High-resolution touch function man-machine interface in small appliances
We are now seeing an interactive human machine interface (HMI) that supports multi-touch, which is increasingly used in electronic hardware in a variety of modern industries. Technology updates bring a more convenient and extensive control method. Compared to the more cumbersome electromechanical HMIs (such as keypads), multi-touch interactive human-machine interface (HMI) interfaces will be more attractive. And easier to operate. Through this technology, HMI designers can realize that maintaining product consistency and overall aesthetics will greatly enhance the user's perception. The following article will show you how to create a more efficient capacitive touch human-machine interface to meet the many conceptual and technical challenges facing the current engineering team.
The multi-touch function of capacitive touch screens has been widely used in the consumer electronics and computer markets. Now and start to expand to more different areas. One of them is the high-profit home appliance market. Although the touch screen is relatively new interactive technology, in the near future, it has been applied to commodities such as refrigerators, rice cookers, washing machines and the like.
Capacitive touch can sense multiple touch points at the same time, so it can accurately detect various complicated user gestures. In addition to support for multi-touch operation, capacitive touch is more stable than traditional resistive touch screens, because there is no need to apply pressure directly on the screen (plus protective glass when needed), so compared to resistive touch screens, capacitive screens More suitable for demanding work environments in household appliances.
Figure 1: Schematic diagram of HMI for multi-touch washing machines using EVE technology
The schematic diagram of the washing machine in the display module is illustrated in the schematic diagram of FIG. 1, and the user can perform various operations on the high-resolution HMI through multi-touch, and supports various gesture control, such as two-finger touch and flipping pages.丶Page Copy and Paste 丶Resize and long press functions, etc. The main control part is the MM900A1A module with FT900 microcontroller (MCU) as the core. It is connected to FTDI's latest embedded video engine (EVE) FT813 graphics controller through its IO port for screen display.
In addition to the graphics controller, the FT813 demo board features a WVGA resolution LCD display, a 24-bit RGB parallel interface, and an I2C serial interface for the FocalTech touch controller. In addition, the main controller of this MM900A1A module is FT900 high-performance MCU, its SD card can store image content, and a QSPI interface is used to connect to FT813 for HMI control and transfer all image data to LCD display. Instead, the FT900 grabs all touch data and controls the display unit through the user's touch input, and they are connected to related menus such as the main menu submenu 丶 settings and wash progress menu. In the main menu there are scrolling options, scrubbing type properties, selecting settings, washing, keyboard locks, etc. in the settings menu and allowing the user to adjust the brightness and volume to suit their specific preferences. The wash menu includes a progress bar to indicate the different stages of the wash cycle (washing, rinsing, spinning, etc.). All relevant image content is stored on the SD card of the MM900A1A and subsequently downloaded to the FT813 over the QSPI interface.
The FT813 has the ability to track up to 5 touch points simultaneously and to distinguish a total of 255 different objects. Like the EVE series of devices, the FT813 simplifies the architecture of the human-machine interface through its innovative object-oriented architecture. It outputs all audio (tones, beeps, etc.) and images (overlays, fonts, templates, etc.) as simple objects. As a result of this, the image content can be presented in a line-by-line display (with a resolution of 1/16 pixels) instead of a frame buffer that requires a large amount of memory, which can save the cost of a large number of frame buffers. In addition, compared to 32-bit MCUs, cheaper 8-bit or 16-bit MCUs are sufficient, and communication between ICs has changed from a traditional wide parallel bus to a simpler SPI architecture.
The number of parts of the HMI system detailed above will be much smaller than expected, saving not only PCB costs, but also shortening development time due to simple development. Therefore, compared with the traditional multi-touch human-machine interface, this solution not only saves cost but also saves space required. Another important feature is the object-oriented graphics architecture, since all displayed images are treated as objects, and animation is relatively easy to implement with only the coordinates of the updated object. Individual objects can also be displayed in multiple locations without additional creation.
Figure 2: Hardware for HMI implementation - including MM900A1A module and FT813 demo board
The FT813 is one of FTDI's products in the new generation of EVE. Compared to the previous generation, it has a higher resolution, supporting the previous 512 & TImes; 512 pixels to the second generation 800 & TImes; 600 pixels. This means it can provide mainstream display formats (more than 7 inches) for home appliances, and the memory of the new generation has expanded from 256kB to 1MB. The FT813 is available in a compact 56-pin VQFN package.
Multi-touch technology enables people to operate in a more intuitive way, and there is a growing demand in the market. The application examples described in this article will create a highly complex HMI system that can be used in a cost-effective and simple way to create a variety of cool UI solutions. Using EVE's HMI architecture, it can be used not only on MCUs for a variety of different applications, but also significantly reduces board space and component costs.
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