30 min

Provide real-time insights into your cardiovascular health using MAXM8616 and PIC18F87J50

Unlock your heart's secrets

Heart Rate 2 Click with Fusion for PIC v8

Published Jun 01, 2023

Click board™

Heart Rate 2 Click

Development board

Fusion for PIC v8


NECTO Studio



Take control of your heart health with our intuitive heart rate monitoring solution



Hardware Overview

How does it work?

Heart Rate 2 Click is based on MAXM86161, a complete, integrated optical data acquisition system from Analog Devices ideal for optical pulse oximetry and heart-rate detection applications. It comprises a single optical readout channel and current LED driver DACs that modulate LED pulses for various optical measurements. The LED current DACs have 8 bits of dynamic range with four programmable full-scale ranges of 31mA, 62mA, 94mA, and 124mA. The LED drivers are low dropout current sources allowing for low-noise, power-supply independent LED currents to be sourced at the lowest supply voltage possible, minimizing LED power consumption. The LED pulse width can be programmed from 14.8μs to 117.3μs to allow the algorithms to optimize SpO2 and HR accuracy at the lowest dynamic power consumption dictated by the application. The optical subsystem Heart Rate 2 Click based on MAXM86161 comprises ambient light cancellation (ALC), a continuous-time

sigma-delta ADC, and a proprietary discrete time filter. ALC incorporates a proprietary scheme to cancel ambient-light-generated photodiode currents, allowing the sensor to work in high ambient light conditions. The optical ADC has programmable full-scale ranges of 4μA to 32μA. The internal ADC is a continuous time, oversampling sigma-delta converter with 19-bit resolution. The ADC output data rate can be programmed from 8sps (samples per second) to 4096sps. The MAXM86161 includes a proprietary discrete time filter to reject 50Hz/60Hz interference and change residual ambient light from the sensor measurements. The sensor also includes an optical proximity function which could significantly reduce energy consumption and extend battery life when the sensor is not in contact with the skin. MAXM86161 power to a minimum during situations with no reflective returned signal. It is also intended to reduce the emitted light to a minimum or even below

what the human eye perceives. The native delta-sigma ADC linearity is exceptional. However, the sub-ranging DAC uses a unary architecture with some mismatch between the DAC's unit current sources and the ADC reference current. This mismatch results in some transfer function nonlinearity (XNL) errors when the sub-DAC code transitions. For this reason, the sub-ranging DAC algorithm is designed to minimize DAC transitions by introducing large hysteresis through the overlapping sub-DAC ranges. Consequently, under normal PPG operation, the sub-DAC does not transition, and the linearity of the converter signal is driven entirely by the linear native delta-sigma ADC. In addition to algorithmically reducing the sub-DAC transitions, the MAXM86161 incorporates a self-calibration scheme that can be used to reduce the sub-DAC XNL errors further.

Heart Rate 2 Click top side image
Heart Rate 2 Click lateral side image
Heart Rate 2 Click bottom side image

Features overview

Development board

Fusion for PIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different PIC, dsPIC, PIC24, and PIC32 MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, Fusion for PIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the Fusion for PIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART, USB

HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet are also included, including the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options (graphical and character-based LCD). Fusion for PIC v8 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Fusion for PIC v8 horizontal image

Microcontroller Overview

MCU Card / MCU



8th Generation



MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

General Purpose
Power Supply
I2C Clock
I2C Data
Power supply

Take a closer look


Heart Rate 2 Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Fusion for PIC v8 as your development board.

Fusion for PIC v8 front image hardware assembly
Buck 22 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
v8 SiBRAIN MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
NECTO Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

UART Application Output Step 1

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

UART Application Output Step 2

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

UART Application Output Step 3

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

UART Application Output Step 4

Software Support

Library Description

This library contains API for Heart Rate 2 Click driver.

Key functions:

  • uint8_t heartrate2_generic_read ( uint8_t reg_adr ) - Generic function for reading data.
  • void heartrate2_generic_write ( uint8_t reg_adr, uint8_t write_data ) - Generic function for writing data.
  • void heartrate2_default_configuration ( uint8_t cfg_led ) - Function for setting default config and turning on one led with cfg_led parameter.
  • void heartrate2_read_fifo ( heartrate2_fifo_data_t *fifo ) - Function for reading fifo data and tag values from device.

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

 * \file 
 * \brief HeartRate2 Click example
 * # Description
 * This example demonstrates the use of Heart rate 2 click board.
 * The demo application is composed of two sections :
 * ## Application Init 
 * Initilizes the driver, resets the device, checks the device ID and applies default settings.
 * ## Application Task  
 * Reads the data from Green diode and displays the results on USB UART if the measured data
 * is above defined threshold, otherwise, it displays a desired message on the terminal.
 * \author MikroE Team
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "heartrate2.h"

// ------------------------------------------------------------------ VARIABLES

static heartrate2_t heartrate2;
static log_t logger;
static uint16_t counter = 1000;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
    log_cfg_t log_cfg;
    heartrate2_cfg_t cfg;
    uint8_t rd_stat;

     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, "---- Application Init ----" );

    //  Click initialization.

    heartrate2_cfg_setup( &cfg );
    heartrate2_init( &heartrate2, &cfg );
    log_printf( &logger, "Configuring the module...\r\n" );
    Delay_ms( 1000 );
    heartrate2_set_en( &heartrate2, HEARTRATE2_PIN_HIGH );
    Delay_ms( 100 );
    heartrate2_soft_reset ( &heartrate2 );
    rd_stat = heartrate2_generic_read( &heartrate2, HEARTRATE2_REG_PART_ID );

    if ( rd_stat != HEARTRATE2_DEV_ID )
        log_error( &logger, "---- WRONG ID ----" );
        log_printf( &logger, "Please restart your system.\r\n" );
        for ( ; ; );
    heartrate2_default_cfg( &heartrate2, HEARTRATE2_CONFIG_GREEN );
    log_printf( &logger, "The module has been configured!\r\n" );
    Delay_ms( 1000 );

void application_task ( void )
    heartrate2_fifo_data_t fifo_object;

    heartrate2_read_fifo( &heartrate2, &fifo_object );

    if ( fifo_object.tag == HEARTRATE2_FIFO_TAG_PPG1_LEDC1 )
        if ( fifo_object.data_val > 1000 )
            log_printf( &logger, "%lu;\r\n", fifo_object.data_val );
            counter = 1000;
        else if ( counter > 1000 )
            log_printf( &logger, "Please place your index finger on the sensor.\r\n" );
            counter = 0;

void main ( void )
    application_init( );

    for ( ; ; )
        application_task( );

// ------------------------------------------------------------------------ END

Additional Support