Monitor your heart's health with MAX30101 and PIC18F2685

Keep your heart on track

Published Nov 01, 2023

Click board™

Heart rate 4 Click

Dev Board

EasyPIC v7a

Compiler

NECTO Studio

MCU

PIC18F2685

Stay in tune with your heart's needs and elevate your well-being with our cutting-edge heart rate monitoring technology

Hardware Overview

How does it work?

Heart Rate 4 Click is based on the MAX30101 high-sensitivity pulse oximeter and heart-rate sensor from Analog Devices. The click is designed to run on either 3.3V or 5V power supply. It communicates with the target MCU over the I2C interface, with additional functionality provided by the INT pin on the mikroBUS™ line. The MAX30101 is an integrated pulse oximetry and heart-rate monitor module. It includes internal LEDs, photodetectors, optical elements, and low-noise electronics with ambient light rejection. The MAX30101 integrates red, green, and IR

(infrared) LED drivers to modulate LED pulses for SpO2 and HR measurements. The LED current can be programmed from 0 to 50mA with proper supply voltage. The device includes a proximity function to save power and reduce visible light emission when the user's finger is not on the sensor. The MAX30101 has an on-chip temperature sensor for calibrating the temperature dependence of the SpO2 subsystem. The temperature sensor has an inherent resolution of 0.0625°C. Oxygen-saturated blood absorbs light differently than unsaturated blood. Pulse

oximeters measure the oxygen saturation in one's blood. Or, more precisely, the percentage of hemoglobin molecules in blood saturated with oxygen. These readings go from 94% to 100% in a healthy adult. Since oxygen-saturated blood absorbs more infrared light than red light, and unsaturated blood absorbs more red light than infrared light, the SpO2 readings are calculated by comparing the amount of these two types of light. It is best to use your finger for measurement.

Features overview

Development board

EasyPIC v7a is the seventh generation of PIC development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has a broad set of unique functions, such as the first-ever embedded debugger/programmer over USB-C. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7a allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of the EasyPIC v7a 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 various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-

established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC v7a 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.

Microcontroller Overview

MCU Card / MCU

Architecture

PIC

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

3328

Used MCU Pins

mikroBUS™ mapper

RST

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

Interrupt

RB1

INT

I2C Clock

RC3

SCL

I2C Data

RC4

SDA

Power Supply

Ground

GND

Take a closer look

Schematic

Step by step

Project assembly

EasyPIC v7a front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v7a as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

Rotary B 2 Click front image hardware assembly

EasyPIC v7a MB 2 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

EasyPIC PRO v7a Display Selection Necto Step 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.

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.

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".

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.

Software Support

Library Description

This library contains API for Heart Rate 4 Click driver.

Key functions:

heartrate4_get_intrrupt - Function is used to read desired interrupt specified by flag
heartrate4_get_red_val - Function is used to read the oldest RED value
heartrate4_enable_slot - Function is used to determine which LED is active in each time slot

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 HeartRate4 Click example
 * 
 * # Description
 * This example demonstrates the use of Heart rate 4 click board.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initalizes I2C driver, applies default settings, and makes an initial log.
 * 
 * ## Application Task  
 * Reads data from Red diode and displays the results on USB UART if the measured data
 * is above defined threshold, otherwise, it displays desired message on the terminal.
 *
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "heartrate4.h"

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

static heartrate4_t heartrate4;
static log_t logger;

static uint32_t red_samp = 0;
static uint8_t counter = 200;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    heartrate4_cfg_t cfg;

    /** 
     * 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.

    heartrate4_cfg_setup( &cfg );
    HEARTRATE4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    heartrate4_init( &heartrate4, &cfg );

    Delay_ms( 100 );
    heartrate4_default_cfg( &heartrate4 );
    Delay_ms( 100 );
}

void application_task ( void )
{
    if ( heartrate4_get_intrrupt( &heartrate4, 1 ) & 0x40 )
    {
        red_samp = heartrate4_get_red_val( &heartrate4 );
        counter++;
        
        // If sample pulse amplitude is not under threshold value 0x8000
        if ( red_samp > 0x8000 )
        {
            log_printf( &logger, "%lu\r\n", red_samp );
            Delay_ms( 1 );
            counter = 200;
        }
        else if ( counter > 200 )
        {
            log_printf( &logger, "Place Finger On Sensor\r\n" );
            Delay_ms( 100 );
            counter = 0;
        }
    }
}

void main ( void )
{
    application_init( );

    for ( ; ; )
    {
        application_task( );
    }
}


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