The most common stereo headphones are divided into three layers, and the standard distribution is "red and white on the left and right" (from
the end to the root, they are the left channel, the right channel, and the ground wire) , among which the left channel usually uses red wire,
the right channel usually uses white).
The most common ones are silver-white and copper-yellow. The silver is copper plated with silver, and the copper-yellow is
copper. Since silver is more stable and electronically engineered than copper, plating copper with silver can upgrade the user experience of using the plug device.
USB is a commonly used PC interface. It has only 4 wires, two for power and two for signals.
Therefore, the signals are transmitted serially, and the USB interface is also called serial. By the way, the speed of usb2.0 can reach 480Mbps. It can meet various industrial and civilian needs. The output voltage and current of the USB interface are: 5V 500mA. There is actually an error, and the maximum cannot exceed /-0.2V, which is
4.8 -5.2V. The four wires of the USB interface are generally allocated as follows. What needs to be noted
Be sure not to reverse the positive and negative poles, otherwise the USB device or the south bridge core of the computer will be burned
Film. Black wire: gnd Red wire: vcc Green wire: data White wire: data-
USB interface definition color
The general arrangement is: red, white, green and black from left to right
p>
Definition:
Red-USB power supply: marked with -VCC, Power, 5V, 5VSB
White-USB data cable: (negative) -DATA-, USBD-, PD-, USBDT-
Green-USB data cable: (positive)-DATA, USBD, PD, USBDT
Black-Ground wire: GND, Ground
There are two types of USB interface cables. Usually we connect it to the computer interface
One end is called the "A" connector, and the connector that connects the peripherals is called "B" "Connector (usually
peripherals have built-in USB data cables and only include the "A" connector connected to the computer).
USB interface is an increasingly popular interface method, because the characteristics of USB interface
are outstanding: fast speed, good compatibility, It does not occupy interrupts, can be connected in series, supports hot plugging, etc., so now many printers, scanners, digital cameras, digital still cameras, MP3 players, MODEMs, etc. have begun to use USB as the interface Mode, the USB interface definition is also very simple:
1 5V
2 DATA data
3 DATA- data-
4 GND ground
Motherboards generally integrate two serial ports, but Windows can provide up to 8 serial port resources for hardware settings (numbered COM1 to COM8). Although its I/O address Not the same, but
The total number only occupies two IRQs (1, 3, 5, and 7 share IRQ4, and 2, 4, 6, and 8 share IRQ3),
Usually we commonly use the four ports COM1~COM4. We often encounter
this problem in use - if a serial mouse or other peripherals are installed on COM1, other devices such as Modem cannot be installed on COM3. Hardware, this is because IRQ setting conflict
cannot work. At this time, players can install additional peripherals on COM2 or 4.
Standard serial ports can reach a maximum data transmission speed of 115Kbps, while some enhanced serial ports such as ESP (Enhanced Serial Port) and Super
ESP (Super Enhanced Serial Port, Super Enhanced Serial Port) can achieve a data transmission rate of
460Kbps.
The serial port is one of the main external interfaces of the computer. Through the nine-pin serial port, there are many connected devices
such as serial mouse, MODEM, handwriting pad, etc.
The schematic diagram of the nine-pin serial port is as above.
The definition of each pin is as follows:
1 DCD carrier detection
2 RXD receiving data
3 TXD sending data
4 DTR data terminal ready
5 SG signal ground
6 DSR data ready
7 RTS Request to send
8 CTS Clear to send
9 RI Ringing indication
The monitor is of course a very important device. The monitor uses a 15-pin connector.
Because the monitor is a relatively independent electronic device, its connector definition also has many professional parts. The specific pin definitions are as follows:
RJ45 type network cable plug, also known as crystal plug, is made of eight cores and is widely used in network equipment between LAN and ADSL broadband Internet users (called Category 5 cable or twisted pair line) connection
. In specific applications, there are two connection methods (line sequences) for RJ45 plugs and network cables, which are called T568A line sequence (Figure 1) and T568B line sequence (Figure 2) respectively.
The identification method of the pin number of the RJ45 type network cable plug is: hold the plug in hand, there are 8 small platings,
One end of the gold piece is upward, and there is a large rectangular opening for the network cable to be inserted. With one end facing downwards, face the one without the thin
long plastic bayonet toward your eyes, starting from the first small gold-plated piece on the left
which is the first foot, The 2nd foot,...,8th foot.
This connection method is used when network equipment needs to be cross-connected. The so-called cross-over refers to that one end and the other end of the network cable
are connected in different ways to the RJ45 network cable plug. One end presses T568A wire sequence
is connected (Picture 1), and the other end is connected according to T568B wire sequence (Picture 2), that is, there are several network cables at the other end that are crossed first. Connected to the RJ45 plug, the applicable connection situations are:
Applicable scope of T568B line sequence
1. Direct cable interconnection
Both sides of the network cable Both terminals are connected according to T568B
The original parallel port design is for one-way data transmission, which means that data can only be input or output at a certain time.
Later, IBM developed a two-way parallel port technology called SPP (Standard
Parallel Port), which can realize the simultaneous input and output of data, so that The original semi-interactive parallel port became a true two-way interactive parallel port. Intel,
Xircom and Zenith jointly launched EPP (Enhanced Parallel Port,
Enhanced Parallel Port in 1991) Parallel port), allowing the transmission of larger capacity data (500~1000byte/s), which is mainly aimed at non-printer devices that require higher data transmission speeds, such as storage devices; tight
Following the launch of EPP, in 1992 Microsoft and HP jointly launched a new parallel port standard called ECP (Extended
Capabilities Port,). Unlike EPP, ECP is specifically for
A standard developed for printers; IEEE 1284, released in 1994, covers both EPP and ECP
but requires both the operating system and hardware to support the standard, which is difficult for current hardware
Words are no longer a problem. The parallel ports we currently use support the two standards of EPP and ECP, and we can set the working mode of the parallel port ourselves in CMOS.
The parallel port is a very important external device interface of the computer. The most commonly used device
to connect is the printer. In addition, there are many models of scanners that also use the parallel port. Come
connected to the computer. The parallel port is also 25-pin. Different from the 25-pin serial port, the parallel port has 25 holes, so it is often called "female", while the serial port is often called "male". The pin definition of the parallel port
is as follows:
The IEEE1394 interface is also called the Frie wire interface (commonly known as "FireWire" in Chinese). It has high data transmission rate
and the IEEE1394a interface It can provide 100Mbps, 200Mbps, 400Mbps and other transmission formats
; IEEE1394b can provide 800Mbps data transmission rate
The full name of eSATA is External Serial ATA, and eSATA is actually SATA
The external expansion specification of the interface, the transmission speed is exactly the same as SATA. eSATA can provide a maximum transmission speed of 3Gb/s, which is much higher than USB2.0 and IEEE1394. Currently, many desktop motherboards already provide eSATA interfaces.
USB PLUS is an interface specification, it can be said that it is not a real "USB" interface, because it is based on the eSATA interface, or we can say It is
the eSATA interface, but Patriot named it USB
PLUS for publicity or unified naming. We know that the transmission speed of the eSATA interface is much greater than that of the USB2.0 interface, but
it cannot power itself, and mobile devices cannot use the eSATA interface. However, Patriot solved this problem by adding a power supply function to the traditional eSATA interface. Users can then use the eSATA interface in the same way as a USB interface.
The DVI interface has a variety of specifications, divided into DVI-A, DVI-D and DVI-I. It is based on Silicon
Image's PanalLink interface technology and is based on TMDS (Transition
Minimized Differential Signaling, minimized transmission of differential signals) electronic protocol
as the basic electrical connection. TMDS is a differential signaling mechanism that encodes pixel data and transmits it over a serial connection. The digital signal generated by the graphics card is encoded by the transmitter according to the TMDS protocol and sent to the receiver through the TMDS channel. After decoding, it is sent to the digital display device. A DVI display system includes a transmitter and a receiver. The transmitter is the source of the signal. It can be built into the graphics card chip or appear as an additional chip on the graphics card PCB. The receiver is on the monitor. A circuit that can accept digital signals,
decode them and pass them to the digital display circuit. Through the two, the signals sent by the graphics card become
images on the monitor. elephant.
As we have mentioned before, DVI is also divided into several specifications. Among them, DVI-A is actually
a VGA interface standard. It is just a new one. The current DVI interfaces are mainly DVI-D
and DVI-I, and these two specifications are further divided into "dual channel" and "single channel"
Type, what we usually see are single-channel versions. The cost of the dual-channel version is very high, so only some professional equipment has it.
Distinguish between different DVI standards
Among common DVI interfaces, the DVI-D interface can only receive digital signals, and there are only
3 rows and 8 columns** *24 pins, one of which is empty in the upper right corner. Not compatible with analog letters
.
The DVI-I interface is compatible with both analog and digital signals.
Fortunately, analog compatibility does not mean that the D-Sub interface with analog signals can be connected to the DVI-I interface, but it must be used through a conversion connector. Generally, Graphics cards using this interface will have related
conversion connectors.
The difference between 18-pin and 24-pin DVI
When buying an LCD monitor, we may find that there are 18-pin and 24-pin DVI
, some people say that 18-pin DVI is a simplified version, and its performance is much worse than 24-pin. Others say that 24-pin DVI just has more ground wires and there is no difference at all. What are the facts
?
We have mentioned to you before that among the different specifications of DVI, they are divided into "dual
channels" There are two types: "single channel". In fact, the 18-pin and 24-pin are the differences between the two types
. The 18-pin DVI is a single channel, while the 24-pin is a dual channel. In other words, the 18-pin DVI transmission rate is only half of that of the 24-pin, which is 165MHz. In terms of screen display,
single-channel DVI supports exactly the same resolution as dual-channel, but the refresh rate is only about half of that of dual-
channels, which will cause a drop in display quality. decline. Generally speaking, the maximum refresh rate of a single-channel DVI interface can only support 1920 1080 60hz or 1600 1200 60hz.
That is, the existing 23-inch widescreen monitor and 20-inch For normal display of an ordinary ratio monitor, any higher ratio will cause the display effect to decline.
HDMI Type A socket.
The HDMI specification specifies three HDMI connectors, which are:
Pin Pin definition
Test specification
For specification details of HDMI test specification, please refer to: "HDMI Conformance Test Specification 1.1",
"HDMI Specification 1.1", "HDCP Specification 1.1";
1. HDMI output compatibility test:
1. Compatibility with HDMI interface TV: transmit audio and video at the same time;
2. Compatibility with DVI interface TV Performance: only transmits video;
3. Compatibility with the power amplifier of the HDMI interface, only transmits audio
Judgment criteria: The audio that can be transmitted by the HDMI interface supports "anything that can be transmitted through S/ PDIF
output compressed digital audio" and "2/6/8 channel, 32-192KHZ sampling rate uncompressed digital audio", can output "I2S (one A digital transmission interface with better time difference performance
than S/PDIF, suitable for short-distance communication) and SPDIF audio; it can always obtain CD's
audio quality; HDMI interface Videos that can be transmitted support "HD 1080I", "HD
720P", "Normal Interlaced" and "Normal Progressive" (currently we do not support the latter two),
At the same time Supports NTSC and PAL TV standards; can automatically output "YUV" or "RGB" encoded video format according to the video status that the receiving end can accept:
2.
HDMI port plug-in and pull-out reliability test:
1. Interface hot-plug reliability: When both the disc drive and the receiving end are working, plug and pull out the HDMI interface. Whether the equipment is working properly, and whether the audio and video functions of HDMI output are normal;
2. ESD test
3. Interface plug-in life test: multiple plug-in and plug-out life tests Unplug the HDMI interface and test the life of the HDMI interface; judgment standard; during hot plugging, the receiving end can normally output HDMI audio and video signals, and the source end system must still work normally; The interface plug-in and unplug life needs to be at least 5,000 times;
3. Reliability test of HDMI output:
1. Source output drive capability test;
2. Attenuation characteristic test of connecting cable;
3. High frequency And the reliability of large-capacity data transmission;
Judgment criteria: the longest transmission is 30 meters, ensuring normal sound and image; large-capacity DVD
(multi-subtitle, multi-channel) disc playback The smoothness of the picture;
4. Whether the HDMI output is normal when turning on or in standby.
Four. Testing standards for HDMI cables and interfaces:
Please refer to the testing standards of HDMI interface and cable suppliers;
5. HDMI port output test under abnormal working conditions:
1. High and low temperature conditions;
2. High and low voltage conditions;
3. Long-term working conditions;
Judgment criteria: For specific parameters of temperature, voltage and working time, refer to ordinary disc players;
In these states, the audio and video functions of the HDMI interface are required to work properly;
Six. HDMI output port function test:
1. The HDMI port supports 1080I, 720P high-definition format video output;
2. The HDMI port supports various compressed and uncompressed digital audio outputs;
3. Automatically detect the screen ratio of the receiving device; judgment standard: under the same film source,
HDMI high-definition output image effect should be "clearer" than CVBS and ordinary color difference. No flicker,
the details are more expressive and the colors are more realistic" (you can use high-definition JPEG pictures or
DVD effect demonstration discs to demonstrate); if you accept the TV The device can decode the digital audio signal output by HDMI, and the receiving end should have sound output; the HDMI output end can automatically adjust the output aspect ratio to suit the receiving device.
Audio and video test solution
HDMI testing includes video testing and audio testing.
Video test:
The HDMI conformance test standard recommends using Quantum Data 882 to conduct a series of
protocol tests.
Audio test: The HDMI audio test standard recommends using AudioPrecision’s
APX585 for testing.
AP Company is the standard instrument in the audio testing industry. It is the designated audio analyzer certified by Dobly,
DTS, and Miscrosoft DTM.
The first choice to explain the difference between A card and N card is Nvdia's The GPU does not have an integrated audio
processing unit, so various HDMI graphics card manufacturers are trying to save the country by setting up an audio
audio input interface on the graphics card. You must manually connect the motherboard and graphics card before use. previous data line.
ATI's GPU does not have this problem.
Take the Colorful graphics card as an example.
The audio on the N card is introduced through the SPDIF IN interface. On the integrated sound card motherboard
or independent sound card generally has a digital audio output interface SPDIF OUT, use the one provided with the graphics card
Connect the audio cables. Only in this way can HDMI have audio signal output, which means that if your Nvdia graphics card does not have SPDIF IN, then you have to connect the speaker to the computer.
Software settings 1. NVIDIA independent graphics card
Step 1: Install the HD Audio patch of Microsoft KB888111 and the corresponding sound card driver
program.
Step 2: Select "SPDIF Device Output
in "Control Panel → Sound Audio Devices".
Step 3: Install the ForceWare driver for the NVIDIA graphics card, and then open it in advanced mode
NVIDIA Control Panel, enter the "Video and TV → Change Signal or HD Format" option,
At this point you can see that the flat-panel TV connected to the computer has been detected by the system (Figure 2).
Click on its icon and set the corresponding video resolution according to the specific situation of the TV. Yes (Figure
3), for example, set to Full HD 1080P mode
If the resolution of some TVs is special, we can also go to "Display→Manage Auto"
Edit and create a new resolution mode in the “Define Resolution” menu (Figure 4). Finally, set the dual-head output mode of the graphics card. NVIDIA graphics cards generally provide the following modes: dual-screen display (Dual View), horizontal span, vertical span, copy, etc. , it is recommended to use
Dual View mode. At this time, the monitor and flat-panel TV can display different content respectively. For example, use
IE to browse the web on the monitor and watch on the flat-panel TV. High-definition movies
2. AMD discrete graphics card
Step 1: Install the HD Audio patch of Microsoft KB888111.
Step 2: Install the AMD graphics card catalyst driver and Catalyst Control Center (the catalyst driver contains the audio controller driver integrated with the graphics card).
Step 3: Select "ATI HD Audio
rear output" as the audio output device in "Control Panel → Sound Audio Devices" (Figure 5).
Step 4: Open the Catalyst Control Center and select "Extended Desktop Mode" (Figure 6) in the "Multiple Monitor Desktop Mode" menu. This mode is similar to the dual display mode of NVIDIA graphics cards.
Screen display (Dual View), you can set different resolutions on the two monitors and
display different window contents at the same time.
Then set "Extend desktop display overlay" to "In theater mode (full screen)" in the "Video → Theater Mode" menu (see Figure 7 and Figure
8). Finally, set the resolution of the flat-screen TV in the "Display Manager" menu.
Step 5: AMD graphics card also supports progressive scan settings. Selecting "Automatic Detection" here (Figure
9) can appropriately reduce the roughness and roughness in the picture when playing 1080i high-definition video. Drawing phenomenon,
The effect is more obvious especially in high-speed motion pictures.
Latest version
HDMI, the agency responsible for licensing the High Definition Multimedia Interface (HDMI)
Licensing recently announced that the agency will use the new version of the HDMI v1.4 standard Added stereoscopic video
signal support function. The expert group responsible for standard formulation will add a stereoscopic video signal format tentatively named "Top/Bottom" to this standard at a standards meeting next month. The standard will stipulate the transmission protocol for stereoscopic video signals, but the HDMI Licensing
organization also stated that the standard will not make mandatory provisions for the stereoscopic video broadcast signal format for the time being.
They will supplement and modify this part of the content in the future. In addition to stipulating the transmission protocol of stereoscopic video signals, the new specification also adds a data transmission function and adds a dedicated 100Mbps Ethernet connection channel to the HDMI interface. . In addition, the Audio Return channel for transmitting compressed format audio signals has also been added.
There are 5 types of HDMI version 1.4 cables. The standardized identification methods in the future are:
Standard HDMI Cable Chinese specification name: Standard HDMI cable (highest support
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1080/60i)
Standard HDMI Cable with Ethernet Standard Ethernet HDMI Cable
Standard Automotive HDMI Cable Standard Automotive HDMI Cable
High Speed ??HDMI Cable High Speed ??HDMI Cable (supports 1080p, DeepColor, 3D)
High Speed ??HDMI Cable with Ethernet High Speed ??HDMI Cable
Equipment supporting the HDMI v1.4 standard has been launched in 2010 Launched at the CES exhibition
held in early January.
Brands
At present, the famous international and domestic HDMI brands include: Sony, Megalon, Hitachi, Panasonic, Xun
Weibo, Kaiboer, Audier, JIB, Bei Chess, HL, BLUEDE, Akihabara, etc.
The production of HDMI 1.4 plugs and adapter cables has become popular, and Nanfeng in Dongguan can mass-produce them with professional technology.
Frequently Asked Questions and Analysis of HDMI Compatibility Testing:
The vast majority of test customers will more or less perform some tests during the first test
Failed on the project.
In fact, for some electrical performance tests related to chips, such as "Jitter Tolerance", chip manufacturers have already considered how to ensure passing these test items during the chip design stage. Therefore, customers need to pay special attention to some issues related to system design
and the functions designed to cooperate with the test. For example, the source device (Tx) needs to provide the ability to convert HDCP ( Options to turn off and on High Definition Content Protection
etc. The following is a description of some test items based on problems commonly encountered in customer testing. I hope it can help readers avoid these problems in the design stage.
Source test (Tx)
EDID related tests
HDMI source equipment must support the "Enhanced DDC" protocol, i.e. read
When obtaining the EDID information of the receiving device, you can use the segment pointer 0x60 to read the information after the first 256 bytes
. Although most customers now use 256 bytes of EDID information,
During the HDMI test, 4 blocks (128 bytes each) will be detected, which is 512 bytes
Information capabilities. Whether there are multiple blocks of information can be known from the 0x7E address of the EDID content.
When customers test themselves, they often only test the ability to support the first 256 bytes, while ignoring the requirements for segment
pointers.
5V power output
Some customers habitually connect resistors in series to the power output path of the HDMI output port to limit current. But in the HDMI Tx test, a load that draws 55mA current will be connected, and then the output voltage will be tested. The required voltage is between 4.8V and 5.3V. For example
In the example shown in Figure 1, a 10 ohm resistor is connected in series, resulting in an output voltage of, 5
-10x0.055 = 4.45V lt; 4.8V, this Test failed.
Relevant DDC/CEC measurements
When customers deal with the Consumer Electronics Control (CEC) pins of the HDMI port, that is, the
HDMI port’s 13 pin? If its product does not support the CEC function, you can leave this pin unconnected
. However, although the customer's product does not support the CEC function, it still connects this pin
to the general pin of the main processing chip for future expansion. At this time, you need to pay attention to this
There are some limitations on the electrical performance and physical connection of the pins, such as the capacitance needs to be less than 100pF
, otherwise the HDMI test will fail.
Receiver (Rx) test
Issues that should be paid attention to in EDID-related test items
Customers often fail in these EDID test-related tests during the test process. project.
In fact, it is relatively easy to pass these projects if you are familiar with the relevant requirements of the specifications.
For example, relevant specifications require that "Monitor Range Limit Header" and "Monitor Name Header" must be provided in the first 128 bytes of EDID, but if these two items If the content is less than 18 bytes, it needs to end with 0x0A and fill the remaining bytes with 0x20
.
Another problem often encountered in EDID testing is that customers
cannot combine the short video descriptor (SVD) module in EDID with the submitted capability declaration form
(CDF ) is consistent, the formats supported in CDF are not supported in the SVD module of EDID
, or vice versa.
TMDS signal differential impedance matching
Nowadays, most customers will consider the TMDS signal differential impedance matching requirement when designing circuit boards, but often still It will fail in this test because the parasitic capacitance of the ESD protection device chosen by the customer or the ***mode choke used to suppress EMI is too large, causing
causing this test to fail. Nowadays, many suppliers of ESD protection devices for high-speed lines will provide recommended wiring solutions and impedance test charts. Customers can ask these manufacturers to provide relevant information. This test is one of the few test items in the HDMI compatibility test that is related to the hardware circuit. If this test fails, customers often need to change the circuit board design, which will cause delays. Production and time to market.
DDC/CEC channel capacitor voltage test
This test has a very high failure rate. Most of the reasons for failure are that the capacitance of the MOSFET device used by the customer for level conversion is too large. We recommend that the MOSFET device Ciss and Coss used on the DDC channel
It should be below 10pF.
HPD output voltage
Some customers like to use the circuit shown in Figure 2 to utilize the 5V voltage of the HDMI port, and at the same time
use VCCD for the HPD of the HDMI port The pin provides voltage, but this will violate the requirement of the HDMI protocol that when the HDMI 5V input is 0V, the HPD voltage should be greater than 0V and less than 0.4V. The simplest method here is to route the 5V voltage of the HDMI input port directly back to the HPD pin in series with a 1K resistor. Of course, it is still recommended that readers use a simple
transistor switch circuit to control the HPD pin, so that the source device can actively inform whether the downstream device is ready or not. Inform the source device to restart some verification actions, such as HDCP, etc. This can enhance the compatibility of the device.
Video format support
In this test, the video formats supported by all HDMI input ports will be tested
Devices that support 50Hz will be tested for 50Hz ±0.5 (i.e. 49.75Hz and 50.25Hz), and
Devices that support 59.94Hz or 60Hz pair 59.94-0.5 (i.e. 59.64Hz) and 60
0.5 (i.e. 60.3Hz) The ability to support field frequency changes. Customers need to pay attention to these requirements for video format tolerance in software design.