How to Choose the Best Display for Your Embedded Device
Published Jul 2, 2021 | Updated Apr 13, 2022
By Risto Avila
Risto Avila, Technology Director @ The Qt Company. Risto is specialized in embedded software development and system integration.
When your embedded device needs a display, that product becomes one of the most important parts of the device. I have helped build hundreds of embedded devices with screens in my career. I share expert tips and my insights for what to consider when choosing one.
In this article:
- Types of embedded displays
- Factors to consider in choosing an off-the-shelf versus a custom display
- What to consider in building or selecting the best display for your device
- Comparison of embedded display technologies
What is an embedded display?
An embedded display is a screen that connects to an embedded device. The screen provides information about how the device is working and allows users to interact with it.
What is an embedded touch screen?
Sometimes called embedded touch, these displays allow users to interact with the device by touching the screen's surface. Smartphones, including the iPhone, were among the first products to use this technology. Retail displays increasingly use embedded touch screens.
What is an LCD in an embedded system?
The basic standard screens for embedded systems might include a liquid crystal display (LCD). Embedded systems use two types of LCD modules: character LCD and Graphic LCD. A character LCD only shows characters and is the simplest and cheapest LCD technology. A graphic LCD is more advanced and displays images.
Off-the-shelf embedded display vs. designing a display
Engineers who want to include a display with an embedded system can design and create a custom model. Or they can use a pre-built model—or "off-the-shelf" display—in their embedded systems.
There are advantages and disadvantages to each kind of display.
Pros and cons of designing your own embedded display
- Advantages of a custom embedded display:
- Provides a custom look: You can design a display to fit the design of the embedded device. This option can be crucial if your device needs physical buttons along with the digital or touch screen buttons. A custom screen also means users have a more integrated and satisfying experience with the device.
- Doesn’t include features you don't want: A custom model won't have unnecessary extras (casework and cameras) that an off-the-shelf display might not offer.
- The display won't go off the market: When you create a display, you can make arrangements with your manufacturer to continue making it while continually improving it. That partnership can last the life of your embedded device, which might be longer than that of some off-the-shelf displays.
- Can be less expensive: Upfront costs to design a display can be high and cost-prohibitive if you're not producing a large number of devices. But per-unit production costs substantially decrease when manufacturing a large number of devices.
- Disadvantages of a custom embedded display:
- Slow to market: Designing a display takes more time and can delay the point at which you can produce your embedded device for the market. You'll need to create drivers for the display controller. You'll also need to do the work to ensure the display can provide basic graphic functions like drawing lines and boxes. Then everything must be tested and debugged. The entire process might add five or six months or more to production time.
- Mechanical design challenges: Developing the mechanical design of the bezel and glass for the embedded display can be challenging. This part takes significant work and precision to produce a product that looks and feels like the best off-the-shelf displays.
- Can initially be more expensive: The work to design and build a custom display will make the display—and the embedded device—more expensive at the outset.
Buying an off-the-shelf display for an embedded device
- Advantages of an off-the-shelf embedded display:
- They've been proven to work well: Off-the-shelf display modules come with components, graphical interface functions, and other components that are already tested and work well.
- Faster to market: Since off-the-shelf displays have been tested and improved and work well, you can usually get your embedded device finished and ready for the market faster.
- Reduced cost: If you are producing a large number of your embedded device, per-unit costs for a custom display might become low enough for them to be more economical. In any other situation, your cost-per-unit is likely to be less expensive with an off-the-shelf display.Advantages of an Off-the-shelf Embedded Display:
"The lower the volume, the less likely it is that you'll do a custom design—that you design yourself," says Burkhard Stubert, an independent software developer and consultant specializing the embedded systems."
- Disadvantages of an off-the-shelf embedded display:
- Consumer perception of your product: An off-the-shelf display that looks different than or otherwise doesn't fit well with your device can be a negative. Consumers can see your product as less finished or professional.
- Display support: An off-the-shelf display may need support from its manufacturer to continue to perform well. The product may also undergo continual changes and development. Those changes, or lack of support, can cause problems when integrating the display into your embedded device.
- Becoming obsolete: Many off-the-shelf displays will have a life of only a few years before consumers expect to replace them with new and better units. That can be a significant problem if you expect your embedded devices to last much longer than that.
Designing Your Own Embedded Display or Buying Off-the-shelf? Advantages and Disadvantages of Each Option
|Design Your Own Embedded Display
|Buy Off-the-shelf Embedded Display
|Custom Look: You can design a display to fit the design of the device.
|Slow Time to Market: Designing a display will take time and delay when your device can be ready for the market.
|Proven: An off-the-shelf display will have been tested, tweaked, and proven to work.
|Poor Consumer Perception: An off-the-shelf display that doesn't seem to fit with the device will make consumers think less of the product and your company.
|No Unneeded Extras: It won't include cameras and other display screen extras that you don't want.
|Mechanical Design Challenges: It can be challenging to design and produce a professional-looking display.
|Faster to Market: Off-the-shelf means you can get your device to the market faster.
|Support Challenges: An off-the-shelf display may need continual support from its manufacturer; lack of good support will cause problems.
|Won't Leave the Market: When you create a display, your manufacturer can continue to make it as long as you need it.
|More Expensive Final Product: The work necessary to produce a good display will increase the total cost of your device.
|Reduced Costs: In any situation where you are not producing thousands of devices, an off-the-shelf display will be less expensive for your device.
|Obsolescence: Some off-the-shelf displays will have a life of only a few years; that could be a problem if you expect the life of your device will be longer.
|Can Be Less Expensive: Upfront costs are high, but per-unit costs are lower if you produce many devices that need the display.
Important factors in choosing a high-quality embedded display
You'll want to consider several factors as you think about building or buying an embedded display. Those factors include safety, how the user will interact with the device, and the device's working environment.
Here are some of the factors to consider when picking an embedded display:
- What the product does and how a user interacts with it
Some embedded devices may only need a basic display that the user doesn't interact with at all—a display showing the level of battery power for the device, for example. Other embedded devices will have a screen that has more user interaction.
"When looking at how a user interacting with the display determines the sophistication of the model I'm choosing. How big does it need to be? What is the type of information it will display? It starts that use case of analyzing how the user is interacting with the system," says Brent Horine, Ph.D., a senior embedded software developer with Hypergiant, which offers AI services integration for ModelOps.
Many displays operate within embedded systems that are critical for safety. Devices include medical equipment, automotive components, and parts in other critical infrastructure. All aspects of your system, including the display, will need to meet certain safety requirements. Be sure to consider safety in all aspects of choosing or building the display for these types of embedded devices.
Touch screen or buttons?
You might choose to have users interact with the screen mainly through physical buttons rather than through a touch screen. Using buttons will be cheaper; touch screens are much more expensive than a simple display. However, physical buttons can wear down and stop working, and most users expect touch screens with devices these days.
"People are just used to touchscreens from their phones," Stubert says. “If users don't have that, they become very impatient. They want to know why the product doesn't work like their phone."
Touch screens also allow engineers to reprogram the display interactions later if they want to change or add features, explains Horine. "Whereas it's hard to add a (physical) button to a system after it's been deployed," he adds.
You'll want to weigh the high cost of a touch screen display versus how much users will interact with it and their expectations.
Some embedded devices may need more than one screen. You can learn more about how Qt can make multiple screens work well for your device. You can also see a Qt demonstration of the future of embedded displays that uses three screens and two operating systems to provide an exceptional user experience.
Off-the-shelf or custom?
Probably the most important early decision you'll make is whether to build a custom display or buy an off-the-shelf model that will work with your device.
Horine says some devices may need a simple LCD that's two inches by one inch. "I can find someone who manufactures that. Then it's just a function of building and doing the interface that's necessary to make it work," he shares.
As I've outlined above, each embedded display choice has many advantages and disadvantages to consider.
A primary consideration, of course, will be cost. You'll want to evaluate the cost of creating a custom display compared to buying one off-the-shelf. You'll also want to look at longer-term costs that come with either option.
Avoiding user distraction
With certain devices and situations, such as vehicles and agricultural and construction machines, you'll want to ensure your device's display is not distracting, explains Stubert.
Some displays in those machines and vehicles may have rotary knobs or joysticks that allow users to control the device. "You have a second method of input, which is important because a touchscreen always means that you have to look where you touch. So, you are distracted, which is not good in vehicles," says Stubert.
To get more details on one case study of using embedded displays, read this article about how a boat manufacturer is dramatically improving its user display.
Working with environmental considerations
Embedded systems within specific devices will experience environments that affect the display. Engineers will want to consider these environments. Might the device and the display get wet often? Will the device experience significant vibrations, like in many machines or vehicles?
For an embedded device within a vehicle with large, vibrating components, Stubert advises, "You need a display that you can screw in tight, or which clicks into place and it's so tight that you can hardly get it out again."
Need for sufficient memory
Displays require resources from the microcontroller or microprocessor in the embedded system. They will need additional memory for example. The microcontroller will have limited memory but must have enough to run the display.
Many embedded devices have limited power they can consume. You need to ensure that the display can do its job while operating within those limits on power?
The working conditions of the embedded device might quickly wear out a display that isn't durable. You'll also want to consider how people will use the screen and how often they might be touching or using it in general. If users will touch the display often, it needs to be able to handle that interaction.
Product lifecycle and support
If you're buying a display off-the-shelf, you'll want to know how long the manufacturer expects it to last. You'll also want to understand the technical support the manufacturer offers if there are operational problems.
Availability of development tools
Custom or off-the-shelf displays will have software within them. You'll want to make sure you can access development tools and other resources to maintain that software.
For an off-the-shelf display, find out how long the manufacturer will be making this particular unit. If you plan to use the screen in a device that you expect to produce for six years or more, you’ll have issues if the display will only be available for three years.
Technical requirements and integration
You will, of course, want to consider how the display operates with your embedded device hardware and operating system.
You will want to consider whether the industry in which people will be using the embedded device has specific operating requirements. Will there be lighting conditions, such as darkness or bright sunlight, that might affect the screen?
Readability, contrast, and viewing angle
Be sure to test how easy it is to read the display in various environments. Consider the contrast between the type of the screen and its background and the angle at which the users will view it, and if that affects their experience.
Does the display need to reproduce colors on the screen to do its job best? If so, you'll want to pay attention to how accurately it shows colors.
No one likes to wait for something to appear on a screen. Think about how quickly the display updates changes in the text or graphics.
If you're buying an off-the-shelf display, does the manufacturer make the display in the sizes you need?
Top embedded displays to visually impress your customers
Qt's Embedded Product Planning and Requirements Guide provides engineers with more details about the top embedded displays. The guide compares key features of the displays to help make your decision easier.
|Thin film transistor liquid
|Quantum light emitting
|1" – 100"
|0.5" – 6"
|1" – 18"
|1" – 10"
display technology. Reliant on backlight to be visible under most conditions (very bright backlights can be used in sunlight).
|Cheaper to manufacture than AMOLED, but higher
current draw and slower to refresh. High current leads
to quicker degradation.
|Great color gamut and readability, although RGB
components degrade unevenly and are subject to burn-in.
|Advantages of AMOLED but eliminates color
instability. Not yet
available in embedded applications although planned by Samsung.
|Usually monochromatic, but some color variants
available. Power consumed only when image changes.
★ is the lowest ranking while ★★★★★ is the highest.
Beyond embedded displays
Displays are an important part of many embedded devices and can often be the most expensive element in your design. Choosing the right one is vital for the success of your device. Once you've selected a display, you'll want to learn how to streamline the user interface design for the embedded device.
Qt helps you build great UI design
Qt Design Studio helps you create beautiful user interfaces once you've chosen the right display for your embedded device. Qt Design Studio closes the gap between designers and developers allowing you to work simultaneously with one unifying framework, one common language, fewer feedback loops, and faster iterations.
The Embedded Product Planning and Requirements Guide
In this guide for IoT and embedded product planning, we examine the most important criteria to consider at the outset, compare a list of the most used technologies, and rate them in easy-to-compare categories.Download