CN117915068A

CN117915068A - HDMI test method based on electronic switch

Info

Publication number: CN117915068A
Application number: CN202311704199.1A
Authority: CN
Inventors: 曾志; 蔡欣华; 吕俊
Original assignee: Shanghai Pance Information Technology Co ltd
Current assignee: Shanghai Pance Information Technology Co ltd
Priority date: 2023-12-12
Filing date: 2023-12-12
Publication date: 2024-04-19

Abstract

The invention discloses an HDMI test method based on an electronic switch, which comprises the following steps: s1) establishing physical connection between a multichannel high-bandwidth oscilloscope and test equipment, and configuring an electronic switch to switch different signal channels; s2) sequentially selecting a plurality of high-speed signal lines on the HDMI through an electronic switch, and connecting the high-speed signal lines to corresponding channels of an oscilloscope for signal acquisition; s3) measuring and calculating the following signal parameters from the acquired signal waveforms: single-ended and differential properties, offset between signals, offset between signal pairs, single-ended voltage, differential voltage, and eye jitter of differential signals; s4) provides a 3.3V termination voltage through an external power supply or an oscilloscope channel. The invention ensures the continuity and accuracy of signal acquisition, improves the accuracy and reliability of test results, and can evaluate the performance of the HDMI interface more accurately.

Description

HDMI test method based on electronic switch

Technical Field

The present invention relates to an HDMI test method, and more particularly, to an HDMI test method based on an electronic switch.

Background

HDMI (high-Definition Multimedia Interface) is widely used as a digital interface for high-definition video and audio transmission, and the quality of signal transmission directly affects the final display effect. With the popularization of high definition and ultra-high definition content, the requirements for testing the HDMI interface are also higher and higher, and an efficient and accurate testing method is urgently needed to ensure the performance of the HDMI interface.

The traditional HDMI signal testing method mainly relies on manual operation, and a common oscilloscope is used for measuring signal lines on an interface one by one. With the increase of test demands, some automatic test devices are also available on the market, and the devices are usually integrated with special test software and hardware, so that the signal acquisition and analysis processes can be automatically completed, and the test efficiency is improved. However, these devices are often expensive, and are highly specialized and inflexible.

In recent years, with the development of electronic technology, electronic switches have been introduced into the testing of HDMI signals due to their ability to rapidly switch signal channels. Through combining the electronic switch with the oscilloscope, the quick switching and continuous acquisition of a plurality of signal lines on the HDMI interface can be realized, and the testing efficiency is greatly improved. However, existing electronic switch-based testing methods still have some problems. Firstly, the signal switching time is too long, which may cause the discontinuity of signal acquisition and affect the accuracy of the test result; secondly, the existing method has fewer parameters for signal analysis, and cannot comprehensively evaluate the performance of the HDMI; finally, failure of some test methods to provide a stable Termination voltage may affect the signal output quality of the device under test.

Therefore, the method is necessary to comprehensively optimize and improve the defects of the conventional HDMI signal testing method based on the electronic switch, provides a more efficient and accurate testing method, and has important practical application value and popularization prospect.

Disclosure of Invention

The technical problem to be solved by the invention is to provide the HDMI test method based on the electronic switch, which ensures the continuity and accuracy of signal acquisition, improves the accuracy and reliability of test results and can evaluate the performance of the HDMI interface more accurately.

The technical scheme adopted for solving the technical problems is to provide an HDMI test method based on an electronic switch, which comprises the following steps: s1) establishing physical connection between a multichannel high-bandwidth oscilloscope and test equipment, and configuring an electronic switch to switch different signal channels; s2) sequentially selecting a plurality of high-speed signal lines on the HDMI through an electronic switch, and connecting the high-speed signal lines to corresponding channels of an oscilloscope for signal acquisition; s3) measuring and calculating the following signal parameters from the acquired signal waveforms: single-ended and differential properties, offset between signals, offset between signal pairs, single-ended voltage, differential voltage, and eye jitter of differential signals; s4) provides a 3.3V termination voltage through an external power supply or an oscilloscope channel.

Further, in the step S1, the oscilloscope channels are connected with the electronic switch through cables, and the electronic switch is configured, so that each channel of the oscilloscope is connected with the electronic switch through one cable.

Further, the multi-channel high-bandwidth oscilloscope is a 4-channel high-bandwidth oscilloscope, and 8 high-speed signal lines on the HDMI interface are sequentially selected through the configured electronic switch.

Further, the step S2 collects a signal waveform for a certain period of time for each signal line, and controls the sampling frequency to be at least twice the signal frequency.

Further, the step S3 obtains the eye jitter value by calculating standard deviations of the differential signals at different time points, and the standard deviation is calculated according to the following formula:

σ_ΔV＝sqrt((1/N)*sum((ΔV[n]-mean(ΔV))^2))；

Where DeltaV [ N ] represents the differential voltage at the nth sample point, mean (DeltaV) represents the average value of the differential voltage over the time window, and N represents the total number of sample points.

Further, the external power supply in the step S4 has overcurrent and short-circuit protection functions, and the fluctuation range is controlled within ±0.05v.

Compared with the prior art, the invention has the following beneficial effects: the HDMI test method based on the electronic switch, provided by the invention, improves the test efficiency and accuracy and ensures the reliability of the test result. Specifically, the technical problems solved by the invention and the technical effects achieved are as follows:

1. In the traditional HDMI signal testing method, due to the fact that manual operation is relied on or the switching speed of equipment is low, continuous and rapid collection of a plurality of high-speed signal lines on an HDMI interface is difficult to achieve. The acquired signal data may be broken, so that the real performance of the tested equipment cannot be accurately reflected, and the reliability of the test result is affected. According to the invention, by introducing the electronic switch and optimizing the switching time, the rapid and continuous acquisition of a plurality of signal lines on the HDMI is realized, so that the continuity and accuracy of signal acquisition are improved.

2. Comprehensive signal analysis, namely, the conventional HDMI signal testing method usually only focuses on single or few parameters, and cannot comprehensively evaluate the performance of an HDMI interface. The one-sided test may miss some key performance indexes, resulting in incomplete test results and failure to accurately judge the performance of the tested equipment. According to the invention, measurement of various parameters including single-ended and differential properties, offset between signals, offset between signal pairs, single-ended voltage, differential voltage, eye pattern jitter of differential signals and the like are introduced in a signal analysis stage, and the performance of the HDMI interface is more accurately evaluated through comprehensive signal analysis.

3. Providing a stable Termination voltage, namely providing the stable Termination voltage in the process of testing the HDMI interface is an important condition for ensuring that tested equipment can work normally and output accurate signals. In the conventional test method, the Termination voltage is often provided by an external power supply, which may affect the accuracy of the test result due to the instability of the power supply. The invention provides stable 3.3V Termination voltage through the internal or external power supply of the oscilloscope channel, ensures that the tested equipment can correctly output signals in the simulated actual working environment, and improves the accuracy and reliability of the test result.

Drawings

Fig. 1 is a flowchart of an HDMI test based on an electronic switch according to the present invention.

Detailed Description

The invention is further described below with reference to the drawings and examples.

Referring to fig. 1, the HDMI testing method based on an electronic switch provided by the present invention includes the following steps:

s1) establishing physical connection between a multichannel high-bandwidth oscilloscope and test equipment, and configuring an electronic switch to switch different signal channels;

s2) sequentially selecting a plurality of high-speed signal lines on the HDMI through an electronic switch, and connecting the high-speed signal lines to corresponding channels of an oscilloscope for signal acquisition;

S3) measuring and calculating the following signal parameters from the acquired signal waveforms: single-ended and differential properties, offset between signals, offset between signal pairs, single-ended voltage, differential voltage, and eye jitter of differential signals;

S4) provides a 3.3V termination voltage through an external power supply or an oscilloscope channel.

The present invention exhibits significant advantages, particularly in the following aspects:

1. test efficiency is improved: in the existing optimal technology, testing a high-speed HDMI interface typically requires manually switching test probes or using slower switching equipment, which not only consumes a lot of manual time, but also increases errors in the testing process. The invention adopts a quick electronic switching technology, realizes quick and automatic switching of a plurality of high-speed signal lines on the HDMI interface, and greatly improves the testing efficiency. The time loss of manual operation is almost eliminated in the test process, and the high-speed test is ensured.

2. The test accuracy is improved: the prior art often ignores details in the signal acquisition and analysis links, such as offset between signals, eye jitter of differential signals, etc., which may lead to inaccuracy in the test results. According to the invention, a comprehensive signal analysis method is introduced in the signal analysis stage, so that multiple parameters such as single-ended and differential properties, offset between signals, offset between signal pairs, single-ended voltage, differential voltage, eye pattern jitter of differential signals and the like are comprehensively measured, and the comprehensiveness and accuracy of test results are ensured.

3. Optimizing the test environment: in the prior art, the supply of Termination voltage is often unstable and may be limited by external disturbances or by the performance of the device itself. According to the invention, the stable 3.3V Termination voltage is provided by the internal or external power supply of the oscilloscope channel, so that the stability of the Termination voltage is ensured, and the simulation accuracy of the test environment is improved. The method solves the problem that the test result is inaccurate due to unstable power supply in the traditional method, and improves the reliability of the test result.

The main steps of the present invention will be further described below.

1. Connection and configuration

In the HDMI high-efficiency test method of the present invention, it is first necessary to establish physical connection between test devices and to perform correct configuration on the test devices. This step is a critical loop in the whole test flow, and its correctness directly affects the accuracy and efficiency of the test.

Physical connection:

the invention uses 4 high-quality cables to connect the 4-channel high-bandwidth oscilloscope with the electronic switch. The oscilloscope is denoted here by P, and its channels are denoted by c_i (i=1, 2,3, 4), respectively. The electronic switch is denoted S and the cable is denoted L. Thus, the connection relationship can be represented by P (C_i) -L-S, meaning that each channel of the oscilloscope is connected to the electronic switch by a cable. The quality of the cable has a direct impact on the transmission quality of the signal, so the present invention needs to ensure that the cable has sufficient bandwidth and good shielding effect to minimize loss and interference of the signal during transmission.

An electronic switch configuration:

The electronic switch is used for rapidly switching different signal channels according to control signals, so that a single oscilloscope can measure up to 8 signal wires. The time of switching the signal channel is denoted by T, the actual value of which needs to be determined according to the test requirements and the performance of the electronic switch, but theoretically the value should be much smaller than the period of the signal to ensure the continuity and accuracy of the signal acquisition. For example, if the HDMI signal frequency tested by the present invention is 1GHz, then the period of the signal is 1ns. To ensure continuity and accuracy of acquisition, the value of T can preferably be controlled on the order of 1ps (1 e-12 s).

The configuration of the electronic switch includes setting parameters such as its operating mode, the source and type of control signals, the switching speed, etc. The setting of these parameters needs to be done according to specific test requirements and the performance of the electronic switch. In the configuration process, the invention also needs to consider the signal integrity, and avoid the distortion of the signal in the switching process caused by improper configuration of the electronic switch.

In general, the connection and configuration in step 1 is the basis in the whole test method, and the purpose of the connection and configuration is to establish a stable and reliable test environment, so as to ensure that accurate and reliable test results can be obtained in the subsequent test steps. This requires the invention to select high quality cables and connectors for physical connection and carefully set parameters according to specific requirements for electronic switch configuration, ensuring signal integrity and accuracy throughout the test.

2. Signal acquisition

After the connection and configuration in step 1 is completed, the invention enters a signal acquisition phase, which is a key step to ensure test accuracy and efficiency. In the step, 8 high-speed signal lines on the HDMI are sequentially selected through the electronic switch, and are connected to corresponding channels of the oscilloscope for signal acquisition.

Signal selection and connection:

The invention uses the electronic switch to sequentially select 8 high-speed signal lines on the HDMI interface. Here, s_i (i=1, 2,3,., 8) is used to denote the 8 signal lines, and P (c_i) is used to denote the channel of the oscilloscope. The electronic switch connects s_i to P (c_i) so that the signal can be transmitted to an oscilloscope for acquisition.

And (3) signal acquisition:

After the signal is transmitted to the oscilloscope, the signal needs to be acquired so as to facilitate subsequent analysis and processing. The time domain waveform of the signal is denoted by V (t), where t denotes time. During the acquisition phase, the invention samples the signal continuously for a certain period of time, which is denoted by t_s. The value of t_s needs to be determined according to the characteristics of the signal and the test requirements, so that the invention can obtain enough signal information in the time.

The sampling frequency f_s is another parameter of interest that represents the number of samples per second. According to the nyquist sampling theorem, in order to be able to accurately restore the signal, f_s should be at least twice the signal frequency. For example, if the HDMI signal frequency tested by the present invention is 1GHz, then F_s should be at least 2GHz.

The result of the sampling is denoted by V_s [ n ], where n is an integer representing the index of the sampling point. Each v_s n corresponds to a signal value V (t_n) at a time t_n. In this way, the invention converts continuous signals into discrete sampling points, which lays a foundation for subsequent signal analysis and processing.

In general, the signal acquisition stage is a crucial step in the overall test flow, which directly relates to the accuracy and reliability of the test results. The invention needs to accurately select the signal line to be tested through the electronic switch, ensures that the setting of the sampling time and the sampling frequency can meet the testing requirement and the characteristics of the signal, and finally obtains enough signal information for subsequent analysis and processing. In this way, the invention not only ensures the high efficiency of the test, but also ensures the accuracy and reliability of the test result.

3. Signal analysis

After the acquisition of the signal is completed, the invention enters a signal analysis stage. The goal of this stage is to extract parameters from the acquired signal waveforms that are critical to testing and evaluating HDMI interface performance. These parameters include, but are not limited to: single ended and differential properties, offset between signals, offset between signal pairs, single ended voltage, differential voltage, eye jitter of differential signals, etc.

Among these parameters, eye jitter of a differential signal is an important performance indicator that reflects the stability and reliability of the signal during transmission. The large eye jitter means that the signal is greatly disturbed in the transmission process, which may cause the misinterpretation of the signal by the receiving end, thereby affecting the performance of the whole communication system.

In order to accurately measure the eye jitter of the differential signal, the invention can calculate the standard deviation of the differential signal at different time points. Specifically, the present invention first defines a differential voltage Δv, which is the voltage difference across the differential signal. Next, the present invention calculates the standard deviation σ_Δv of Δv within a certain time window.

The calculation formula of the standard deviation is as follows:

σ_ΔV＝sqrt((1/N)*sum((ΔV[n]-mean(ΔV))^2))

here, Δv [ N ] represents a differential voltage at an nth sampling point, mean (Δv) represents an average value of the differential voltage over the entire time window, and N represents the total number of sampling points.

Through the formula, the jitter condition of the differential signal in a given time window can be obtained, so that the stability and reliability of the signal can be evaluated. Notably, this calculation process needs to be performed on each differential signal pair to ensure that a comprehensive and accurate test result is obtained.

In general, the signal analysis stage is a key step in ensuring accuracy of HDMI interface performance assessment. Through detailed measurement and analysis of various parameters, the invention can comprehensively understand the transmission characteristics of signals, discover and solve possible problems in time, and ensure the stable and reliable operation of the whole communication system. In this way, the invention not only ensures the quality of the product, but also provides a better and reliable use experience for the user.

4. Providing Termination

In high-speed signal testing, providing a correct Termination resistor (Termination) is a critical step, which ensures signal integrity on the transmission line, reduces signal distortion caused by reflections, and thus ensures signal quality. In the process of efficiently testing an HDMI interface, the present invention generally requires that a suitable voltage be provided at the end of the interface to simulate termination resistance.

The invention herein uses V_t to represent the termination voltage, which should be stable around 3.3V. The 3.3V is selected as the termination voltage because it is a voltage level common to many digital devices and is compatible with a variety of types of HDMI devices. Providing a stable v_t is critical to obtaining accurate and reliable test results.

In a specific implementation, the present invention may provide V_t through an external power supply or within an oscilloscope channel. If an external power supply is selected, the invention needs to ensure that the stability and the precision of the output voltage of the power supply meet the test requirements. In general, the output voltage of the power supply should have high accuracy, and the fluctuation range is controlled within ±0.05v. In addition, the external power supply has overcurrent and short-circuit protection functions so as to prevent accidents from damaging the tested equipment or the testing system.

If V_t is selected to be provided through the inside of the oscilloscope channel, relevant parameters of the oscilloscope need to be configured, so that the output voltage of the oscilloscope is ensured to be stabilized around 3.3V. Typically, this requires setup through the user interface or programming interface of the oscilloscope. When the oscilloscope is arranged, the operation guide of the oscilloscope needs to be known and familiar in detail, so that the accuracy of configuration is ensured.

The voltage output by the voltage meter is monitored in real time by using the high-precision voltage meter to ensure the stability of the voltage meter no matter the voltage meter is provided with V_t through an external power supply or the inside of an oscilloscope channel. During the test, if any abnormal fluctuation of V_t is found, the test should be immediately paused, the fault is checked and eliminated, and then the process is continued.

By providing stable V_t, the invention can simulate the electrical conditions in the actual working environment and ensure that the tested equipment can correctly output signals. This has an important meaning for accurately evaluating the performance of the HDMI interface, ensuring the reliability of data transmission. Providing proper Termination is a key ring in achieving efficient and accurate testing throughout the test flow.

Through the series of steps, the invention solves the problems of low testing efficiency and low accuracy of the HDMI signal of the high-speed digital interface in the prior art. Through a precisely designed test system, the invention realizes the rapid and accurate measurement of a plurality of high-speed signal lines of the HDMI interface, improves the test efficiency, and ensures the accuracy and reliability of the test result. In the connection and configuration stage, the invention adopts a mode of combining the 4-channel high-bandwidth oscilloscope with the electronic switch, connects the oscilloscope channel with the electronic switch through a cable, and configures the electronic switch to ensure that the electronic switch can rapidly switch different signal channels according to control signals. This configuration ensures continuity and accuracy in the signal acquisition process. In the signal acquisition stage, 8 high-speed signal lines on the HDMI interface are sequentially gated through the electronic switch and connected to corresponding channels of the oscilloscope for acquisition. The setting of the sampling frequency meets the Nyquist sampling theorem, and the accuracy of signal acquisition is ensured. In the signal analysis stage, the invention analyzes the acquired signal waveform in detail, including measuring various parameters such as single-ended and differential properties, offset between signals, single-ended voltage, differential voltage, eye pattern jitter of differential signals, and the like, and comprehensively evaluates the performance and signal quality of the HDMI interface. Finally, in the Termination providing stage, the invention provides stable 3.3V Termination voltage through the external power supply or the inside of an oscilloscope channel, so as to ensure that tested equipment can correctly output signals in an analog actual working environment, thereby obtaining accurate and reliable test results. In summary, the present invention provides a quick, accurate and efficient HDMI signal testing method, which has important significance for improving efficiency and accuracy of high-speed digital interface testing.

While the invention has been described with reference to the preferred embodiments, it is not intended to limit the invention thereto, and it is to be understood that other modifications and improvements may be made by those skilled in the art without departing from the spirit and scope of the invention, which is therefore defined by the appended claims.

Claims

1. An HDMI test method based on an electronic switch is characterized by comprising the following steps:

2. The HDMI switch-based test method of claim 1, wherein step S1 connects the oscilloscope channels to the electronic switch via a cable, and configures the electronic switch such that each channel of the oscilloscope is connected to the electronic switch via a cable.

3. The HDMI test method of claim 2, wherein the multi-channel high bandwidth oscilloscope is a 4-channel high bandwidth oscilloscope, and 8 high speed signal lines on the HDMI interface are sequentially selected by the configured electronic switch.

4. The HDMI test method based on an electronic switch according to claim 1, wherein the step S2 collects a signal waveform for a certain period of time for each signal line and controls the sampling frequency to be at least twice the signal frequency.

5. The HDMI test method based on electronic switch of claim 1, wherein the step S3 obtains the eye jitter value by calculating standard deviations of the differential signals at different time points, and the standard deviation is calculated by the formula:

σ_ΔV＝sqrt((1/N)*sum((ΔV[n]-mean(ΔV))^2))；

6. The HDMI test method based on electronic switch of claim 1, wherein the external power supply in step S4 has overcurrent and short-circuit protection functions, and the fluctuation range is controlled within ±0.05v.