductors made of elements to make it coexist with the CMOS on N (with a – e) and P (with a e)-class semiconductors, these two complementary effects can be generated by the current record and interpreted chip image. However, CMOS is too prone to the shortcomings of noise, mainly because of early design to CMOS image in dealing with rapidly changing, due to current changes are too frequent and cause overheating.
1.6.7 CCM
CCM is actually a CMOS camera, but CCM higher image quality than CMOS, speed sensor to take pictures quickly, but picture quality is still inferior to CCD camera, in the actual also can feel it shooting, shooting speed is very fast, even if the fast moving mobile phone camera, the screen can catch them quickly display screen, the process is very smooth, almost no delay.
1.6.8 CCD and CMOS
by two different working principle of light-sensitive device can be seen, CCD has the advantage of image quality is good, but due to complex manufacturing process, only a few manufacturers to master, so lead to high manufacturing costs, especially for large CCD, the price is very high. In the same resolution, CMOS cheaper price than CCD, but the image quality produced by CMOS devices is to be lower than CCD. So far, the vast majority of the market and the high-end consumer-level digital cameras use CCD sensors as; CMOS sensors are used in some low-end products as the camera head, and if the camera manufacturers Which camera to the first use of CCD sensors, manufacturers will spare no effort to its hype as a selling point, even as a “digital camera” in the name. For a time, whether the CCD sensor into a digital camera to determine the grade of people in the world. One advantage of CMOS image sensor is lower power consumption than the CCD, CCD to provide excellent image quality, pay a price that is higher power consumption, for the charge transfer smooth, noise reduction, need to improve the transmission effect from the pressure differential . However, each pixel CMOS image sensor to convert the charge voltage, read before they put the zoom, can be driven by 3.3V power supply, power consumption is lower than the CCD.
CMOS image sensor, another advantage of the integrated circuit with the surrounding high signal processor can be integrated with the ADC, so that the volume significantly reduced, for example, CMOS image sensors need a power supply, CCD has power to be three or four groups, the ADC and the signal processor processes and CCD is different from CCD to reduce the size of the package is very difficult. CMOS image sensors but the essential problem is to reduce noise generation, the future can change the CMOS image sensor is CCD depression has long been the fate, future technology development is key. The development of light-sensitive CCD device by the United States in 1969 by Bell Labs developed. Into the 80 , CCD image sensor though flawed, due to continuing research and finally overcome the difficulties, and in the latter half of the 80 to create high-resolution and high-quality CCD. To create 90 megapixels of high resolution CCD, this time the development of CCD is leaps and bounds, calculate CCD development so far has more than twenty years in a row. Into the mid 90 , CCD technology has been rapid development, while, CCD unit area is also getting smaller and smaller. However, in the CCD image area is reduced while improving the image quality, SONY and 1989 developed a SUPER HAD CCD, this new device is a light-sensitive area is reduced in the case of CCD, CCD components rely on amplification of the internal amplifier magnification to enhance image quality. Have occurred after the NEW STRUCTURE CCD, EXVIEW HAD CCD, four-color filter technology (the application for SONY F828). Fuji digital camera is using the Super CCD (Super CCD), Super CCD SR. For CMOS, it has the ease of mass production, high speed, low cost, will be key components in digital camera, the direction of development. At present, the continuous efforts of companies such as CANON, the new CMOS devices continues to introduce new, high dynamic range CMOS devices has emerged, this technology eliminates the shutter, iris, automatic gain control and gamma correction needs, bringing them closer to the CCD image quality. In addition, as CMOS innate plasticity, can make a large high resolution CMOS sensor is increased and the cost is not much. Compared with respect to the stagnation of CCD and CMOS as a novelty show a vigorous vitality. As a core component of a digital camera, CMOS light sensor has been gradually replaced by CCD sensor is the trend, and hopefully become the mainstream in the near future, the light sensor. Factor for image sensitive devices for digital cameras, video imaging of light-sensitive device has two main factors: First, the area of ??light-sensitive devices; second photosensitive device color depth. Photosensitive device area is larger, the larger image under the same conditions, can record more image detail, the interference between pixels is also small, image quality is better. However, with the stylish compact digital camera in the direction to the development of light-sensitive area of ??the device can only be more and more. In addition to area, the light-sensitive devices, another important indicator is the color depth, that is, the color bit is a binary number with the number of bits to record the three primary colors. Non-professional digital cameras are generally photosensitive device 24, the high point of sampling is 30, while the record is still 24-bit, professional digital camera imaging device is at least 36, and is said to have been 48 the CCD. For 24-bit device, the light-sensitive unit to record the brightness values ??of up to 2 ^ 8 = 256 levels, each primary color with a 8-bit binary numbers that record the color is up to about 16,77 256×256x256 million. For the 36 devices, the light-sensitive unit can record a maximum brightness value of 2 ^ 12 = 4096, each primary color with a 12-bit binary numbers that can record up to the color is about 6.87 billion kinds 4096×4096x4096 . For example, if a subject, the brightness of the brightest parts of the darkest parts of the brightness is 400 times the light-sensitive devices with 24-bit digital camera to shoot, and if part by low light exposure, the brightness is higher than any 256 prepare the site, are overexposed, the level of loss, the formation of bright spots, according to what parts to high light exposure, the brightness of the following parts of a total lack of exposure, if using a light-sensitive devices 36 professional digital camera, it will not such a problem.
1.6.9 flash flash of English, called Flash Light. Flash is one of the ways to enhance the exposure, especially in dark places, playing flash help make the scene brighter. Defects using the flash will appear, for example, characters in the film, the flash of light may be left in the pupil of the eye phenomenon occurs, and then place “red eye” scenario, many camera operators will “eliminate red-eye” on the design of this feature, before opening play in a weak flash of light to the pupil to adapt to, and then run a real flash to avoid red-eye occurs. Middle and low digital cameras usually have three flash modes, auto flash, red-eye reduction flash on and off. High point of the product and then provides “Flash” and even “slow flash” feature.
1.6.10 zoom zoom are two, one is digital zoom; one is the optical zoom. Function and phone, most of them use digital zoom.
1.6.11
digital zoom digital zoom, also known as digital zoom, the English name for the Digital Zoom,best buy coupons Digital zoom digital camera by the processor, each pixel within the image area increases, to achieve the amplification purposes. This approach like the use of image processing software to change the big picture of the area, but the program within the digital camera, the original CCD image sensor on the part of the pixel using the “interpolation” processing means to do zoom on the CCD image sensor pixel interpolation algorithm used to enlarge the picture to the whole picture. Unlike optical zoom, digital zoom is up in the light-sensitive device changes the vertical direction, and gives a zoom effect. In the sensitive area of ??the smaller device, then it will allow users to visually see the local scenery. However, due to no change in focal length, so the image quality is poor compared to normal circumstances. Through the digital zoom, zoom shooting the scene, but its resolution will have decreased to some extent, so the digital zoom is not much practical significance. But Sony unique “smart digital zoom,” said the advanced technology, can make the image even after the digital zoom to maintain a certain clarity.
1.6.12 optical zoom optical zoom
English name for the Optical Zoom, digital cameras rely on the optical zoom lens structures to achieve. Digital camera optical zoom 35mm camera, about the traditional way, that is, moving through the lens to zoom in and out need to take in the scenery, the greater the optical zoom and can shoot the scene the more distant. Optical zoom is through the lens, the location of objects and change the focus of three generated. When the image plane when in the horizontal direction, as shown, visual, and focus will change, beyond the scene becomes clearer, people feel like objects, progressive feel. Cleardigital camera ratingsly, there must be two ways to change the angle, one is to change the lens focal length. Words with photography, which is the optical zoom. Zoom in by changing the relative position of the lens to change the lens focal length. Another is to change the size of the image plane, the image plane of the diagonal length of the current digital photography, which is called digital zoom. In fact digital zoom lens focal length does not change, just by changing the image plane to change the angle of the diagonal angle, resulting in the “equivalent” focal length lens effect. Today optical zoom digital camera mostly in the 2-fold between -5 times, you can put an object closer than 10 meters to 5-3 meters in the past; also have some digital cameras with 10 times optical zoom effect. Home video camera optical zoom of 10 times to 22 times, can be captured more clearly the things outside of 70 meters. Increasing magnification using video cameras to increase the optical zoom. If the optical zoom is not enough, we can add a multiplier front of the camera lens, it is calculated that a 2 times the Teleconverter, set in an original with 4x optical zoom digital camera, then that digital camera optical zoom from 1 times 2 times 3 times 4 times to 2 times, 4 times, 6 times and 8 times, that is a multiple of Teleconverters and obtained by multiplying the optical zoom.
1.6.13 burst of English, called multi-shot continuous shooting, data transfer time by saving to capture the photo opportunity. Burst mode data into a digital camera by the internal high-speed memory (cache), rather than transferring data to the memory card can be taken in rapid succession, multiple photos. As digital camera to go through photoelectric conversion, a / d conversion process and media records, includcctv dvring records, whether or conversion takes time, especially to spend more time recording. Therefore, all digital cameras are not fast continuous shooting speed. Continuous frame as the unit generally, it seems like the movie film, each frame represents a picture of the number of frames per second to capture more, faster continuous shooting function. Currently, the fastest digital camera in continuous shooting speed of 7 frames / sec, and continuous shooting must be a few seconds after 3 seconds in order to continue shooting. Of course, the continuous shooting speed for sports photography by photographers and a good indicator of who is important to note, but do not have to consider the situation of ordinary photography. In general, burst capture the photo, resolution and quality will be reduced. Some digital cameras can be selected in the multi-shot, low-resolution photos taken, shooting can be speeded up, on the contrary, resolution, continuous shooting speed of large photos will be relatively slow. By Burst mode, just tap the button to continuous shooting, continuous action vividly recorded.
1.6.14 White Balance Auto White Balance
English name for the White Balance. Object color generated due to projected changes in light color in different light situations capture the photos have different color temperature. Such as tungsten (light bulb) lighting of the environment, the picture may be yellowish, in general, CCD is no way the same as the human eye will automatically correct the light changes. That no matter how light the white balance, digital cameras default to “white”, that is, let him recognize the white and other colors in the color balance of light colors. Color is essentially the interpretation of light, in normal light, the white stuff looks like the light in the dark looks may not be white, as well as fluorescent “white” is also “non-white.” For all this if we can adjust the white balance, then the resulting photo will be able to correct the “white” as the color to restore the other colors. Now most of the commercial-grade digital cameras offer white balance adjustment function. As mentioned earlier, closely related to white balance with the ambient light, thus, start the white balance function should be restricted to use flash, or changes in ambient light will make the failure or interfere with the normal white balance white balance.
1.6.15
video capture video capture feature is a digital camera with video capture function. Unlike DV (digital camera), digital camera video files can only be stored in the memory card inside, due to the limited memory space, so the quality of the video file with the size of the weak. Taken using a mobile phone video, typically using 128 × 96 and 176 × 144 size of the two resolutions, according to the phone memory may be, relatively speaking, support the expansion of mobile phones to take video store a long time.
2 cell phone camera of the camera principle
2.1 Analysis
OmniVision Technologies Co., Ltd. is the world market for large-volume single-chip video camera solutions for suppliers. Its unique CameraChips TM technology, OmniVision integrates image acquisition and processing functions on a single chip, only one lens to provide a complete imaging solutions. Unlike other multi-chip image sensor solutions, OmniVision CameraChips TM does not require an external processor that can output high-quality still and video images. To be lower power consumption, smaller, more peripheral functions, lower prices than competitors solutions. Our intellectual property rights, including increased sensitivity, extended dynamic range, improved image resolution, significantly reducing noise and proprietary technology. Reduce noise to further improve the sensitivity, but also extends the OmniVision CameraChips TM can be applied to the occasion.
SCCB is OmnVision developed a two-way three-wire synchronous serial bus, wire line interface has enabled SCCB_E, is the serial clock signal bus SIO_C, serial data signal bus SIO_D. SCCB to achieve complete control bus functions is to rely on SCCE, SIO_C, SIO_D three bus status and the level of mutual cooperation between the three implemented. Control bus under the following conditions: when the SCCE a high to low, data transfer begins. When the SCCE has low conversion is high, the data transfer is complete. In order to avoid sending useless information bits, respectively, before the start of the transmission, the transmission is set after the end of the SIO_D high. During data transfer, SCCE remain low, SIO_D the transmission of data by SIO_C control. When SIO_C is low, SIO_D on the data available, SIO_D data for the stable state, SIO_C there is a positive pulse each, will send a data.
SCCB_E active low, if the ground, then SIO_C, SIO_D way of working is very similar to the I2C bus. With the I2C bus, as in the SCCB bus master device sends a byte, the data line from the equipment needs to be pulled down as a response signal SIO_D (ACK) back to the master to that sent successfully. It should be noted that CMOS devices can withstand the sink very low, so connected to the clock line SIO_C, data cable SIO_D pullup resistor should be between 3 ~ 5 kΩ, and for the master device sends the parameters has been completed, the immediate release of the data required to ensure that it is in line SIO_D suspended state, that is the main equipment while stocks immediately after the enforcement of a one byte instruction, so that a read data signal line SIO_D operation.
