When designers choose displays for industrial control, medical equipment, and other compact systems, they not only need to display more information on smaller screens, but also need to improve visibility, usability, and reliability. In addition, it is necessary to reduce costs while accelerating development.
It is difficult to achieve a reasonable combination of size, resolution, brightness, and industrial performance when using traditional solutions. So, the problem becomes the difficulty level of integration. Small industrial displays typically take the form of display panels or modules, but require designers to spend a lot of effort addressing issues such as low-level drivers, backlighting, and electromagnetic interference (EMI) mitigation.
This article first briefly introduces the challenges that designers face when developing compact systems. Then introduce Newhaven Display's 3.5 "high-definition plug and play display, and demonstrate how to quickly integrate and deploy this display.
The demand for compact high-resolution display screens in the market continues to grow
Small devices have always been able to barely use low resolution displays. Due to functional limitations, these traditional systems only require simple menus and basic indicator labels. However, modern devices require high-resolution displays to present complex data and achieve a perfect user experience.
The introduction of Internet of Things (IoT) connectivity and complex analytics capabilities has driven these changes. Taking portable diagnostic tools and measuring devices as an example, the functions of such devices go far beyond providing feedback measurement data. They also need to output in-depth performance analysis of device operation and provide visual operation guidance during troubleshooting.
The development of platforms has also driven the demand for resolution. As traditional embedded RTOS environments give way to modern platforms such as Linux, Windows Embedded, and Raspberry Pi, designers face a practical limitation: modern operating systems require a display resolution of at least 640 × 480, which traditional small device displays simply cannot meet.
From a development perspective, reusing user interface frameworks, widgets, and icon libraries originally developed for desktops, tablets, or embedded systems with higher resolution has become a reality. This reuse helps ensure consistency in branding and features across product lines, while avoiding one-time low-level graphical user interface (GUI) work.
Why traditional small displays make integration complex
To meet these demands, designers are shifting from the common 320 × 240 resolution in small displays to clear and responsive 640 × 480 thin-film transistor (TFT) displays, and adopting technologies such as in-plane switching (IPS) to achieve precise colors and wider viewing angles. The four fold increase in pixel count has brought about an excellent user interface, but it has also led to two interrelated challenges.
High resolution displays under 5 inches are usually provided in bare screen form and can be connected through interfaces such as 24 bit RGB, LVDS, or MIPI-DSI. To integrate these display screens, designers must address issues such as high-speed circuit design, complex wiring, and EMI generated by high-frequency signals. Similarly, the backlight of small display screens is usually only the "most basic" configuration, so designers need to purchase LED drivers themselves and implement dimming control functions.
In terms of software, naked screens lack standardized discovery mechanisms. Designers must manually configure display timing and develop customized drivers for touch input and backlight control. However, completing this task requires specialized knowledge of graphics and operating systems, which may not be the core focus of the product team and can make testing, manufacturing, and on-site maintenance more complex.
Simplify the integration of small display screens using HDMI and USB
Newhaven Display's 3.5 "IPS HDMI TFT display (Figure 1) integrates a 640 × 480 display panel, high brightness backlight driver, EMI shielding structure, and optional capacitive touch module into a complete display component, easily resolving the aforementioned issues. The pixel density of these display panels is 228 pixels per inch (PPI), meeting the resolution requirements of information intensive human-machine interfaces (HMI) and avoiding the troubles of traditional hardware design.
Newhaven Display's 3.5 "IPS HDMI TFT Display Screen
Figure 1: The 3.5-inch IPS HDMI TFT display integrates a clear 640 × 480 display panel into a complete plug and play component. (Image source: Newhaven Display)
The interface software for HDMI video can simplify system debugging. In terms of the host system, this display screen is like a standard HDMI monitor, rather than an unknown bare display panel that requires a customized timer. Like any standard HDMI monitor, this interface declares 640x480 mode through Extended Display Identification Data (EDID) and can achieve automatic detection on common single board computer (SBC) platforms such as Windows, Linux, and Raspberry Pi. In this way, there is no need to develop low-level graphics drivers, and the risk of resolution configuration errors can be minimized to the greatest extent possible.
The touch sensitive NHD-3.5-HDMI-HR-RSXP-CTU (Figure 2) extends the design concept of the standard interface to its projected capacitive (PCAP) touch input. In this capacitive touch product, the micro USB connector can provide both 5V power and touch data simultaneously. Touch controllers display as standard USB Human Interface Devices (USB-HID) on Windows and Linux systems, so the operating system automatically installs their drivers without requiring specific vendor kernel modules.
Newhaven Display NHD-3.5-HDMI-HR-RSXP-CTU (click to enlarge)
Figure 2: NHD-3.5-HDMI-HR-RSXP-CTU integrates a clear 640 × 480 display panel into a complete display assembly, and EMI shielding devices are installed around the high-frequency components. (Image source: Newhaven Display, modified by the author)
These modules also simplify the entire assembly process. When using a bare display panel solution, designers need to perform multi-step integration: installing TFT glass in a customized frame, fixing independent driver boards in other positions inside the housing, laying precision ribbon cables between components, and determining the installation space for the discrete LED driver circuit. The 3.5 "IPS HDMI TFT simplifies the above process and can be assembled only through the mounting holes located at the four corners.
The dual cable architecture (HDMI for video, Micro USB for power and touch) replaces fragile flexible circuits with standard cables, and connectors are arranged along one edge of the printed circuit board (PC board) for easy direct wiring. The integrated EMI shielding structure further reduces the anti-interference requirements at the shell level.
Using IPS technology to achieve visibility under sunlight
Compared with traditional twisted nematic (TN) or vertical alignment (VA) display panels, IPS displays have excellent optical performance. IPS achieves an 85 ° wide viewing angle in all directions and maintains consistent color and contrast across different viewing angles. The typical brightness of the capacitive model is 810 candles per square meter (cd/m ²), which supports use in strong ambient light environments, making handheld instruments, control panels, and other applications in outdoor and industrial environments clearly visible.
The non touch NHD-3.5-HDMI-HR-RXP display screen (Figure 3) adopts the same overall architecture, but eliminates PCAP overlap. This results in a display brightness of 950 cd/m ², providing better readability under sunlight for applications that process input through physical buttons or other external controllers. The current consumption of non touch models is also slightly lower (typical value is 460 milliamps (mA) instead of 490 mA). This model also uses HDMI and USB connection methods, but USB only provides power.
Newhaven Display's NHD-3.5-HDMI-HR-RSXP display screen, with specific dimensions marked in the picture (click to enlarge)
Figure 3: The NHD-3.5-HDMI-HR-RXP model pre integrates a 640 × 480 display screen and adopts a bezel opening design instead of a capacitive touch configuration. (Image source: Newhaven Display, modified by the author)
The working temperature range of both models is -20 ° C to+70 ° C, and the storage temperature range is -30 ° C to+80 ° C. Verification tests include thermal cycling, vibration, and electrostatic discharge, with a test voltage of ± 8 kV in air and ± 4 kV in contact. These characteristics enable both products to be deployed in industrial, transportation, and light outdoor environments, and designers do not need to carry out display level certification themselves.
Quickly start hardware and software settings
At the hardware level, integration mainly focuses on three main interfaces (Figure 4). HDMI A-type connector is used to provide video input; The USB Micro-B connector is used to provide 5V voltage, and if it is a capacitive model, it can also transmit USB-HID touch data. The small terminal block leads out the backlight driver control pin, which can accept simple enable signals or pulse width modulation waveforms from 5 kHz to 100 kHz. The LED status indicator light can indicate power, HDMI link detection, and capacitive version touch actions, which are helpful for startup debugging and on-site troubleshooting.
The main functions of Newhaven Display 3.5 "IPS HDMI TFT
The main features of IPS HDMI TFT in Figure 4:3.5 include HDMI (1) and USB Micro-B (2) interfaces, HDMI, DC power supply, touch detection LED indicator lights (3-5), and backlight terminal block (6). (Image source: Newhaven Display)
In Windows 10 and 11 systems, the display screen will be automatically detected as a regular HDMI monitor. Once the USB link is connected, the capacitive model will be listed as a USB-HID touch device. No need to install dedicated drivers, standard display settings and touch calibration tools can be used.
Linux based systems typically use HDMI and EDID for automatic mode detection in a similar manner. In most configurations, the module displays as a standard HDMI monitor and the system automatically selects the 640 × 480 mode. For platforms such as Raspberry Pi, the user guide provides examples of configuration statements to force the use of the desired mode and timing when necessary. The touch input of the capacitive version display screen is displayed as a USB-HID device through the standard Linux input subsystem, simplifying integration with common graphics frameworks.
The backlight brightness can be adjusted through the control pins of the integrated LED driver without the need for a separate driving circuit. Static logic levels can be used for simple on/off control, while pulse width modulation inputs can adjust brightness to adapt to low light environments or reduce idle power consumption. This method avoids the switching noise and layout complexity caused by the design of discrete high-voltage LED drivers on the main circuit board.