There was a classic scene in the popular drama “Nothing But Thirty,” where the leading female character, Jia Gu, tried to break into the circle of wealthy wives, so she collected high-end drinking water from all over the world and invited them to a “water-tasting party”; even water-drinking became full of rituals. Suppose you pay attention to the well-furnished real estate around you. In that case, you will notice that in addition to the necessities such as refrigerators, laundry machines, and air-conditioners, water purifiers used to ensure drinking water quality has also become necessary. 

In 2022, under the environment of vigorous control, the real estate business entered an ice age; but in 2023, as everything reopens, with the rebound of the property market, water purifier, which is now a necessary accessory for new houses, will start a new trend. As the demand increases, consumers will not only focus on the core functions of water purifiers. Still, they will also have higher demands for the distinctive tasks of water purifiers, including appearances, operation interfaces, control methods, intellectualization, etc. 

The NuMicro^® M254/M256/M258 series microcontrollers released by Nuvoton are highly suitable for water purifier products; this series based on the M23 core supports the Armv8-M instruction set architecture and has LCD drive, capacitive touch control, and USB2.0 FS Device interfaces built-in. Its operating frequency is 48 MHz, with a maximum of 256KB Flash and 32KB SRAM built-in; it operates in an industrial temperature range from -40℃ to 105℃.

It has up to 24 channels of capacitive touch control built-in that can quickly realize intuitive touch control of one button per function. Nuvoton also provides a self-developed touch control calibration tool, so customers can promptly finish calibration during the development and assembly stages. In addition, the touch function also has the feature of waterproof and high anti-interference to ensure that it can identify accurately whether it is in humid environments or places with water stains attached. In addition to the touch control function, the built-in LCD drive is also equipped with a charge pump and internal resistance divider modes, able to support 3V to 5V LCD screens; information such as water temperature and water volume can be read easily through the screen. Regarding security, the M256 series integrated AES-128/192/256-bit keys can provide more security protection for the data transfer of water purifiers. 

This series integrated 1.75V to 5.5V wide operating voltages, provides an excellent signal-noise ratio, and outstanding high anti-interference features (ESD HBM 7KV, EFT 4.4KV), meeting the needs of stability and reliability that smart home appliances have. The entire series of microcontrollers integrated software-tested libraries (STL) certified by IEC60730-1 Class B Annex H can reduce the time user needs to develop MCU security mechanisms and speed up the IEC60730-1 home appliance class B certification. In addition, it can easily realize the self-fault inspection, abnormality detection, leakage protection, empty burning, and over-temperature protection requirements of water purifiers. 

The M256 series development platform, NuMaker-M256SD development board, and the Nu-Link2 Pro debugger/programmer have become excellent product evaluation and development tools. IDEs supported by the development environment include Keil MDK, IAR EWARM, and NuEclipse IDE equipped with the GNU GCC compiler. In addition to standard development environments, Nuvuton provides the LCD view application development tool and the NuSenadj tuning tool exclusively for the touch control function.