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Texas Instruments: Inject more imagination into the next generation of home appliances

January 03, 2019

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On the day, Yuan Tao of Texas Instruments released a blog post titled "Injecting More Imagination for the Next Generation of Home Appliances."

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

At the various home appliances and consumer electronics fairs held this year, we found that more and more household 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 have made their products more intelligent and modern through user-friendly interaction.

Capacitive sensing technology plays a very important role in achieving 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 design, designers can implement innovative features in home appliances such as preset lighting modes, lower standby power consumption and moisture resistance.

The reference design uses a single MSP430FR2522 microcontroller (MCU) based on CapTIvateTM touch technology and advanced LED driver technology, as shown in Figure 1. Each of the six capacitive touch I/O channels has a specific purpose. In this particular design, three are used for turntable control, two for buttons, and one for proximity sensing. Precise control is achieved even in the presence of splash grease or water droplets.

Figure 1: Block diagram of a capacitive touch and LED animation reference design (Image courtesy of Texas Instruments)

Another advantage of the MSP430TM CapTIvate MCU is its ability to enter a low-power mode with standby power consumption of only a few microwatts to help meet stringent energy efficiency standards or extend battery life. The reference design provides proximity sensing to help the MCU quickly and easily recover from low-power mode to active mode, and the LED-inspired lighting ring provides a good example of an attractive and innovative user interface in next-generation devices. For example, when there are splashes of water or grease on the cooktop, it is important to have perfect control of the stove at all times. CapTIvate MCUs have very low standby power consumption, enabling designers to meet the highest energy efficiency 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 integration engine, the preset mode is stored in program memory so that the LED driver can automatically run the blink or color mode, which makes the MCU's system resource usage low when running the LED animation.

In capacitive touch user interfaces based on proximity sensing and LED animation reference designs, users can use three modes of operation:

• Proximity sensing mode: When sensing the approach of the hand, the board will wake up from sleep mode and switch to the active mode indicated by the LED.

• Autonomous mode: You can select pre-stored autonomous modes by pressing the button, such as breathing (monochrome or mixed color fade in, fade out), chasing (monochrome or mixed color), two color chasing (one color chase based on another color ) or any other color designer programming mode.

• Control Mode: The Control Mode demonstrates how the user can control capacitive dialing with his finger while the application provides feedback via the LED ring.

With all of these features, next-generation refrigerators or cookers will be able to detect when people are close to the device and automatically wake up. The user can gently touch the surface with his finger 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 stove. 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.