Nuvoton NuMicro® M451 series microcontrollers, based on the Cortex-M4 core, have an instruction cycle of 72 MHz. It has a set of 12-bit ADC and supports up to 16 channels, and 16-bit PWM can provide 12 outputs, built-in DSP and FPU floating point arithmetic unit, can improve the calculation speed and accuracy of PM2.5. In addition, the M451 series has a wealth of peripheral interfaces, providing 3 sets of SPI interfaces to support external memory devices and TFT-LCD (for data display, and 5 sets of low-power UARTs for connecting various wireless modules, combining data Real-time transmission and collection.M451 series microcontrollers  support operating voltages from 2.5V to 5.5V and industrial-grade operating temperatures from -40°C to 105°C. In addition, the M452 USB series provides 1 set of USB 2.0 FS OTG/Device, and the M453 CAN series provides 1 One set of USB 2.0 FS OTG/Device and one set of CAN 2.0 allow PM2.5 sensors to be combined with more applications.

The recent PM2.5 air pollution detector solution is the Nuvoton Cortex-M4 microcontroller. PM2.5 is a suspended particle containing solid and liquid in the air. The cause may be man-made pollution or natural factors. Being in an area where the PM2.5 concentration is too high will cause a lot of harm to people. Therefore, in recent years, the monitoring of air quality around the world has also included PM2.5 as an important indicator. With the development of technology, air quality testing products have evolved from desktop to portable, and even further integrated into wearable air quality detectors. Some of them also have networking capabilities to upload data to the cloud in real time. At present, most portable detectors use the light scattering element (meter-type scattering) to calculate the PM2.5 concentration. They include a light source control circuit and a fan control interface to adjust the air circulation into the measurement channel to improve accuracy. Therefore, As the main control MCU of PM2.5 sensing device, it must have accurate ADC sampling capability and stable PWM control.

Application reference schematic diagram of PM2.5 sensor development using NuMicro M451 platform