Industry Article

Overcoming LCD HMI Challenges with Smart LCD Displays

May 27, 2022 by Qiang Dong, Topway

Learn about some of the challenges for liquid crystal display (LCD) touch-screen human-machine interface (HMI) designs and how a designer might integrate them.

HMIs are often used in applications ranging from rugged industrial controls to highly-sensitive medical devices. Most modern HMIs use touch-screen LCDs to allow users to view and interact with important data. While LCDs typically work exceptionally well in this area, there are some drawbacks to their use. Most notably, challenges lie in the time required for the design, coding, and testing of the display. 

Smart LCDs, such as the one shown in Figure 1, attempt to meet these issues head-on.


Example of a small 3.5-inch smart LCD display.

Figure 1. Example of a small 3.5-inch smart LCD display. Image used courtesy of Topway.


This article will aim to explain some of the challenges facing LCD touch-screen HMI designs, as well as how a designer might integrate them.


LCD Touch-screen HMI Development Challenges

Engineers responsible for the design and implementation of touch-screen LCDs for HMIs face several major hurdles. The first, perhaps most challenging and time-consuming problem is the code development and testing stage. 

This stage in the development process can easily take months and may require extensive programming skills. The time required to develop and test code naturally extends development time and time-to-market. GUI design, display configuration, and touch-screen functionality can also require significant coding, adding to the already substantial time required for system development and testing. 

Additionally, display circuits and touch-screen circuits must be included apart from the microcontroller unit (MCU), leading to a greater probability of failure as well as increased component count and overall product cost. This can also require additional wiring, wiring harnesses, and testing.

With all the requirements in mind, why would designers still want to develop touch-screen LCDs for HMIs? Generally speaking, a well-designed HMI allows a human to interact with a machine in the simplest, most intuitive way possible. Touch-screen interaction can be extremely intuitive for users, whether it involves tapping a button or dragging through a list of options. 

Touch-screen GUIs make it more likely that end-users will interact correctly with the equipment, even when they may be in a hurry. In many cases, correct interaction not only means getting the most use out of a product but can do so in a safe manner. Additionally, many times those GUIs may require colorful graphics to ensure that the user’s eyes are drawn to the most critical information.

For example, consider LCD HMIs for EV (electric vehicle) charging stations. Users are typically in a hurry and distracted by a myriad of things in their environment (e.g., the roar of nearby traffic, rain, or their electronic devices). Users need to be able to select the right options for their vehicle and interpret available information in a clear, concise manner. An example of such an LCD solution is shown in Figure 2.


LCD module for an EV charger.

Figure 2. LCD module for an EV charger. Image used courtesy of Topway.


In designs such as this, the need for such a solution outweighs issues associated with touch-screen LCDs.However, a question to consider is: what if there is a touch-screen LCD option for HMIs that can address every problem just discussed? The solution: smart LCDs.


Integrating Smart LCDs Into Designs

A smart LCD is a TFT (thin-film transistor) LCD module with an embedded MCU, display engine, and touch controller. Smart LCDs could allow engineers to design and implement HMIs much more quickly than traditional LCDs. In addition, smart LCDs can be exceptionally well adapted for use with HMIs intended for IoT (Internet of Things) applications displaying real-time data. This is, in part, because the embedded MCU makes it possible to efficiently display real-time data rather than mere passive data. 

Figure 3 contains a block diagram showing how a traditional TFT LCD module compares to a smart one in terms of components and encapsulation.


A traditional TFT LCD HMI compared to a smart TFT LCD.

Figure 3. A traditional TFT LCD HMI compared to a smart TFT LCD. Image used courtesy of Topway


There are several features of smart LCDs that can make them particularly useful. For example, the embedded display engine minimizes the workload on the MCU, enhancing the efficiency of its performance, and reducing the overall design cost.

While traditional LCDs require a display circuit, the smart LCD has one built-in, which means no display code needs to be written. Programming is done graphically, which can help eliminate the need for complex, time-consuming, manual code development, as shown in Figure 4. 


Creating a user interface using a smart LCD requires simple drag-and-drop tools and no coding.

Figure 4. Creating a user interface using a smart LCD requires simple drag-and-drop tools and no coding. Image used courtesy of Topway.


Smart LCDs can utilize very high-level programming capabilities via script engines, such as Lua, which use simple serial level commands. 

Since smart LCDs have the display engine and touch control embedded in the display module, the display and touch-screen logic are encapsulated. 

Additional benefits of a smart LCD include:

  • Stronger, more stable EMC (electromagnetic compatibility)
  • No need for a support circuit or the code required for it to function
  • Working prototypes are available in a much shorter time because of the drastically reduced code development and testing workload
  • Reduced BOM (bill of materials) and component count because the MCU, display engine, and touch controller are all embedded

All in all, smart LCDs can often support everything from simple HMIs to complex ones (such as the one shown in Figure 5) without requiring time-intensive, error-prone development.


Smart LCDs can be used in a wide number of IoT applications such as the parallel filter system shown.

Figure 5. Smart LCDs can be used in a wide number of IoT applications such as the parallel filter system shown. Image used courtesy of Topway.


Smart LCD Solutions from Topway

Though we’ve covered some of the challenges for LCD touch-screen HMI design, as well as how a designer might integrate them, one potential solution is Topway’s 7-inch Smart TFT capacitive touch LCD, shown in Figure 6.


The Topway 7-inch smart TFT capacitive touch LCD.

Figure 6. The Topway 7-inch smart TFT capacitive touch LCD. Image used courtesy of Topway.


This solution aims to be suitable for IoT HMI applications, including: 

  • Instrumentation
  • Medical electronics
  • Industrial control
  • Power equipment

As an example application use, one of Topway’s customers was looking for an HMI for an EV charger (as mentioned earlier). In this case, it was installed on China State Grid's charging stations. 

The requirements included: 

  • A real-time data display
  • A high electromagnetic compatibility
  • Backlight
  • Low power consumption 
  • A wide operating temperature range 
  • A highly customized GUI

In addition to those requirements, the engineers developing the charging stations would prefer an HMI solution that does not require extensive coding and time-intensive testing. Such requirements do not apply just to EV charger HMIs, but to applications ranging from highly sensitive and complex chemical process controls to outdoor transportation kiosks.

Aiming to check off all the requirements, especially to ease development strife, all Topway smart LCDs use the straightforward, 5-step procedure illustrated in Figure 7.


The 5-step process for implementing an HMI using a Topway smart LCD module.

Figure 7. The 5-step process for implementing an HMI using a Topway smart LCD module. Image used courtesy of Topway.


The steps are:

  1. Install Topway UI Editor
  2. Import images and design the UI flow
  3. Download to the smart LCD
  4. Power on, display, and test
  5. Connect to host and start viewing real-time data

In addition to all the requirements, the solution also provided:

  • A 32-bit MCU
  • A 1024 x 600 resolution on a 7-inch screen (active area of 154.21 mm x 85.92 mm)
  • Support for remote user interface (UI) design updates through TCP/IP protocol and a built-in RJ45 LAN port
  • LED backlight
  • Operating temperature range of -20 C to 70 C.


Using the Five-step Process and Benefits for LCD HMI Development

The five-step process described above can be just as simple as it looks. 

To develop a simple tachometer, for example, install Topway’s SGTools software onto a computer, start a new project and add a static background image and static text (if desired). Next, drag and drop one of the tachometer elements and configure its basic properties, which include direction, colors, and min/max values. 

Next, configure VP Resource, which is the type of VP to hold the content and is VP_N16 by default, and the VP Address, which is the VP that holds the value. 

Then compile the project and download it to the smart LCD via a mini USB connecting the computer and the LCD. Once the download is complete, remove the mini USB cable, and power on the display. From there, a few simple codes will connect the tachometer to the correct data.

Smart LCDs like the ones from Topway can be an easy, potential solution with no complex coding but all the benefits of using a touch-control LCD HMI with real-time data. 

The elimination of lengthy design, coding, and testing mean a much shorter product development time and a reduced time to market while still supporting complex HMIs that may include a number of interactive control and data display elements. In addition, the number of components is much smaller leading to a lower product cost and less likelihood of failure.

Topway aims to understand the needs of engineers designing modern touch-screen LCDs, especially when those designs involve HMIs for IoT-enabled applications. See its selections here to learn more about its line of smart LCDs.

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