LCD Display Inverter

“We interact with Human Machine Interfaces (HMIs) every day. Some of these interactions are obvious, such as when touching the home screen of a smartphone or tablet, but the most common HMI environment is actually in industrial applications.

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We interact with Human Machine Interfaces (HMIs) every day. Some of these interactions are obvious, such as when touching the home screen of a smartphone or tablet, but the most common HMI environment is actually in industrial applications.

At various home appliance and consumer electronics fairs held in recent years, we found that more and more home appliances (such as refrigerators, vacuum cleaner robots, cooking stoves and range hoods) have added HMI touch keys and LED animation functions. Driven by this trend, designers are making their products smarter and modern with user-friendly interactive features.

The capacitive sensing technology plays a very important role in realizing the above functions. When designing home appliances, the focus is on reliability, robustness and how to make the product more attractive. With a capacitive touch user interface based on proximity sensing and LED animation reference designs, designers can implement innovative features in home appliances such as preset lighting modes, lower standby power consumption and moisture resistance.

This reference design uses a single MSP430FR2522 microcontroller (MCU) based on CapTIvate™ touch technology and advanced LED driver technology, as shown in the figure below. Each of the six capacitive touch I/O channels has a specific purpose. In this particular design, three are for dial controls, two are for buttons, and one is for proximity sensing. Precise control even with splashes of grease or water droplets.

Block Diagram of Capacitive Touch and LED Animation Reference Design

Another advantage of the MSP430™ CapTIvate MCU is that it can enter a low-power mode with only a few microwatts of standby power consumption, helping to meet product stringent energy efficiency standards or extend battery life. This reference design provides proximity sensing to help the MCU quickly and easily resume from low-power mode to active mode, and the illuminated ring with LED animation provides a great example of attractive and innovative user interfaces in next-generation devices. It is important to have perfect control of the cooktop at all times, for example when there are splashes of water or grease on the cooktop. The very low standby power consumption of CapTIvate MCUs enables designers to meet the highest energy conservation standards.

The LP5569 LED driver features built-in Secure Random Access Memory (SRAM) memory for user programming sequences and three programmable LED engines. Using the integrated engine, preset patterns are stored in program memory so that the LED driver can automatically run blink or color patterns, which makes the MCU’s system resource usage low when running LED animations.

In the capacitive touch user interface based on the proximity sensing and LED animation reference design, the user can use three operating modes:

Proximity Sensing Mode: When a hand approach is sensed, the board will wake up from sleep mode and switch to active mode indicated by the LED.

Autonomy Modes: Pre-stored Autonomy Modes can be selected by key, such as breathing (single color or mixed color fade in, fade out), chase (single color or mixed color), two color chase (one color chase based on another color) or any other pattern programmed by the color designer.

Control Mode: Control Mode demonstrates how the user can control the capacitive dial with their fingers while the app provides feedback through the LED ring.

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With all these features, the next generation of refrigerators or cooktops will be able to detect when a person is near the device and wake up automatically. Users can touch the surface with their fingers and control settings such as temperature and lighting. The interactive panel uses different colors and patterns to indicate various settings, such as the temperature of the freezer or the power of the furnace. Many other applications can benefit from this reference design such as: elevators, thermostats, vacuum cleaner robots or any other product with an interactive user interface.

(Author: Texas Instruments Yuan Tao)