Intermediate
30 min

Your heart's storyteller based on the MAX30003 and PIC18LF47K40

ECG excellence for a healthier tomorrow

ECG 3 Click with EasyPIC v8

Published Jul 01, 2023

Click board™

ECG 3 Click

Dev. board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18LF47K40

Experience the next generation of heart monitoring with our ECG solution

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Hardware Overview

How does it work?

ECG 3 Click is equipped with the MAX30003, an ultra-low power, single channel, integrated biopotential AFE, with the ECG and R-to-R detection functionality from Analog Devices. ECG 3 click is used to record a single-channel electrocardiogram. Electrodes can be attached to ECG 3 click via the onboard 3.5mm jack. ECG 3 click uses a three-electrode system, where two electrodes are connected to the positive and negative differential input of the MAX30003 (ECGP and ECGN pins), while the third electrode is connected to the GND. The Click board™ can be used with the cable and electrodes such as these: ECG/EMG cable and ECG/EMG electrodes. In this case, the white electrode is the GND electrode. These voltage impulses are naturally weak and in the range of just a few millivolts. Therefore, any interferences might obscure them, making them undetectable. These interferences might be induced in the human body itself or appear as the result of the activity of other muscles, such as skeletal muscles. The MAX30003 is armed with several methods to reduce these interferences. However, the placement of the measurement electrodes is also crucial for accurate readings. The MAX30003 IC has two differential inputs comprising a single ECG channel. Therefore, the heart can be monitored from a single plane only - the coronal plane. However, this is quite enough for fitness, heart rate monitoring, and similar applications. All the mentioned features are mostly related to conditioning the input signal and protecting the IC from voltage surges, so several types of electrodes can be used. The inputs are equipped with a single-pole, high-pass (HP) EMI filter, with the cutoff frequency set to 2MHz,

as the first defense against the interferences. A set of integrated clamping diodes prevent the ESD surges from reaching the IC and damaging it. The inputs are connected with the electrodes over the protective serial switches, which are turned off by default. When developing your own application, care should be taken to turn these switches ON. However, the mikroSDK library functions included with the Click board™ take care of the proper configuring and initialization. The differential inputs are further amplified by an integrated low-noise, high-impedance instrumentation amplifier (IA) with a fixed gain. The IA section features yet another HP filter that helps to reject movement artifacts generated by skeletal muscles. Depending on the application requirements, a higher cutoff frequency will result in a less accurate ECG signal, but the effects of the motion artifacts will be reduced even more. This frequency is determined by a capacitor between the CAPP and CAPN pins of the MAX30003 IC, which is about 0.04Hz, with the 1uF capacitor used on the ECG 3 click. The recommended range for the HP cutoff frequency is from 0.04Hz up to 4.4Hz. Following the IA section, the MAX30003 incorporates the two-pole low-pass anti-aliasing (LP) filter with a cutoff frequency of 600Hz, which ensures good sampling quality. The programmable gain amplifier is the next section in the signal chain, allowing optimal signal amplitudes to reach the next stage - the sigma-delta 18-bit A/D converter, which ultimately generates the heart rate readings over the SPI interface. Other features of the MAX30003 IC include the self-testing programmable voltage sources and no lead detection. One of the key

features of the AFE is the R - R interval detection. R-wave is a part of the heart rate signal with the highest peak. The distance between the two peaks is closely related to the heart rate and can give a good insight into the shape of the R-wave when no plot is available. Closely matched R - R and BPM values indicate that R waves are quite sharp, without irregularities. Also, the BMP (beats per minute) is an average value, while the R - R interval represents the timing between two peaks. The extensive interrupt engine can trigger the host MCU from various sources, including interrupt events due to lead detection, R-R detection, fast-recovery event, FIFO buffer states, and many more. These interrupt sources can trigger a state change on the interrupt pin (INTB) of the MAX30003 IC. This pin is active-low. The MAX30003 IC requires a clock signal provided by the onboard oscillator. The frequency of the oscillator is 32.768 kHz. However, the Click board™ accepts the external clock signal over the PWM pin of the mikroBUS™, labeled as CLK. Regarding the voltage levels, there is a TXB0106 IC implemented on the ECG 3 Click, allowing it to operate with both 3.3V and 5V MCUs. This IC is a bi-directional voltage-level translator from Texas Instruments. It is a proven solution used on many different Click board™ designs, which transforms voltages of the logic signals (SPI, interrupt, clock) to 1.8V-level signals, which is acceptable for the MAX30003 IC. This allows many different MCUs to be interfaced with the ECG 3 click The logic voltage selection can be done with the onboard SMD jumper labeled as PWR SEL, while the clock source can be selected by another SMD jumper labeled as CLK SEL.

ECG 3 Click hardware overview image

Features overview

Development board

EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. 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, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC 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 DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC 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.

EasyPIC v8 horizontal image

Microcontroller Overview

MCU Card / MCU

PIC18LF47K40

Architecture

PIC

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

3728

You complete me!

Accessories

3-wire ECG/EMG cable comes with a convenient 3.5mm phone jack, and it is designed for electrocardiogram recording. This 1m cable is a practical companion for medical professionals and enthusiasts. To complement this cable, you can also use single-use adhesive ECG/EMG electrodes measuring 48x34mm, each equipped with an ECG/EMG cable stud adapter. These electrodes ensure a seamless experience when paired with our ECG/EMG cable and guarantee reliable ECG/EMG signal transmission for comprehensive cardiac monitoring. Trust in the accuracy and convenience of this setup to effortlessly record electrocardiograms and electromyograms with confidence.

ECG 3 Click accessories image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
SPI Chip Select
RE0
CS
SPI Clock
RC3
SCK
SPI Data OUT
RC4
MISO
SPI Data IN
RC5
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
External clock
RC0
PWM
Interrupt
RB0
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

ECG 3 Click Schematic schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 as your development board.

EasyPIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EasyPIC v8 Access DIPMB 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 DIP 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

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for ECG 3 Click driver.

Key functions:

  • ecg3_get_ecg - Function reads ECG data from FIFO register

  • ecg3_check_status - Function checks a status flag for the desired interrupt

  • ecg3_get_rtor - Function reads Heart Rate and R - R data and calculates HR data to BPM, and RR data to ms

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 Ecg3 Click example
 * 
 * # Description
 * This click is made for ECG and HR, 
 * equipped with an ultra-low power, single channel, integrated biopotential AFE, 
 * with the ECG and R-to-R detection functionality. 
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes SPI interface and performs the all necessary configuration 
 * for device to work properly.
 * 
 * ## Application Task  
 * Reads ECG Data every 8ms and sends this data to the serial plotter.
 * 
 * *note:* 
 * Additional Functions :
 *  - void plot_ecg() - Sends ECG Data to the serial plotter.
 *  - void log_rtor() - Sends Heart Rate and R - R Data to the uart terminal.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "ecg3.h"

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

static ecg3_t ecg3;
static log_t logger;

static uint32_t ecg_data;
static uint16_t rr_data;
static uint16_t hr_data;
static uint32_t meas_time_cnt = 0;

// ------------------------------------------------------- ADDITIONAL FUNCTIONS

void plot_ecg ( )
{
    if ( ecg_data > 50000 )
    {
        log_printf( &logger,"    %lu,       %lu\r\n", ecg_data, meas_time_cnt );
        
        if ( meas_time_cnt == 0xFFFFFFFF )
        {
            meas_time_cnt = 0;
        }
        else
        {
            meas_time_cnt++;
        }
    }
    Delay_ms( 8 );
}

void log_rtor ( )
{
    if ( ( rr_data != 0 ) && ( hr_data != 65535 ) )
    {
        log_printf( &logger,"R - R Interval : %u ms\r\n", rr_data );
        log_printf( &logger,"Heart Rate :  %u BPM\r\n", hr_data );
    }
    Delay_ms( 2000 );
}

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    ecg3_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.

    ecg3_cfg_setup( &cfg );
    ECG3_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    ecg3_init( &ecg3, &cfg );

    ecg3_sw_reset( &ecg3 );
    ecg3_fifo_reset( &ecg3 );
    Delay_ms( 100 );

    ecg3_default_cfg ( &ecg3 );
    Delay_ms( 300 );
}

void application_task ( void )
{
    ecg3_get_ecg( &ecg3, &ecg_data );

    plot_ecg( );
}

void main ( void )
{
    application_init( );

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


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

Additional Support

Resources

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