Heart Rate 10 Click

How does it work?

Heart Rate 10 Click as its foundation uses the MAX86916, a multipurpose optical sensor with applications in Heart Rate (HR) monitoring and as a medical-grade pulse oximeter from Analog Devices. The MAX86916 integrates four LED drivers and BLUE, GREEN, RED, and INFRARED LEDs. The LED current can be programmed from 0mA to 150mA, and pulse width can be programmed from 70μs to 420μs to allow the algorithm to optimize data acquisition accuracy and power consumption based on use cases. Also, the MAX86916 includes a proximity function to save power and reduce visible light emission when the user’s finger is not on the sensor.

The receive path in the MAX86916 is composed of an ambient-light-cancellation (ALC) circuit, a continuous-time sigma-delta ADC, and a proprietary digital filter that rejects slow-changing ambient light including 100Hz/120Hz interference from artificial lights. The ALC is designed to cancel ambient-light-generated photodiode current up to 200μA, allowing the sensor to work in high ambient light conditions. When the ambient light cancellation function reaches its maximum limit, due to overflow from strong ambient light, the output of the ADC is affected, and the Ambient Light Cancellation Overflow interrupt, labeled as INT and routed on the INT pin of the mikroBUS™ socket, is generated to detect this condition.

The MAX86916 does not require a specific Power-Up sequence but requires a supply voltage of 1.8V to work correctly. Therefore, a small regulating LDO is used, the MAX8511 from Analog Devices, providing a 1.8V out of both 5V and 3.3V mikroBUS™ rails.

Heart Rate 10 Click communicates with MCU using the standard I2C 2-Wire interface with a maximum clock frequency of up to 400kHz. It is fully adjustable through software registers, and the digital output data is stored in a 32-deep FIFO within the device. Since the sensor for operation requires a power supply of 1.8V, this Click board™ also features the PCA9306 voltage-level translator from Texas Instruments. The I2C interface bus lines are routed to the dual bidirectional voltage-level translator, allowing this Click board™ to work with both 3.3V and 5V MCUs properly.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the I2C communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

Specifications

Pinout diagram

This table shows how the pinout on Heart Rate 10 Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	INT	Interrupt
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Heart Rate 10 Click electrical specifications

Software Support

We provide a library for the Heart Rate 10 Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on Mikroe github account.

Library Description

This library contains API for Heart Rate 10 Click driver.

Key functions:

• heartrate10_cfg_setup – Config Object Initialization function.
• heartrate10_init – Initialization function.
• heartrate10_default_cfg – Click Default Configuration function.

Examples description

This example showcases ability for device to read Heart Rate with 4 different diodes. There is IR, Red, Green and Blue. You can control every one of them individualy, and change theirs sequence in FIFO register. All leds data is read from FIFO register, it’s 19bit data for every led.

The demo application is composed of two sections :

void application_task ( void ) 
{   
    uint8_t rd_dat = 0;
    heartrate10_generic_read( &heartrate10, HEARTRATE10_REG_INT_STATUS, &rd_dat );
    if ( ( rd_dat & 0x40 ) )
    {        
        uint32_t ir, red, green, blue = 0;
        heartrate10_read_complete_fifo_data( &heartrate10, &ir, &red, &green, &blue );
        log_printf( &logger, "%lu,%lu,%lu,%lurn", ir, red, green, blue );
    }
    Delay_ms( 3 );
}

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on Mikroe github account.

Other mikroE Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.HeartRate10

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.