System-Level Functionality
Integrating a display into your embedded system can be a tricky task. Fortunately, a variety of modular display systems are available today in all shapes and sizes. These solutions provide high-resolution screens with touchscreen capabilities
and rich interface support.
While it’s true that not all embedded systems require any kind of human interface, there’s a large segment that do. In fact, the sphere of applications that can accommodate high-resolution, touchscreen display technologies keep expanding thanks to the availability of easy-to-integrate display modules designed for embedded use.
Over the past 12 months, display module vendors have developed a variety of new solutions providing smaller sizes, enhanced performances, new levels of ruggedness and rich sets of interface support. Support for Raspberry Pi and improved e-paper displays are also part of the latest display trends. So that you don’t have to face the complexity of interfacing a raw display with an embedded computer system, today’s crop of display modules either make such integration easy, or provide complete pre-integrated display-computer subsystems.
HDMI FOR EMBEDDED
While HDMI display connectivity has become standard in consumer displays, it was slower to move into the embedded space. Now it’s become entrenched in the embedded realm, with many display module vendors offering next-generation solutions. Along these lines, in September last year, Newhaven Display announced an expansion to its HDMI TFT product line to include two new 10.1″ modules. These display modules feature the company’s 10.1″ TFT paired with a custom PCB designed for HDMI compatibility. The module is available in two options differentiated by a capacitive touchscreen version, and a version with no touch panel (Figure 1). Both options come standard with a durable steel mounting bracket featuring server-rack-height threaded mounting holes.
Both of the 10.1″ HDMI TFT Modules are 1024×600-pixel resolution and sport MVA technology for 75-degree viewing from all angles. The boards on these products also have a Texas Instruments (TI) audio amplifier embedded to enable the use of the audio channel already supported by HDMI. The product provides simple, standard HDMI interfacing.
Similar to Newhaven Display’s other HDMI TFT modules, the process of connecting to the display is designed to be easy. There’s no need to work around any ribbon cables or extra controller boards. Embedded system developers can just connect a standard HDMI cable directly to the TFT Module. Setup for the capacitive touch panel version is easy as well. You connect the touch panel via USB cable and the USB-HID driver recognition will quickly initialize the touch panel for use right away.
The durable steel bracket included with both 10.1″ HDMI TFT options provides a secure and stable way to mount the display within any application. The bracket is server rack-unit height making it an easy fit for standard server racks. These mounting brackets bring a vibration-resistant and reliable method of installation already packaged with the 10.1″ HDMI TFT modules.
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GLOVE TOUCH SUPPORT
The latest TFT module offering from Noritake is its GTWV050VHB00P product, an embedded touch TFT module designed to smoothly integrate into any project. The module consists of a 5″ high brightness TFT panel, digital video interface (DVI) with HDMI connector, 5 VDC single power supply, FLETAS Metallized Projective Capacitive Touch (MPCT) screen and all necessary drive circuitry (Figure 2). The mounted FLETAS touch panel has high touch sensitivity that can operate accurately in demanding environments. Touch works with gloves and up to a 5 mm acrylic overlay (with 0.5 mm air-gap).
The GTWV050VHB00P can work with commonly used micro-USB and HDMI cables. The power supply connector uses a JST SM05B-GHS-TB connector. All connectors are located on the backside of the display module as shown in Figure 2. Touch is supported via USB or I2C and is HID-compliant (no driver required). The module supports wide VGA (800×480 pixels) in 5″ screen size. A high brightness 1,000 cd/m2 5″ TFT panel is used for this design. (Actual brightness: 810 cd/ m2 typical.) The FLETAS MPCT screen has adaptive sensitivity that works with gloved hands, water droplets and thick overlays. Touch sensitivity is adjustable via simple commands over USB, I2C and UART.
RASPBERRY Pi DISPLAY
Raspberry Pi embedded computers have become extremely popular in recent years. And while the technology is often used in hobbyist projects, an ecosystem has evolved around Raspberry Pi providing a wealth of supporting products available for professional embedded system developers. Along just such lines, among the latest offerings from 4D Systems is its gen4-4DPI series of LCD display modules specifically designed to support the Raspberry Pi family of SBCs.
The display modules are available for the Raspberry Pi A+, B+, 3, Zero and Zero W with resistive or capacitive touch control options and provide a compact and elegant HMI display solution. The displays are also powered directly from the Raspberry Pi, eliminating the need for an external power supply. The gen4-4Dpi display modules are available in three screen sizes: 4.3″, 5.0″ and 7.0″—and connect to the Raspberry Pi through a 30-pin FPC cable and an adapter board that conforms to the Raspberry Pi expansion header pin-out and Pi’s HAT device identification standard.
The m GEN4-4DPI-43CT-CLB version of the module features an integrated resistive touch panel or capacitive touch panel, enabling the gen4-4DPi to function with the Raspberry Pi without the need for a mouse. Communication between the gen4-4DPi and the Raspberry Pi is interfaced with a high speed 48 MHz SPI connection, which utilizes an on-board processor for direct command interpretation and SPI communication compression and features a customized DMA-enabled kernel. This combination allows this display to output high frame rate compared to other SPI display solutions, when displaying a typical image/video, and can achieve higher depending if the image can be compressed.
The gen4-4DPi is designed to work with the Raspbian Operating System running on the Raspberry Pi, as that is the official Raspberry Pi operating system. It is also compatible with Pixel and Scratch. Mounting of the gen4-4DPi is achieved with the 4 mm × 4 mm mounting holes present on the resistive touch display modules, enabling standard screws to fasten the Gen4-4DPi as required, or via the adhesive supplied on the cover lens bezel, which is part of the capacitive touch version.
E-PAPER SCREEN ADVANCES
No longer a newcomer on the embedded scene, electronic paper displays (EPD) continue to evolve, with suitable products designed for embedded needs. Exemplifying that trend, in June Pervasive Displays (PDi) announced its new range of rugged tri-color displays, aimed at use in portable equipment designed for use in demanding conditions. Because such systems are used in in situations where impacts are common, a display’s individual components must be exceptionally robust. Pervasive Displays’ line of rugged black, white and red displays—available in 3.7″, 4.2″, 4.37″ and 7.4″ models—include a resin board attached to the glass substrate to protect the screen from breaking when bumped, dropped or knocked (Figure 3).
Example applications requiring this level of durability are wearable systems, logistics container labels, or tags on moving equipment. Where a conventional glass display could shatter in these situations, these new displays are designed to resist the impact by being up to 50% stronger, helping ensure the screen remains readable.
The display’s ruggedness adds to the already-attractive characteristics of EPDs for use in challenging and/or remote conditions. The way EPDs display text and images, using physical ink particles that reflect ambient light, means they remain readable even in bright sunlight or other harsh lighting conditions. Their near-180° viewing angle further enhances their ease of readability. Moreover, their exceptionally low-energy demands mean they don’t require grid power, and are instead able to run for months or even years using a small coin cell battery.
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The rugged displays’ built-in timing controller (iTC) also minimizes the need for peripheral circuitry, resulting in smaller overall devices or extra space for batteries and other components. The displays’ high pixel density—ranging from 117 dpi to 130 dpi, depending on the screen size—state-of-the-art driving waveform and the ability to render both text and images in red, white and black, mean embedded system designers can display rich, sharp and detailed information to users.
FANLESS PANEL PC
So called Panel PCs are a category of display systems that tend to be larger and are meant to be mounted on a factory wall or on the side of an industrial machine. An example along those lines is Axiomtek’s the GOT810-845, a 10.4″ stainless steel fanless touch panel computer powered by the Intel Celeron processor N3060. The rugged touch panel PC has an XGA TFT LCD display with 350 nits of brightness, as well as two touchscreen options: 5-wire flat resistive touch and projected capacitive multi-touch (Figure 4).
The customizable GOT810-845 is designed for operation in industrial and outdoor environments with its IP66/IP69K-rated enclosure and IP66-rated M12-type connectors, making it well suited for food processing and heavy-duty applications that require ruggedness and water/dust resistance for harsh operating conditions.
The GOT810-845’s five IP66-rated M12- type I/O connectors are located at the rear bezel and include one Gbit Ethernet port, one RS-232/422/485 port, one RS-232 port, two USB 2.0 ports and one DC power connector. For operational reliability, it can operate under wide temperature settings ranging from -10°C to +50°C and withstand vibration up to 2 G.
The expandable touch panel computer has two PCI Express Mini Card slots for wireless connectivity through 3G, 4G and LTE. The GOT810-845 comes with one DDR3L-1333 SO- DIMM for up to 8 GB of system memory, as well as one mSATA and one SATA for storage. It runs on Windows 7, Windows 8/8.1 and Windows 10 operating systems. 
RESOURCES
4D Systems | www.4dsystems.com.au
Axiomtek | www.axiomtek.com
Newhaven Display | www.newhavendisplay.com
Noritake | www.noritake-elec.com
Pervasive Displays | www.pervasivedisplays.com
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • AUGUST 2019 #349 – Get a PDF of the issue
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Jeff served as Editor-in-Chief for both LinuxGizmos.com and its sister publication, Circuit Cellar magazine 6/2017—3/2022. In nearly three decades of covering the embedded electronics and computing industry, Jeff has also held senior editorial positions at EE Times, Computer Design, Electronic Design, Embedded Systems Development, and COTS Journal. His knowledge spans a broad range of electronics and computing topics, including CPUs, MCUs, memory, storage, graphics, power supplies, software development, and real-time OSes.
