Hear your heart's story with SFH 7060 and STM32L496AG

Heart Rate 9 Click is based on the SFH 7060, a heart rate and pulse oximetry monitoring sensor from ams OSRAM. It utilizes a Phase Division Multiplexing technique to simultaneously measure multiple signals with zero cross-talk. This technique uses the PIC16F1779 MCU's integrated Core Independent Peripherals (CIPs) from Microchip. CIPs allow you to achieve a low-noise reflective heart rate monitor design with significantly lower BOM costs than conventional designs. This Heart Rate 9 Click board™ introduces Microchip's proprietary method (hereafter "proprietary method") of measuring multiple signals in a body using pseudorandom binary sequence generation and phase division multiplexing. This proprietary method uses a special encoding/decoding scheme to allow multiple light-emitting diodes (LED) to transmit light simultaneously with a single photodiode to condition each light from the combined lights at the receiving side. While the blood passes through the capillary blood vessels, they expand and dilate. Their light reflectance index changes accordingly. This is the basis of the photo-plethysmogram (PPM), a method used for the volumetric measurement of an organ, or in this case - blood vessels. The heart rate signal is calculated

according to the changes in the reflected green light sensed by the PD element. The Heart Rate 6 click can provide the HRM readings by placing the index finger over the optical sensor. Oxygen saturation in the blood can be determined by measuring the light absorption in the red/IR part of the spectrum. The oxygen-saturated blood absorbs more red light and less infrared than the unsaturated blood. This fact can be used to determine the oxygen saturation of the blood. The peripheral capillary oxygen saturation (SpO2) percentage ranges from 95% to 100% for a healthy adult. The challenge in a multiple signal sources system (for example, the LEDs in the case of a pulse oximeter) is that each LED must share the same photodiode. A classic solution is to turn on each light source in sequence and then take each measurement in turn. Each light source gets its slice of time in which the photodiode can get its measurement. This method is called Time-Division Multiplexing (TDM). The same principle is also applied to the TDMA-based cellular system. The drawback of the TDM approach is that adding more light sources while keeping the data processing routine the same results in more time to get a measurement from every source. Microchip's proprietary method uses a known

concept called Maximal Length (ML) sequence, a type of pseudorandom binary sequence, to generate a gold code or a reference sequence. This reference sequence is then phase-shifted using PhaseDivision Multiplexing (PDM) to drive multiple LEDs. After passing through a part of a body, the light amplitudes from these LEDs are detected by a phototransistor or photodiode and digitized with an Analog-to-Digital Converter (ADC). The digitized ADC light amplitude values are re-correlated with each LED's driving sequence. Spread spectrum techniques are known for their noise mitigation properties and ability to pass multiple signals through the same medium without interference. Thus, these measurements of each light absorption of the body can be performed substantially simultaneously with minimal interference from each other. The SFH7060, made by ams OSRAM, integrates three green, one red, one infrared emitter, and one photodiode in a reflective package. The reflective photo sensing method has become increasingly popular in developing small, wearable biometric sensors, such as those green light sensors seen in the back of smartwatches or activity tracker wristbands.

The 32L496GDISCOVERY Discovery kit serves as a comprehensive demonstration and development platform for the STM32L496AG microcontroller, featuring an Arm® Cortex®-M4 core. Designed for applications that demand a balance of high performance, advanced graphics, and ultra-low power consumption, this kit enables seamless prototyping for a wide range of embedded solutions. With its innovative energy-efficient

architecture, the STM32L496AG integrates extended RAM and the Chrom-ART Accelerator, enhancing graphics performance while maintaining low power consumption. This makes the kit particularly well-suited for applications involving audio processing, graphical user interfaces, and real-time data acquisition, where energy efficiency is a key requirement. For ease of development, the board includes an onboard ST-LINK/V2-1

debugger/programmer, providing a seamless out-of-the-box experience for loading, debugging, and testing applications without requiring additional hardware. The combination of low power features, enhanced memory capabilities, and built-in debugging tools makes the 32L496GDISCOVERY kit an ideal choice for prototyping advanced embedded systems with state-of-the-art energy efficiency.