Overview of Interface Options

Overview of Interface Options

Apr 11th 2023

Understanding how to configure your LCD may seem difficult, but the design is often clear, depending on your use case. For TFT displays, various interfaces are possible, but choosing the right one will determine if your LCDs meet your needs.

TFT displays are currently found in various items, including TVs, laptops, appliances, instruments, mobile devices, etc. Adding thin film transistors to LCD architecture dramatically increased LCD use across all market categories. Each transistor in the liquid crystal display's (LCD) thin-film transistor (TFT) technology serves as a pixel (that is, for each of the tiny elements that control the illumination of your display). Since every pixel has a transistor, the current required to turn on and off the pixel lighting can be minimized. There are two common types of interfaces on TFT displays, LVDS and TTL.

LVDS is a method for transmitting display data that uses differential signaling at low voltages. Versatile screens, high-definition visuals, and quick frame rates are all advantages of these interfaces because fewer connections are needed to interact with the display.

The TTL interface is a versatile, low-cost, and widely compatible one that is best regarded for its reliability and availability. A TTL chip contains many transistors which serve the purposes of logic and amplification, a simple yet ingenious design. The key advantage of TTL is that it is simple to link with other circuits and can provide complex logic functions due to particular voltage levels and good noise margins.

Another option for display communication is MIPI DSI or CSI. Smartphones, tablets, smartwatches, and other embedded display applications use the high-speed MIPI DSI interface. The Display Serial Interface, or DSI, is a serial communication protocol created by the Mobile Industry Processor Interface Alliance (MIPI). Low EMI, excellent performance, and low power data transfer are all features of MIPI DSI. Additionally, the interface standard reduces the number of pins to lessen design complexity while retaining vendor compatibility. High-level graphics benefit MIPI DSI displays, which feature less complicated signal routing, PCB designs, and higher hardware costs. MIPI CSI is a widely adopted, high-speed protocol for transmitting still and video images from image sensors to application processors, whereas DSI is a high-speed interface that is scalable and forward-looking and defines the high-bandwidth connection between host CPUs and displays.

Another option for designing an LCD could be MCU or RGB for the interface. When selecting an MCU, many considerations need to be taken into account. You should take the application's complexity into account. Larger program memory is frequently necessary for complicated devices. Make a list of the peripherals and communication requirements for the device in addition to that. In some applications, it may also be necessary to use internal features such as the power management module and bootloader. The choice of an MCU might occasionally be influenced by the development tools. You should choose one with user-friendly programming tools and IDEs (Integrated Development Environments). Unlike the MCU interface, the RGB interface operates without any involvement from a frame buffer. The number of data pins used for each of the RGB signals might range from 16 to 18 or 24. Deciding whether to use the MCU or RGB interface depends primarily on how the display will be used. The CPU and memory requirements depend on the interface being used. Other aspects like pin availability and processing speed must be considered when selecting an interface. High-performance programs can employ RGB, but doing so necessitates more pins, faster processing, and more memory. Given that it has an internal frame buffer and the ability to store memory, a parallel MCU can be an excellent choice for showing graphics. Due to less stringent timing requirements than RGB, the MCU interface is generally easier to use.

Finally, Thin Film Transistors (TFTs) are less widespread than other types of displays and components regarding serial peripheral interfaces (SPI) for various reasons. One of the main causes is that SPI is a form of communication protocol intended to communicate with peripheral devices, such as sensors, memory, and other microcontrollers, but TFTs are built particularly for display applications. This is why TFTs are not commonly used with SPIs.

No matter what type of interface you choose for your TFT displays, FocusLCDs is here to help you make the right choice for meeting your display needs for your unique use case.