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LCD-TFT displays are now widely used in industrial devices. Designers typically focus on optical parameters such as resolution, brightness, and contrast. In practice, however, image quality depends not only on the panel itself, but also on how it is controlled. The control architecture and the communication interface used determine, among other things, the refresh method, color reproduction, brightness stability, and the smoothness of user interface animations. An improperly selected controller or incorrect signal configuration can lead to image artifacts, reduced effective brightness, degraded contrast, or unstable display operation.
Issues related to LCD-TFT display control are a key aspect of electronic device design. In this article, we present the main elements of display control architecture and the factors that should be considered already at the system design stage.
What is LCD-TFT Display Control?
The term “LCD-TFT display control” refers to all mechanisms, signals, and procedures responsible for transmitting image data and managing the operation of the panel. This includes, among other things, pixel data transmission, generation and synchronization of timing signals, configuration of display operating parameters, as well as control of the backlight system.
The TFT panel itself is not an autonomous component – it requires appropriate control electronics to function properly, providing data and managing its operation. Depending on the system architecture, this role may be performed by a dedicated display controller. In many solutions, this function is also integrated into a microcontroller or application processor, which generates control signals and transmits image data directly to the panel.
Proper display control has a direct impact on image stability, color reproduction, user interface smoothness, and overall system reliability. For this reason, correctly addressing the display communication method and control architecture is one of the key aspects of designing devices equipped with LCD-TFT displays.
What is required to control a TFT display?
A typical LCD-TFT display control system consists of several basic elements:
- a signal source, such as a microcontroller or SoC system,
- a communication interface through which image data is transmitted,
- a display controller responsible for mapping data to pixels,
- an LED backlight system along with its control circuitry,
- a suitable power supply ensuring stable operation of the entire module.
The correct operation of all these elements determines the stability of the display and the quality of the generated image.
Most common communication interfaces used in LCD-TFT displays
Depending on the type of display, its resolution, and application requirements, different communication interfaces are used to transmit image data between the controller and the LCD-TFT panel. They differ in, among other things, the method of data transmission, the number of signal lines, bandwidth, and the complexity of implementation.
RGB
The RGB interface is one of the simplest and most commonly used methods of controlling TFT displays. Image data is transmitted in parallel – each color component (R, G, B) is carried over separate lines, typically in 16-, 18-, or 24-bit format.
In addition to data lines, synchronization signals such as HSYNC, VSYNC, DE (Data Enable), and the pixel clock (PCLK) are also used. The RGB interface enables direct and continuous transmission of pixel data, ensuring smooth image display, but it requires a relatively large number of signal lines and precise timing synchronization.
LVDS
The LVDS (Low Voltage Differential Signaling) interface is a high-speed communication standard used in displays with larger sizes or higher resolutions. Data is transmitted as differential signals, which reduces susceptibility to electromagnetic interference and enables stable transmission over longer distances.
Thanks to data serialization, the number of required wires is lower than in parallel interfaces, while maintaining high bandwidth. This solution is commonly used in displays designed for industrial applications.
MIPI DSI
The MIPI DSI (Mobile Industry Processor Interface – Display Serial Interface) is a modern communication standard used in LCD-TFT displays. It utilizes high-speed differential transmission lines, which reduces the number of required connections and simplifies electronic system design.
Thanks to its high bandwidth, MIPI DSI enables support for high-resolution displays while maintaining a low number of signal lines. This makes it particularly suitable for compact devices and modules, where minimizing connections and saving space is essential.
SPI
The SPI interface is mainly used in small displays with relatively low resolution. Its main advantages are simple implementation and a low number of required signal lines.
In such solutions, image data is transmitted serially to a controller located within the display module, which manages the GRAM (Graphics RAM) storing the current screen content. Due to its limited bandwidth, SPI is primarily used in simpler applications and user interfaces with low dynamic content changes.
QSPI
QSPI is an extension of the SPI interface that enables parallel data transmission over multiple lines simultaneously. This significantly increases bandwidth compared to standard SPI, while maintaining relatively simple implementation.
In practice, QSPI is used, among other things, for communication between a microcontroller and external graphics controllers, such as EVE-type devices. The higher bandwidth allows faster transmission of data and commands related to user interface handling, which is particularly important in more demanding graphical applications.
As a result, QSPI is used in systems that require support for higher-resolution displays while still maintaining a limited number of signal lines.
MCU interfaces (8080 / 6800)
MCU interfaces, also known as 8080 or 6800 modes, resemble communication with parallel memory. The microcontroller writes data directly to the registers or display memory of the display controller.
This solution is used in displays equipped with an integrated graphics controller, which manages image refreshing and generates control signals for the TFT panel. As a result, the requirements placed on the microcontroller are lower, although this comes at the cost of reduced data transmission performance.
Selecting the appropriate interface has a direct impact on system performance, image smoothness, the number of required signal lines, and the overall complexity of the electronic design.
Learn more about interfaces in our blog guides:
Overview of popular interfaces for image transmission – part 1,
Overview of popular interfaces for image transmission – part 2.
Display controller
In the architecture of systems using LCD-TFT displays, the display controller is one of the key components responsible for proper panel control and image presentation. Every LCD-TFT display includes an internal controller that performs the basic functions required for its operation, such as signal synchronization, pixel addressing, and adapting control signals to the requirements of a specific panel. Without this element, correct display operation would not be possible.
However, it should be emphasized that the presence of an internal controller does not mean that the display fully handles the graphics layer. Functions related to user interface generation may be performed by an additional image controller or directly by a microcontroller or SoC. In practice, it is also necessary to generate image data, manage memory, and handle graphical elements such as text, icons, or animations. The way these functions are implemented depends on the system architecture and directly affects project complexity, hardware requirements, and the capabilities of the final device.
Regardless of the chosen architecture, the internal display controller is always a common element, while the differences lie in how image data is generated and processed on the host system side.
TFT display control using an external image controller
In this approach, the internal display controller works together with an additional external image controller responsible for graphics generation and user interface handling. The microcontroller does not control the display directly but communicates with the graphics controller, which then sends the appropriate data to the TFT module.
The external image controller takes over tasks such as graphics rendering, animation handling, image memory management, and interpretation of graphical commands. As a result, the main microcontroller is not burdened with real-time image generation. This reduces requirements for processing power and memory resources within the system.
Controllers from the EVE (Embedded Video Engine) family are one example of specialized graphics controllers. They typically communicate with the microcontroller via SPI or QSPI, and with the TFT display through a parallel RGB or LVDS interface. Instead of transmitting full image data, the microcontroller sends commands related to user interface generation, such as displaying text, drawing graphical elements, or handling predefined widgets. The controller itself is responsible for image generation, graphics layer management, and – depending on the version – features such as touch functionality. This approach significantly reduces microcontroller load and simplifies HMI implementation.
TFT display control using a microcontroller or SoC
In this approach, the TFT display is controlled directly by a microcontroller or SoC with an integrated image controller. The LCD-TFT module itself still includes an internal controller required for proper panel operation, but the generation and transmission of image data are handled by the host system. As a result, there is no need for an additional external graphics controller, since image creation and processing functions are implemented on the control unit side.
This solution provides greater design flexibility and full control over how content is generated and presented. It enables precise management of the frame buffer, rendering methods, and user interface structure, allowing the system to be tailored to specific application requirements.
This approach is typical for more advanced systems that use high-performance microcontrollers or SoC platforms with sufficient processing power, communication interfaces, and memory resources required for graphics handling. It is commonly used in devices that require higher resolution, greater image dynamics, and more complex user interfaces. However, it should be noted that this solution comes with increased design complexity and higher hardware requirements. It requires proper system resource management, correct interface configuration, and consideration of image processing performance already at the design stage.
In practice, the choice of architecture depends primarily on application requirements, the expected level of interface complexity, available hardware resources, and project priorities. In cases where simplicity of implementation, reduced microcontroller load, and easier integration are key, using an external image controller is a favorable solution. On the other hand, in projects requiring higher performance, more advanced graphics, and the use of modern computing platforms, it is justified to use a microcontroller or SoC with an integrated image controller.
In both cases, the LCD-TFT display relies on its internal controller, which is responsible for basic panel control and remains an essential element for proper operation of the entire system.
Configuration of LCD-TFT displays
After power-up, an LCD-TFT display requires proper configuration of its operating parameters. This process involves setting the correct parameters of the display controller and the communication interface to enable proper transmission and display of image data. The configuration method depends on the specific display model and the controller used, and is typically described in the manufacturer’s documentation.
During configuration, the following parameters are typically set:
- image orientation,
- color format and depth,
- refresh rate and signal timings,
- communication interface mode,
- backlight control parameters.
In many displays, configuration is performed by sending an appropriate sequence of initialization commands to the display controller. As a result, the required values are written into the controller’s configuration registers, enabling correct panel operation. Only after this stage is completed can the image be displayed properly.
LCD-TFT backlight control
LED backlighting is one of the key elements affecting the readability of LCD-TFT displays. Since the liquid crystal matrix itself does not emit light, image visibility is made possible by a backlight system placed behind the display or along its edges.
Modern solutions use LEDs driven by dedicated driver circuits, which ensure stable operating current and enable precise brightness control. In practice, this control is most often implemented using PWM modulation, where the PWM signal drives the LED driver input, and the driver is responsible for proper current regulation of the LEDs. This approach allows smooth brightness adjustment without degrading image quality.
In many applications, backlight brightness is additionally adjusted automatically to ambient conditions based on measurements from light sensors.
A properly designed backlight control system has a significant impact on both user interface readability and the overall energy efficiency of the device.
Common issues in TFT display control
When designing systems using LCD-TFT displays, various issues may arise related to the integration of the panel with the control system. The most common include:
- no image after device startup,
- flickering or unstable display,
- incorrect color reproduction,
- image noise or artifacts,
- insufficient readability in bright environments.
In many cases, these problems result from an incorrect selection of the communication interface, improper configuration of the display controller, or inadequate backlight control. They may also be caused by incorrect signal timing parameters, such as the pixel clock.
Some of these issues can be resolved at the software configuration stage or by adjusting display controller parameters. However, hardware-level design errors – such as an unsuitable interface architecture or improper signal matching – often require changes to the electronic design.
Unisystem support in projects
Unisystem provides support at every stage of designing systems with LCD-TFT displays.
Our Solution team delivers projects that cover not only the display itself, but also all elements required for its integration into the target device. This includes, among other things, integration of electronic and mechanical components, touch controller calibration, selection of appropriate bonding materials, and customization of cover glass. As a result, a complete and cohesive display module is created – for example, based on LCD-TFT technology – tailored to operating conditions, environmental requirements, and the specifics of a given application.
The project process begins with an analysis of customer requirements and the development of a solution concept. Then, a team of engineers – including specialists in electronics, mechanics, and software – prepares the design, prototype, and performs system testing and validation. If the prototyping and testing phase is successful, the next step is preparing the solution for mass production.
This approach reduces device development time and minimizes the risk of integration issues. The customer receives not just a single component, but a complete technological solution ready for use in the final product.
LCD-TFT display control is much more than just transmitting an image. It is a complex process that affects content quality, device reliability, and user experience. A properly designed control system allows full utilization of the display’s capabilities and helps avoid issues at the product implementation stage.
The Unisystem team supports customers in designing and integrating LCD-TFT display solutions – from concept to a ready-to-use module. Contact us to discuss your project.
