Texas Instruments (TI) System Application Manager Sunil Oak recently published an article entitled "Using Capacitive Touch Technology to Simplify the Human-Machine Interface of Smart Audio", the full text is as follows:
OverviewIn the near future, smart speakers and home assistants will be everywhere. According to data from Juniper Research, by 2022, more than 70 million American homes will install at least one smart speaker.
Since its first launch in 2015, the functions of smart speakers have been significantly improved. Speakers can deliver audio content to users, which is still the main reason why consumers buy one (or more) speakers for their homes. These speakers are equipped with a voice-activated digital assistant to maintain "communication" with users. The other physical controls on the speakers must maintain simple characteristics while still enabling the required functions. These controls include simple power ON/OFF buttons, volume control sliders/wheels, buttons to skip or repeat tracks, microphone mute buttons, etc.
Thanks to voice wake-up commands such as "Alexa", "Hey Siri" and "OK Google", voice has become very popular as a means of interacting with devices. One of the main reasons why smart speakers can be quickly sought after by consumers is that it can fundamentally simplify the process of interacting with them. There are very few buttons for basic functions, and most of them interact through voice commands.
Leonardo da Vinci once said that "the most complex goes to the most simple." Applying this design concept in the 21st century means that the human-machine interface should be simplified as much as possible, and an intuitive design style needs to be maintained. In addition, because voice is the preferred interface, designers must highlight obvious differences in the interface design process. Figure 1 is a traditional smart speaker HMI.
Capacitive touch function allows designers to use unique features in product design and make products stand out in a highly competitive market. This article will introduce how to use the Texas Instruments (TI) MSP430â„¢ microcontroller (MCU) with CapTIvateâ„¢ touch technology to achieve differentiated functions.
MSP430â„¢ capacitive touch sensing MCU with CapTIvate technologyTI MSP430 MCU adopts CapTIvate technology, which makes the touch design have an integrated capacitive sensing peripheral with rich functions. The peripheral uses a highly reliable and ultra-low power design without affecting the touch function, making it an ideal choice for battery-powered applications with a smooth HMI. The configurable CapTIvate peripherals also support self-capacitance and mutual capacitance measurement topologies, allowing designers to take advantage of each topology in the design of the same unique interface with a single MCU. The full-featured programmable MCU that can withstand high-decibel noise and a comprehensive ecosystem make the MSP430 MCU with CapTIvate technology stand out from many capacitive touch controllers.
The MSP430 CapTIvate MCU can significantly improve the potential functions of smart speakers in the following ways:Mechanical button replacement. As consumers become more comfortable with capacitive touch buttons on products, embedded system designers are beginning to realize the benefits of using capacitive touch buttons instead of mechanical buttons. For example, you can use capacitive touch buttons instead of four buttons on a smart speaker, and use a single MSP430 CapTIvate MCU to perceive each capacitive touch button. This can greatly save the cost of the button, the cost of manufacturing the top surface of the cut button, and the cost of simplifying the assembly process.
Advanced input, such as slider and scroll wheel MSP430 CapTIvate MCU enables system designers to use advanced input mechanisms, such as slider and scroll wheel, to control different functions on the device. For example, tapping can turn the microphone on and off, sliding the slider can skip or rewind the audio track, and the rotary touch action on the wheel sensor can increase or decrease the volume. If there is no capacitive sensing controller, it cannot provide support for these gesture mechanisms. This training video introduces some 3-D gestures on the MSP430 CapTIvate MCU.
Close detection. MSP430 CapTIvate MCU also has a close-range detection function, so that as long as the user puts his hand near the device, the LED ring can be turned on and/or greeting the user. This technology provides an amazing enhancement for smart speaker design.
Enhance aesthetic effect. No need to cut the button hole on the top surface is another significant advantage: the designer can design flexibly to make the surface appear more beautiful. It does not even need to keep the surface completely flat; creative designers can experiment with different shapes and materials to adopt designs that enhance functionality and attractiveness to maximize the favor of the market. MSP430 CapTIvate MCU can realize metal touch, glass touch, wood touch and plastic touch.
Improve reliability. The reliability of touch and proximity detection is the key element to maintain the simplicity and simplicity of the smart speaker HMI. Many noise sources pose a serious challenge to reliably detecting capacitive touch. Smart speakers usually have Wi-Fi® and/or Bluetooth® connections, which can increase electromagnetic noise. MSP430 CapTIvate MCU combines signal processing algorithms, low-noise hardware design and noise avoidance technology to ensure that the product has excellent noise immunity. CapTIvate technology uses an integrator-based charge transfer engine equipped with a frequency hopping oscillator, parasitic capacitance correction and spread spectrum clock modulation to improve noise immunity. The CapTIvate software library provides several signal processing algorithms to improve the robustness of touch or proximity detection. This includes multi-frequency algorithms, infinite impulse response (IIR) filters, anti-bounce mechanisms and dynamic threshold adjustments. This reference design shows a noise-tolerant capacitive touch HMI design, and the video also introduces all the noise-resistant features of CapTIvate MCUs.
Anti-moisture function. People have been using traditional Bluetooth speakers in bathrooms, kitchens and swimming pools for some time. We expect smart speakers to follow suit, but this means increasing the moisture resistance of smart speakers. It is indeed effective to completely seal the top surface of the capacitive touch controller, so devices with mechanical buttons must take costly measures to be moisture resistant. The MSP430 CapTIvate MCU can reliably perform touch detection or proximity detection in a humid environment. This cool video shows the humidity resistance of the MSP430 CapTIvate MCU.
Low power consumption. Smart speakers with Wi-Fi connection are usually powered by a wall socket, so they usually do not meet the requirements for low power consumption. However, from the user's point of view, this limits the portability of the speaker. Smart speakers are battery-powered, and the device architecture needs to be redesigned while adopting more complex power management solutions to extend battery life. In fact, portable smart speakers produced by some manufacturers have an operating time of about 10 to 12 hours on a rechargeable battery.
The capacitive touch controllers in these devices need to reduce power consumption as much as possible, while still being able to perform touch detection or close-range detection. The MSP430 MCU with CapTIvate technology is the lowest power capacitive touch sensing solution, and the current per button is less than 2μA/avg. MCU also supports wake-up touch or wake-up proximity detection, so you can set most power-consuming processors into deep low-power mode until activated by touch or proximity events. Check out this reference design, which showcases glass low-power touch.
In addition, our new CapTIvate MCU product line introduces capacitive sensing capabilities into cost-sensitive applications. The new MSP430FR2522 and MSP430FR2512 MCUs with integrated capacitive touch can provide up to 16 buttons and proximity sensing functions for voice-activated home automation systems and audio applications. The device is designed for cost-sensitive applications.
The main features and advantages of the new CapTIvate touch MCU:Affordable capacitive touch MCU: Designers can now use the MSP430FR2522 / MSP430FR2512 MCU to add the advantages of capacitive touch and proximity sensing to cost-sensitive applications.
Shorten time to market: Developers can quickly evaluate the capacitive sensing of their applications through the online CapTIvate technical guide and TI E2Eâ„¢ community support, with the help of numerous MCUs, easy-to-use tools, software, reference designs and documents. Brainstorm your own application. Use your own creativity to create your own masterpieces using CapTIvate Design Center in just 5 minutes. For quick evaluation, the CAPKEYPAD BoosterPackâ„¢ plug-in module can now be used. The BoosterPack module can be used with LaunchPadâ„¢ development kit, CapTIvate development kit (MSP-CAPTFR2633) or CapTIvate programmer board (CAPTIVATE-PGMR) to achieve maximum flexibility.
The integrated capacitance sensing technology is part of a complete MCU with 10-bit SAR ADC, GPIO, timer, multiple serial interfaces (I2C, SPI, UART) on the chip, and can be packaged in TSSOP and QFN.
in conclusionTI MSP430 MCU with CapTIvate technology uses the most noise-resistant capacitive sensing technology. The MCU combines buttons, sliders, scroll wheels, and proximity sensor interface configurations, and has ultra-low power consumption, which can create an eye-catching but simple interface. Innovative designers can use this technology to enhance the design of their upcoming smart speakers, thereby further increasing their global coverage on the basis of the huge success already achieved.
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