The Heart of the Matter: Reducing Noise in Wearable Heart Rate Measurement Applications

October 4, 2018 Microchip Technology Inc.

Wearable Heart Rate Monitor Demonstration Features 8-bit PIC Microcontroller with Core Independent Peripherals

Integrating heart rate measurement with other activity and patient compliance measurements into a wearable medical device can be challenging. In these types of applications, the heart rate measurement is typically done with a reflective heart rate monitor. However, despite the use of complex and expensive analog circuits such as Analog Front End (AFE) chips, most reflective heart rate monitors still generate significant noise, which can affect the accuracy of heart rate measurements. Designers need a more cost-effective method for improving the Signal-to-Noise Ratio (SNR) and getting more accurate measurements with their innovative wearable devices.

Microchip’s Wearable Heart Rate Monitor Demonstration* uses a single 8-bit PIC microcontroller (MCU) to measure heart rate. It utilizes a Phase Division Multiplexing technique developed by Microchip’s application engineers to simultaneously measure multiple signals with zero cross talk. This technique is implemented using an eXtreme Low Power (XLP) PIC16F1779 MCU and its integrated Core Independent Peripherals (CIPs). Using the CIPs can reduce both power consumption and software overhead, thereby allowing you to achieve a low-noise reflective heart rate monitor design that offers significantly lower BOM costs than conventional designs.

The PIC16F1779 offers a high level of integration of Intelligent Analog and digital peripherals, making it well suited for a wide range of applications. Here are some of the key features that make it an excellent choice for this wearable heart rate monitor application:

• Internal clock speeds from 32 MHz to 31 kHz
• Four op amps
• Four 10-bit Digital-to-Analog Converters (DACs)
• Four 5-bit DACs
• Eight high-speed comparators
• 10-bit Analog-to-Digital Converter (ADC) with 28 channels

• Zero-Cross Detect (ZCD)

• Four Programmable Ramp Generators (PRGs)
• Four Complementary Output Generators (COGs) • Four Configurable Logic Controllers (CLCs)
• Peripheral Pin Select (PPS)
• Capacitive touch capability
• eXtreme Low Power (XLP) technology

Development Made Easy

If you are interested in developing a wearable heart monitoring application, go to the Wearable Heart Rate Monitor Demonstration page to get more information. Start with the free download of the user guide, schematics and ‘C’ source code that can easily be modified to your specific application needs. Please note that this demo design is a working electrical proof of concept demonstration only. You will need to develop the mechanical and industrial sensor housing designs that will be necessary to create a complete wearable device. Contact your local Microchip sales representative to see a working example of the Wearable Heart Rate Monitor Demonstration.

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