Heart Rate 11 Click is a compact add-on board suitable for heart rate monitoring applications. This board features the OB1203, a multi-channel light sensor (LS/CS), a proximity sensor (PS), and a photoplethysmography sensor (PPG) from Renesas. It can be configured as an ambient light sensor to measure ambient light similar to the human eye experience or as an RGB color sensor. The OB1203 establishes communication to and from the module entirely through a standard I2C compatible interface and has a fully integrated biosensor for reflective photoplethysmography. With the appropriate algorithm, this Click board™ can determine human heart rate (HR), oxygen saturation (SpO2), respiration rate, and heart rate variability (a measure of stress).

Heart Rate 11 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.

Heart Rate 11 Click as its foundation uses the OB1203, a fully integrated all-in-one biosensor module that measures heart rate and blood oxygen levels from Renesas. The OB1203 combines all light sources, drivers, and sensor elements, in a single optically optimized package and can be used with just one side of a user’s finger because it uses the space-conserving reflective PPG method. The appropriate algorithm can determine human heart rate, respiration rate, and heart rate variability (a measure of stress) or blood oxygen saturation (SpO2) behind IR transmissive but visibly dark ink, allowing implementation in aesthetic industrial designs.

The biosensor module contains different photodiodes for light (R, G, B, and Clear channels), proximity measurements, photoplethysmography, and temperature compensation of the light sensor. Those diodes are arranged in a matrix array, while the single diode for PS/PPG measurement is located below the matrix. The current photodiode is then converted to digital values by an analog-to-digital converter (ADC) and then forwarded via a serial interface for further processing.

The OB1203 communicates with MCU using the standard I2C 2-Wire interface with a maximum clock frequency of 400kHz, fully adjustable through software registers. Also, it uses an interrupt pin, the INT pin of the mikroBUS™ socket, indicating when a specific interrupt event occurs, such as light, proximity, or photoplethysmography threshold crossed.

This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.

• Interface: I²C
• Compatibility: mikroBUS™
• Dimensions: 28.6 x 25.4mm
• Input Voltage: 3.3V
• PSpectral Response (R/G/B/C): 610/550/470/520 nm
• PPG Resolution: Min. 16 bits, Max. 18 bits
• AL Sensitivity: Min. 0.06 lux, Max. 150,000 lux
• AL&CS Resolution: Min. 13 bits, Max. 20 bits
• Operating Temperature Range: Min. -40°C, Typ. +25°C, Max. +85°C

• Schematic
• OB1203 Datasheet
• mikroSDK
• GitHub