Displays play a crucial role in embedded applications. There are several kinds of displays manufactured by various vendors in the market. The type of display to be used depends on the application need. Here are some of the displays commonly used in the market.
Seven Segment Display:
This is one of the simplest display used in the embedded applications. Mostly used by hobbyists and some of the industrial applications. The display has 7 segments and can display numbers from 0 to 9. Below image shows how the segment display looks like:
Seven Segment display is available in two different configurations. One is common anode and the other one is common cathode. The below implementation is an example of common anode where all the anode of the LEDs are connected together.
Within the seven segment there is something called multi digit display where there shall be option for more than one 7-segment included. These are commonly used for counters and for clocks in public places. Below is the 3-digit segment display
Below is how the clock with multi digit display looks like.
The same 7 segment displays are available in multiple colors. Like the number can be displayed in GREEN, RED, YELLOW, etc.,
The same 7 segment is customized by different manufacturers to have broad sizes and multiple digits.
LCD Display:
LCD is short form of Liquid Crystal Display and there are several models in the LCD displays. These displays are based on the liquid crystal to produce visible elements. They depend on the reflection from the elements and doesn't emit light directly. One of the common display used by students, hobbyists and engineers is the 16x2 Alphanumeric LCD display.
The LCD above is a single color and comes with different back light colors like BLUE, GREEN, WHITE. There are graphical displays available as well which can display images along with the alphanumeric characters.
128x64 is the very common size used in graphical displays, where as other sizes like the 240x128 are also available.
Apart from the above, there are other LCD types which are used fro commercial applications like the mobiles, tabs, laptops, etc., those include the larger display sizes and are categorized under various types which include:
- Twisted nematic (TN)
- Twisted Film Transistor (TFT)
- In-plane Switching (IPS)
IPS panels provide better viewing angles, better contrast.
Below is an example of TFT LCD display commonly seen in embedded applications:
Below is an example of IPS display with LVDS interface. This is used for applications like Tablet, digital photo frame, etc.,
As we move from simple alphanumeric LCD to displays like IPS LCD, touch screen with single touch and multi touch options come into picture and adds more complexity to the circuit with touch controller also to be included. Even the LCD drivers become complex and sometimes require translation between various protocols.
There are other displays available with the SPI and I2C interface as well.
LED Display:
LED technology is a superior technology and LED displays like the OLED are the most dominating displays in the smart TV segment. LED displays have superior performance than LCD displays. From the most costly displays to the simple dot matrix. Below are the dot matrix LED displays.
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