Basic Debugging of LED Displays

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Basic Debugging of LED Displays

Basic Configuration of LED DisplayLED

After the basic configuration of the LED display, it can achieve the full – screen playback of the target screen, such as displaying complete images, videos, and edited programs. Generally, the basic configuration includes the following steps: computer display settings, sending card settings, receiving card settings, and display connection settings.

1. Computer Display Settings

The screen of the LED display is directly output by the computer graphics card. Before configuration, two settings need to be made for the graphics card: copy/output settings and scaling settings.

1.1 Copy/Output Settings of Graphics Card

The output modes of the computer graphics card are divided into copy output and extended output, and can be switched as needed. In copy output mode, when multiple external monitors are connected, they will repeatedly display the current screen; in extended output mode, the external monitor displays an extended screen, which seems to form a larger extended desktop.
The basic configuration of the LED display is usually set to copy output to ensure that the screen display is consistent with the computer desktop. With the help of desktop icons, the integrity of the screen can be easily judged, and the configuration can be completed efficiently.

Regular Operation Steps:
(1) Right – click on the blank area of the computer desktop and select the “Display settings” option (as shown in Figure 4 – 1);
(2) Select “Duplicate these displays” or “Extend these displays” to achieve the corresponding output (the “Display settings” interface is as shown in Figure 4 – 2).

Quick Operation Steps:
(1) Press the “Windows” + “P” keys on the keyboard at the same time;
(2) Select “Duplicate” or “Extend” in the pop – up shortcut menu (the copy setting of the graphics card is as shown in Figure 4 – 3).

Figure 4-1 “Display settings” option

Figure 4-2 “Display settings” interface

Figure 4-3 Graphics card copy setting

1.2 Graphics Card Scaling Settings

Usually, due to the differences in computer screen sizes and graphics card display performance, graphics cards provide different scaling ratios to meet user needs. In the basic configuration of an LED display, the scaling value is generally set to 100% to ensure that the output resolution of the graphics card corresponds to the resolution of the sending card in a point-to-point manner (one pixel in the video source corresponds to one pixel on the LED display), and at this time, the display effect of the LED display is the best.

Operation Steps:

Right-click on the blank area of the computer desktop, and select the “Display settings” option from the pop-up shortcut menu.
In the “Scale and layout” section, select the “100%” option from the drop-down list of “Change the size of text, apps, etc.”, and the option will take effect after exiting, as shown in Figure 4-4.

Figure 4-4 “Scale and layout” section

2. Sending Card Settings

The setting of the sending card takes the basic configuration software NovaLCT of Novastar as an example, and the processes and logics of configuration software from other manufacturers are similar.

2.1 Login to Display Configuration Software

Open the NovaLCT software, select “Login” → “Synchronous advanced login” in turn, enter the login password, and open the main interface of the software. The login interface of NovaLCT software is shown in Figure 4-5.

Figure 4-5 NovaLCT software login interface

2.2 Input Source Information Settings

The purpose of input source information setting is to ensure that point-to-point output is correctly set on the sending card.

The basic information of the input video source mainly includes the input source type (HDMI, DP, DVI, etc.), resolution (standard or custom), refresh rate (24Hz, 30Hz, 50Hz, 60Hz, etc.), and input source bit depth (8bit, 10bit, 12bit). After inputting or selecting the basic information, click the “Set” button to complete the setting of the video source, as shown in step “1” in Figure 4-6.

Figure 4-6 Sending card setting interface

After the setting is completed, click the “Refresh” button in step “2” in Figure 4-6. When the resolution of the sending card is consistent with the output resolution of the graphics card, it can be confirmed as point-to-point output.
Click the “Solidify” button in step “3” in Figure 4-6 to solidify the parameter settings, so that even if the sending card is powered off and on, the set parameters will not be lost.

3. Receiving Card Settings

3.1 Loading of Receiving Card Configuration File

Usually, LED cabinets have corresponding receiving card configuration files when they leave the factory. The files contain information such as module information in the cabinet, driver chips used, decoding chips, scanning methods, resolution, and parameters affecting the display effect of the LED cabinet. It can be understood that the receiving card configuration file is an important file for the normal display of the cabinet. In NovaLCT software, the receiving card configuration file usually has the suffix “RCFGX”.

The operation steps to load the configuration file corresponding to the cabinet into the system are as follows:

Open the receiving card setting interface, and click the “Load from file” button at the bottom of the interface. The loading of the configuration file is shown in Figure 4-7.

Figure 4-7 Loading of configuration file

Select the file location in the pop-up path dialog box, as shown in Figure 4-8. Take the file with the type “RCFGX” and the name “DEMO” as an example, select the file and click the “Open” button. At this time, the configuration file parameters of “DEMO” are loaded into the software. After the loading is completed, a prompt “Loading configuration file successfully!” will appear, and click the “OK” button, as shown in Figure 4-9.

Figure 4-8 Selection of configuration file path

Figure 4-9 Prompt for successful loading of configuration file

After successfully loading the configuration file, the parameters in the “Light board information”, “Cabinet information”, and “Performance settings” of the receiving card interface will become the parameters in the “DEMO” file.

3.2 Sending of Receiving Card Configuration File

After the receiving card configuration file is successfully loaded, the system only obtains the correct configuration parameters, and it is also necessary to send them to the receiving card so that the c

orresponding cabinet can display normally.

The operation steps to send the configuration file to the receiving card are as follows:

Click the “Send to receiving card” button on the receiving card setting interface, and a “Send parameters to receiving card” dialog box will pop up at this time, as shown in Figure 4-10.

Figure 4-10 Sending to receiving card

If all receiving cards connected to the control system have the same loaded cabinet resolution and consistent parameters, select the “All receiving cards” radio button, and then click the “Send” button to broadcast the parameters to all connected receiving cards. If there are cabinets of different specifications, select the “Designated receiving cards” radio button, and then select the designated receiving card position from the topology diagram for sending.
After the receiving cards are correctly set, the screen of the display will be displayed repeatedly in units of receiving cards, and the display range is the size of the area loaded by the receiving card in the upper left corner of the video source. Figure 4-11 shows the display of 8 receiving cards’ loaded areas. It should be emphasized here that in the control system, a single receiving card represents a single cabinet, but in practice, there may be a physical cabinet containing two receiving cards, which should be regarded as two cabinets in the control system.

Figure 4-11 Display of 8 receiving cards’ loaded areas

3.3 Solidification of Receiving Card Configuration File

After the configuration file is sent to the receiving card, all parameters in the file have been successfully applied to the receiving card. However, if you want the parameters not to be lost after the receiving card is powered off and on, you need to perform a “solidification” operation to write the parameters into the Flash memory of the receiving card. Click the “Solidify” button on the receiving card setting interface, and complete the solidification process according to the prompt in the pop-up window. After successful solidification, a dialog box “Successfully saving information to hardware!” will pop up, and click the “OK” button, as shown in Figure 4-12.

Figure 4-12 Solidification of receiving card configuration file

3.4 Reading Back of Receiving Card Configuration File

The operation of reading back the receiving card configuration file is required in the following two cases:

When there is no configuration file on site, the parameters can be read back from the normally displayed cabinet and saved to a file, as shown in Figure 4-13.
When part of the cabinet display is abnormal, the configuration file can be read back from other receiving cards with the same configuration and normal display, and then sent.

After clicking the “Read from receiving card” button, a “Please select receiving card” dialog box will pop up, and you can select the sending card number, output port number, and receiving card number in turn. The reading back of the receiving card configuration file is shown in Figure 4-14. The sending card number, output port number, and receiving card number are 1, 2, and 1 respectively, which means reading the parameters of the first receiving card under the second output network port of the first sending card. Click the “OK” button, and after the reading back is completed, the software will prompt “Successfully reading back information from the receiving card”. At this time, the parameters on the receiving card interface will be refreshed to the parameters after reading back, and sending these parameters to the receiving card with abnormal display can complete the operation.

Figure 4-13 Reading configuration file from receiving card

Figure 4-14 Reading back of receiving card configuration file

4.Receiving Card Settings

In Figure 4-11, after the receiving card is set, each receiving card displays a repeated picture, which is the size of the area loaded by the receiving card in the upper left corner of the video source. This is because each receiving card does not know the specific coordinate position of the image it should display. Therefore, it is necessary to inform each receiving card which part of the video source image they should display through the display connection operation. The specific operation steps are as follows.

4.1 Regular Operation Steps

Open the display connection interface as shown in Figure 4-15, and perform the following operation steps:

The “Number of displays” is 1 by default, click the “Configure” button. “Number of displays” refers to the number of displays in the control system, and there is usually only 1 display in the basic configuration.
Fill in the corresponding numbers in the value boxes after “Number of receiving card columns” and “Number of receiving card rows”. As shown in Figure 4-15, set it to 4 columns and 2 rows of receiving cards. After entering the number of rows and columns of the receiving cards, click the “Reset all” button or press the “Enter” key.
In the “Sending card number” section, you can see the number of sending cards connected under the current control system. Select the sending card number corresponding to the target screen, and similarly, you need to select the network port number corresponding to the output of the sending card.
Set the width and height of the receiving card in the “Receiving card size” section, that is, the size of the area loaded by the receiving card. The relevant parameters can be obtained from the “Cabinet information” section in the receiving card setting interface in Section 3.1.3.

Figure 4-15 Display connection

After completing the above settings, you can start the display connection operation. The sending of display connection parameters is shown in Figure 4-16.

Figure 4-16 Sending of display connection parameters

Complete the display connection by dragging the mouse or using the keyboard direction keys. When connecting the display, you need to observe the network cable connection direction from the front of the screen (front view), then find the correct starting point on the topology diagram, and start the connection.
After drawing the display connection topology diagram, click the “Send to hardware” button.
After sending the screen connection information to the hardware, click the “Solidify” button, and the display connection information will be successfully saved in the hardware.

It should be noted that the display connection information is saved in the sending card, so when replacing the sending card, it is necessary to reset the display connection information. When the display connection is completed, the screen will display a complete picture, which is the area of the display resolution size in the upper left corner of the video source. The completed display connection is shown in Figure 4-17.

Figure 4-17 Completed display connection

4.2 Mapping Function

The application scenarios of the Mapping function mainly include two types:

Scenario 1: When installing and debugging a new screen on the engineering site, the Mapping function can be used to judge the correct network cable connection mode without connecting a video source device, making on-site screen connection more convenient and fast.
Scenario 2: When the display screen is not connected normally and there is disordered and misplaced display, the Mapping function can be used to verify whether the on-site network cable is inserted incorrectly, or whether there is a discrepancy between the software display connection setting and the physical network cable connection.

The operation steps of the Mapping function are as follows:

Open the “Display connection” tab, and click the “Enable Mapping” button at the bottom, as shown in Figure 4-18.

Figure 4-18 Enabling Mapping function

After enabling the Mapping function, each cabinet of the LED display will display the physical connection information of the receiving card. The demonstration of the Mapping function is shown in Figure 4-19. Among them, “S” refers to the sending card, that is, the number of the sending card device under the current communication serial port; “P” refers to Port, that is, the output network port; “# number” indicates the number of the receiving card under the network port. Taking the display shown in Figure 4-19 as an example, the display is loaded through sending card 1, using 1 network port, namely “network port 1”, and there are 8 receiving cards connected. The connection sequence starts from the upper right corner, connects in series to the 4th receiving card to the left, then connects to the receiving cards in the second row, and then completes the network cable connection to the right in turn.

Figure 4-19 Demonstration of Mapping function

Perform the correct display connection operation again according to the Mapping information, as shown in Figure 4-20.

Figure 4-20 Correct display connection

Resend and solidify, and the LED display can realize the complete display of the picture as shown in Figure 4-21.

Figure 4-21 Complete display of the picture

4.3 Coordinate Offset

In some application scenarios, if we want the LED display to only display the picture at a specific position on the video source picture, we can use the coordinate offset function of the display connection interface to achieve this effect.

In the “Basic information” section of the “Display connection” tab, you can set the X and Y coordinate values to achieve coordinate offset. In the example shown in Figure 4-22, both the X and Y values of the connection diagram are set to 200, that is, all are offset by 200 pixels.

Figure 4-22 Coordinate offset setting

After sending the parameter information to the hardware and solidifying it, the actual display picture of the LED display is as shown in Figure 4-23, and the picture will start to be displayed from the coordinate (200, 200) of the desktop.

Figure 4-23 Display picture after coordinate offset

4.4 Screen Space Reservation

In some creative projects, in order to realize the irregular shape of the screen, some hollow installation methods are often used when building the LED display. The hollow design of the screen is shown in Figure 4-24. During the LED display connection operation, there is no actual cabinet connection information in the hollow area, but in order to keep the overall picture unchanged, the position of this area still needs to be reserved, and at this time, the screen space reservation function needs to be used.

Figure 4-24 Hollow design of the screen

Assuming that in the hollow design area of the LED display shown in Figure 4-24, the resolution of a single cabinet is 128×128 pixels, the display connection operation is as follows: in the “Receiving card size” section of the “Display connection” tab, set the width and height parameters, and check the “Reserve position” checkbox to realize the hollow effect of the display. The screen space reservation setting is shown in Figure 4-25, and the position of the cabinet in the 2nd row and 2nd column is set to “Reserve position”.

Figure 4-25 Screen space reservation setting

4.5 Rectangular Loading Principle

In the screen settings of NovaLCT software, to improve the efficiency of data packet transmission between the sending card and receiving card of the control system and ensure a more stable display of the LED screen, many control system manufacturers have designed the “rectangular loading” principle in the display connection operation. That is, during data processing, the control system packages the video source image according to a rectangular range and provides it to the backend receiving card. Each receiving card obtains its own part from the rectangular data packet according to the position of the screen it carries. This design principle has a drawback: it causes waste of network port bandwidth resources.

For example, there is a special-shaped screen as shown in Figure 4-26. Although the network cable is actually connected to 7 cabinets, since it is built based on a “3×3 rectangle” canvas, the control system calculates the loading resources according to 9 cabinets. The “rectangular loading” principle improves system stability to a certain extent but also causes waste of some network port resources, which needs to be fully considered in the early design scheme; otherwise, the scheme may fail.

With the development of technology and the optimization of the underlying algorithm logic of the control system, the utilization of network port bandwidth has become more sufficient and efficient. At present, some control system manufacturers calculate the loading based on the actual number of connected cabinets, breaking away from the restriction of the “rectangular loading” principle, which is an inevitable trend in the development of control systems.

Figure 4-26 “Rectangular loading” rule

System Backup Settings

Redundant backup settings are a very important function in rental and fixed installation businesses. LED displays often encounter network cable disconnection during use. To ensure that the LED display can still display normally when the network cable is disconnected, Novastar has developed a redundant backup function. There are three ways to implement the redundant backup function: backup between different network ports of the same sending card, backup between cascaded sending cards, and backup between non-cascaded sending cards.

Assume that in a project, an LED display is carried by two output network ports of one sending card, and the other two output network ports are used for backup. Based on this, the setting methods of the three different backup modes are introduced below.

1. Sending Card Cascading Backup

When the resolution of the LED display exceeds the carrying capacity of a single sending card, multiple sending cards are usually cascaded to control the LED display. At this time, it is necessary to cascade multiple sending cards so that all sending cards are in the same control system to achieve unified control and adjustment.

Currently, there are many ways to cascade sending cards in LED control systems, which are mainly related to the design of the device’s cascading interface.

1.1 Cascading with 5Pin Cascade Cable

If early bare-card control cards are used, to cascade multiple control cards, first find the cascading interface on the control card. Taking Novastar’s MSD300 control card as an example, its interface J18 is the cascade output port, and interface J6 is the cascade input port. Then use a special 5Pin cascade cable to connect J18 and J6 to complete the cascading of two control cards.

Figure 4-27 Cascading with 5Pin cascade cable

1.2 Cascading with Aviation Plug Cascade Cable

In the evolution from bare-card control cards to chassis-type controllers, the cascading port has also changed to an aviation plug 5Pin cascade cable. This interface uses a buckle design to make the connection more stable. Taking Novastar’s MCTRL300 as an example, it actually leads the cascading signal of the bare card to the chassis. Therefore, during cascading, an aviation plug cascade cable is needed to connect the UART OUT interface of the first sending card to the UART IN interface of the second sending card to complete the cascading operation.

Figure 4-28 Cascading with aviation plug cascade cable

1.3 Cascading with Network Cable

The cascading method using 5Pin wires has certain drawbacks in engineering sites. Therefore, in Novastar’s upgraded product MCTRL660, the cascading interface is designed as a network port.

Figure 4-29 Cascading with network cable

As the most commonly used wire in engineering sites, network cables make device cascading easy. Simply use a network cable to connect the UART OUT interface of the first sending card to the UART IN interface of the second sending card to complete the cascading operation.

1.4 Cascading with USB Cable

Although network cable cascading is more convenient, it has a drawback: the crystal head of the network cable is easily damaged, leading to loose cascade cables, poor contact, or unstable cascade signals. The USB interface is relatively more stable. Therefore, in newly developed sending card devices, most control system manufacturers have tacitly used the USB interface as the cascading interface between devices.

Figure 4-30 Cascading with USB cable

It should be noted that only sending cards of the same model can be cascaded, and sending cards of different models cannot be cascaded. After the sending cards are cascaded, you can click “View Device Details” on the main interface of NovaLCT software, and check whether the cascading is successful in the pop-up “Total Number of Device Types” window.

Figure 4-31 Checking cascading success

When multiple devices appear under the same communication port, it indicates that the cascading is successful.

2. Backup Settings Between Different Network Ports of the Same Sending Card

2.1 System Architecture

Taking Novastar’s video controller VX4S as an example to introduce its system architecture.

Figure 4-32 System architecture of backup between different network ports of the same sending card

As shown in Figure 4-32, the screen is carried by network port 1 of the sending card, and network port 2 is used as the backup of network port 1. Therefore, in hardware connection, a network cable is needed to connect network port 2 of the sending card to the last network port of the last receiving card of the display to form a closed loop in the entire system.

2.2 Software Settings

After the hardware connection is completed, perform software settings as follows:

(1) Log in and open the main interface of NovaLCT software. You can see that the number of control systems is 1. Click the “View Device Details” hyperlink. In the pop-up “Total Number of Device Types: 1” dialog box, you can see that the “Number of Devices” is 1, that is, the number of sending cards is 1.

Figure 4-33 Checking the number of control systems and sending cards

(2) According to the actual wiring method, connect the screen in NovaLCT software to make the screen display normally.

Figure 4-34 Performing screen connection

If the screen connection is incorrect, the backup setting cannot work normally.

(3) Enter the “Sending Card” tab interface to set redundant backup.

Figure 4-35 Redundant backup setting

① In the “Sending Card” tab interface, click the “Add” button below to open the “Redundant Setting” dialog box.
② Add redundant backup information: Set “Master Output Port Number” to 1 and “Backup Output Port Number” to 2, indicating that network port 2 is the backup of network port 1.
③ Click the “Add” button to confirm that all network port settings are correct.
④ Click the “Send” button to send all settings to the hardware, i.e., the sending card.
⑤ Click the “Solidify” button to solidify the redundant backup information into the sending card, and the redundant backup setting is completed.

3. Backup Settings Between Cascaded Sending Cards

3.1 System Architecture

Still taking Novastar’s video controller VX4S as an example, the sending cards are cascaded via USB cables. The front-end video source computer provides two identical video source signals through a video processor and distributes them to two sending cards. The first sending card uses network ports 1 and 2 to carry the screen, and the second sending card uses network ports 1 and 2 for backup, forming a closed loop.

Figure 4-36 System architecture of backup between cascaded sending cards

3.2 Software Settings

(1) Log in and open the main interface of NovaLCT software. The main interface shows that the number of control systems is 1. Open the “Total Number of Device Types: 1” dialog box, and you can see that the “Number of Devices” is 2, that is, the number of sending cards is 2, indicating that the two sending cards are cascaded.

Figure 4-37 Single system + two sending cardsFigure 4-37 Single system + two sending cards

(2) According to the actual wiring method, use sending card 1 to connect the screen in NovaLCT software to make the screen display normally.

Figure 4-38 Using sending card 1 for screen connection

If the screen connection is incorrect, the backup setting cannot work normally.

(3) Enter the “Sending Card” tab interface to set backup.

Figure 4-39 “Sending Card” tab interface

① In the “Sending Card” tab interface, click the “Add” button below to open the “Redundant Setting” dialog box.
② Add the redundant backup sequence: Set “Master Sending Card Number” to 1, “Backup Sending Card Number” to 2, “Master Output Port Number” to 2, and “Backup Output Port Number” to 2, indicating that network port 1 of the second sending card is the backup of network port 1 of the first sending card.
③ Click the “Add” button to confirm that all network port settings are correct. If there are more network port correspondences, they can be added in the same way.
④ Click the “Send” button to send all backup settings to the hardware.
⑤ Finally, click the “Solidify” button to solidify the redundant backup information into the sending card, and the backup setting is completed.

4. Backup Settings Between Non-Cascaded Sending Cards

4.1 System Architecture

The system architecture of backup between non-cascaded sending cards is roughly the same as that of cascaded sending cards. The main difference is that in the non-cascaded case, the two sending cards are connected to the upper computer control computer via USB cables respectively, that is, there are two independent control systems in the current architecture.

Figure 4-40 System architecture of backup between non-cascaded sending cards

4.2 Software Settings

(1) Log in and open the main interface of NovaLCT software. You can see that the number of control systems is 2. In the “Total Number of Device Types: 2” dialog box, it shows that there are two independent communication ports in the system, that is, there are two control systems and two sending cards.

Figure 4-41 Two control systems + two sending cards

(2) When clicking the “Display Configuration” button on the main interface of NovaLCT software, a dialog box will pop up.

Figure 4-42 Master device setting

In this example, select the communication port “USB@Port_#0002.Hub_#0002” as the master device. According to the actual wiring method of the display, connect the display in NovaLCT software to make the screen display normally.

Figure 4-43 Setting the display connection of the master device

(3) Open the “Sending Card” tab interface for backup settings. In this setting, there is no need to add the corresponding relationship of backup. Just check the “Set as Master” checkbox in the “Redundancy” section at the bottom of the interface, and then solidify all settings.

Figure 4-44 Master device setting

(4) Return to the display configuration page and select another communication port for configuration, i.e., the “USB@Port_#0003.Hub_#0002” communication port. The sending card under this communication port is the backup device. At this time, it is necessary to perform the same display connection operation as the master device.

Figure 4-45 Setting the display connection of the backup device

(5) Enter the “Sending Card” tab interface again for backup settings. At this time, just check the “Set as Backup” checkbox, and then solidify all settings.

Figure 4-46 Backup device setting

4.3 Hardware Setting Backup

For the backup setting of non-cascaded sending cards, after completing the display connection using hardware, redundant backup settings can also be directly performed through the front panel of the sending card. Still taking Novastar’s VX4S as an example to introduce the specific operation.

Figure 4-47 Hardware setting backup

On the front panels of the two sending cards, select “Advanced Settings” → “Redundant Settings” → “Set as Master”/”Set as Backup” in sequence. The operation logic of the front panel of different models of sending cards is roughly the same. For specific operations, please refer to the user manual of the sending card of that model.

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