Blog  /  LCD interface: The ultimate guide

LCD interface: The ultimate guide

Have you ever asked yourself what LCD is? No worries, we are here for you. Therefore, like in any display gadget, liquid crystal display coordinates with a microprocessor or microcontroller. The MCPU and MCU send the brightness that every pixel should produce. It creates the required color of the pixel for your LCD screen.

However, the mode of communication between the MPU/MCU and an LCD segment is known as the interface. We shall discuss more of the LCD interface in this guide.

 

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What is an LCD Interface?

 

The LCD interface is a link between the flat panel display module and the multimedia processor. Therefore, the interface can be separated or incorporated as part of the structure on the chip. Additionally, the application produces an image, and then the screen displays it using an LCD interface for the user.

 

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LCD Interface Types

 

LCD interface types

 

There are several Liquid Crystal Display interface types. Below is a highlight of some of the types.

 

Serial Peripheral Interface (SPI)

 

Serial Peripheral Interface (SPI)

 

The Serial Peripheral Interface is a data bus with several lines for the data. It accurately harmonizes the two ends of the data transmission. Therefore, the signal clock rotates, indicating when to sample the data bits on the line.

For instance, every time a change occurs at the visual, it is known as an edge. Therefore, the change can be a rise in voltage or fall in the same.

Besides,  the serial peripheral interface has another component known as the slave select (SS) or chip select. The function of the SS is to wake the peripheral to receive or send data. For instance, since the SPI can support several peripherals, the SS can wake particular peripherals instead of all. Finally, you can use the SPI in graphic, character, digit, and small TFT LCDs. It allows simple interfacing, affordable hardware, and faster speeds than in the SCI.

 

Inter-Integrated Circuit Interface (I²C)

 

Inter-Integrated Circuit Interface (I²C)

 

It is another serial interface in LCDs that resembles the SPI with slave, clock functions, and master. The I²C does not integrate the SS line as in SPI. Therefore, a process known as addressing is essential in selecting a slave to communicate. A frame of the signal is sent on the data bus to address a specific slave after the first bit. Nevertheless, the output signal gets to every slave connected with, although only the slave with the corresponding address to the signal will receive the message.

Additionally, there is a read or write a bit on the address frame indicating when the master should send or receive data from the slave.

MCU Parallel Interface

 

MCU Parallel Interface

 

The MCU interface is essential because it can write and read data stored in the internal frame bugger or the gadget's storage. Therefore, if you want to store images for future use, MCU is the best match for you.

Additionally, in MCU parallel interface for Liquid Crystal Displays, data signals are sent through data lanes on either 18-bit, 16-bit, 9-bit, or 8-bit data channels. Besides, the MCU interface is simple, although it requires a display RAM for its memory functionality. Also, you can use it in graphic LCDs, character LCDs, and small TFT LCDs.

 

LCD Interface for the Large LCD Display.

 

LVDS interface

 

LVDS interface

 

LVDS is an acronym for Low-Voltage Differential Signaling. This type of interface is essential as a complement for large LCDs and peripherals that require high bandwidth, such as HD graphics and fast frame rates. Therefore, it is a good choice due to its fast data transmission while consuming low voltage. One of the LVDS interface wires carries the precise inverse of its companion. Additionally, the electric charge from one wire is correctly masked by the other wire, reducing the interference to the wireless system nearby. Finally, at the recipient end, a circuit checks the variation in voltage between the two wires.

 

Pros

  • Supports smaller voltage swing
  • Has noise blocking ability
  • Has low electromagnetic interference emissions compared to other interfaces
  • Its output does not require external biasing
  • It supports clock, data, and control signals
  • Works best for large displays

Cons

  • It is expensive
  • Works with twisted cable only
  • Has reduced jitter performance

 

RGB interface

 

Red Green and Blue (RGB) interface functions are to link with color displays. It transmits 8 bits of data for each of the colors in every clock oscillation. Therefore, this means there are 24 bits of data sent for every clock oscillation.

Pros

  • Pocket friendly due to technology improvement
  • Offers optimum performance
  • Has high bandwidth capabilities
  • Works well with large displays

Cons

  • Requires expensive connectors and large pin real-estate
  • It causes electrical noise that affects wireless systems

 

EDP interface

 

Currently, you must have seen an improvement in terms of performance as electronic devices become smaller and easy to use. Therefore, this has led to the introduction of an embedded display port. The interface connects a video device to a display device and carries USB, audio, and other data forms. Moreover, this display port offers a high-performance external A/V interface hence high display resolutions of 4K. Additionally, the motive behind the development of this interface is due to several computing requirements. First of all, the main requirement is hardware integration.

Pros

  • Has low EMI hence reducing the need for bulky covering
  • Provides higher resolution, frame rate, and color depth
  • Needs few connections in comparison with LVDS interfaces
  • They are smaller than similar cable types

Cons

  • It is expensive

 

Mobile Industry Processor Interface -MIPI interface

 

MIPI interfaceV

 

This is a new technology development from the MIPI alliance. Mobile Industry Processor Interface has become a preferred option for mobile developers. This interface uses the same signaling as in LVDS. It uses a clock pair and 1-8 data lanes. Mobile Industry Processor Interface supports complex rules that allow low power and high-speed modes. Additionally, it reads data coming from the display at low rates.

 

Pros

  • Works with multiple camera displays
  • Has error correction ability
  • Supports different pixel streams
  • Uses low power
  • Requires low cost for implementation

Cons

  • It is complex
  • Works mainly on cell phone size screens
  • Requires a special board for high-speed transmission

 

Comparison Between  All The Interfaces

 

The table below shows a comparison between the above types of LCD interfaces.

Technology number of Pins Maximum Bandwidth Applications Clock
SPI 6 15MB/sec Small displays on MCU’s 9bits/10 clocks
I2C 5 450KB/sec or 2MB/sec Small displays on PC’s and PC peripherals N/A
RGB 30 for 8 bits/color 24 bits X 50MHz = 1.5Gb/Sec Larger displays 50MHz
LVDS 4, 6, or 8 pairs; 8, 12, or 16 + Clock Pair + grounds +3 = 25 8 x 300MHz x 2 = 2.4 GB/sec; Up to 3.4GB/sec Larger displays, harsh environments 300MHz
MIPI 4 or 8 pairs +clock pair, 10 or 18 4 x 2 GB/sec = 8GB/sec Cell phones N/A

 

 

 Conclusion

 

When choosing the correct display interface for your device, you need to consider several factors. Therefore, it requires you to know how to connect the display to your electronic system. Nevertheless, it would be best if you choose the correct interface for your display. Additionally, consider the amount of data transferred and the refresh rate your system requires.

Finally, we have made it easier as we have given you all the details on each display interface, including the pros and cons. Therefore, having gone through our guide, you will never have issues when making your choice.

 

 

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