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What is an LCD Interface?
LCD screens and modules are effectively useless on their own. After all, you use LCD screens to display visual output from a device. The LCD interface acts as the bridge that connects the LCD to the multimedia device. As you may expect, there are different types of LCD interfaces or rather different ways to interface LCDs with multimedia devices. Nevertheless, LCD modules come with two types of internal interfaces:
- Image Transfer Interface: Can send images
- Universal Interface: Can send other types of data
While Universal Transfer interfaces have their strengths, they aren’t ideal for sending images. Images, especially high-resolution ones, require substantially more bandwidth than most universal interfaces handle. Therefore, they (universal interfaces) are not ideal for live streaming.
Types of Internal Image Transfer Interfaces
Unlike universal transfer interfaces, internal image transfer interfaces enable high-speed transmissions of visual data. Thus, they are ideal for live streams. Of course, different types of internal image transfer interfaces perform differently.
Low Voltage Differential Signal Interface (LVDS)
LVDS cable for mini-ITX motherboard against a black background
The low voltage differential signal interface will be the first example of an image transfer interface. As it’s one of the most common interfaces in industrial applications. Its use of differential signaling is what makes it so popular. This feature lowers the risk of signal interference, and image transmissions tend to be fast.
Furthermore, LVDS interfaces operate at low power and do not depend on specific power supplies or voltages to be effective. You can use it with various low voltage types, such as +3.3v, +2.5v, etc., without disturbing the interface’s performance. Lastly, the LVDS interface is a serial interface.
Red Green Blue (RGB) Interface
The RGB interface receives its name from the RGB color model. It’s one of the oldest transfer interfaces. As such, it’s a parallel interface. This means that it sends every bit on a separate line. This interface would be fast if it weren’t for noise or interference. However, because it doesn’t use differential signaling, it’s highly susceptible to noise, which can often slow the signal down.
Unfortunately, this also means that it is compatible with limited screen sizes. 12-inch screens are the largest screens that LCD RGB interfaces can support. Even so, the RGB interface will only be able to support low resolutions, the highest being 800×600.
Mobile Industry Processor Interface (MIPI)
The mobile industry processor interface has risen in popularity over the last few years. Mobile devices and the Internet of Things(IoT) have become widespread. Consequently, we have seen a rise in this type of image interface.
MIPIs feature low power consumption, fast transfer speeds, and low electromagnetic interference (EMI) because they use differential signaling. Again, the MIP interface is ideal for mobile developers and manufacturers. As such, you will often find them in applications such as:
- Smartwatches
- Mobile video game devices
- Virtual Reality (VR) glasses
- Augmented Reality (AR) glasses
- Embedded Displays
- Smart alarms and meters
- Mobile phones and tablets
Vx1 Image Transfer Interfaces
Similarly to modern image interfaces, the Vx1 image transfer interface uses differential signaling. However, we typically use the Vx1 for sizable high-resolution screens, such as 65-inch 4k television sets. Additionally, you can also use Vx1 image transfer interfaces in applications like:
- Robotics
- Document processing
- Industrial Cameras
- Machine Vision
Embedded DisplayPort (eDP) Image Transfer Interface
Embedded DisplayPort connector for laptop LCD screen
Many view the embedded DisplayPort (eDP) image transfer LCD interface as the successor to the LVDS interface. This is because many applications that use LVDS interfaces now use eDP. Many thin film transistor (TFT) LCD panels now use eDP interfaces.
Nevertheless, its ability to maximize system power efficiency through seamless refresh rate switching is one of its biggest advantages over previous standards and generations.
The IP interface has a small connector and can support 8K resolutions. Because it accommodates faster transfer rates, the eDP LCD interface can facilitate improved color depth and frame rates.
Types Universal Interfaces
We typically use universal interfaces to relay information between microcontrollers and small peripheral devices. Again, many of the LCD interfaces in this section are inappropriate for high-speed video streaming. Instead, they may be ideal for clock displays and calculators.
Serial Peripheral Interface
TFT LCD serial SPI color display module
If you’ve worked on a few DIY electronic projects, you’ve likely come across peripherals using this universal standard. SPIs are fast. They can have baud rates of up to 10MBd or 50 MBd if you use the Quad SPI interface. It’s universal because you can connect it to many inputs and outputs. SPI display interfaces can accommodate TFT screens with sizes of up to 3.5 inches and resolutions of 320×240.
Integrated Circuit (I2C) Interface
16×2 Arduino display or blue LCD with adjustable backlight and i2c wire connection
I2C interfaces aren’t as comparatively as fast as the SPI. Consequently, we traditionally don’t use I2C interface displays for image outputs. Instead, we use them for inputs such as small integrated touchscreen displays.
RS232 Interface
The RS232 is an old interface used primarily as a communication bus. It has a maximum transfer speed of 19 kbps. The RS232 is near obsoletion as Universal Serial Buses (USBs) have replaced them.
Universal Asynchronous Receiver-Transmitter (UART) Interface
You can typically find the UART interface in simple LCD modules. While it performs similarly to the RS232 interface, it’s an exclusively internal interface. Again, it is not appropriate for LCDs, especially high-resolution ones. Nevertheless, we can overcome some of its shortcomings by using an intelligent display that converts or generates images from commands we send through the UART interface.
Conclusion
The above guide explores what LCD Display interfaces are. Additionally, it explores all the various types of interfaces available to you. If you’re planning to create an LCD-based project, you can use this guide to determine which LCD interface is suitable. However, peripherals are only a single part of an electronics project. You’ll most likely require a PCB. Contact WellPCB for all your PCB fabrication and assembly needs. We’re always happy to help.
