Intermediate
30 min

Provide real-time insights into your cardiovascular health using MAXM8616 and MK64FX512VDC12

Unlock your heart's secrets

Heart Rate 2 Click with UNI-DS v8

Published Jun 01, 2023

Click board™

Heart Rate 2 Click

Dev Board

UNI-DS v8

Compiler

NECTO Studio

MCU

MK64FX512VDC12

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

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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

UNI-DS 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 STM32, Kinetis, TIVA, CEC, MSP, PIC, dsPIC, PIC32, and AVR 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, UNI-DS v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the UNI-DS v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it 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 is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. UNI-DS 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.

UNI-DS v8 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Type

8th Generation

Architecture

ARM Cortex-M4

MCU Memory (KB)

640

Silicon Vendor

NXP

Pin count

121

RAM (Bytes)

196608

Used MCU Pins

mikroBUS™ mapper

General Purpose
PB6
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt
PC18
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB2
SCL
I2C Data
PB3
SDA
Power supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

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 UNI-DS 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

This Click board can be interfaced and monitored in two ways:

  • Application Output - Use the "Application Output" window in Debug mode for real-time data monitoring. Set it up properly by following this tutorial.

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

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * \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_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    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 )
    {
        counter++;
        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;
        }
    }
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

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

Additional Support

Resources

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