Intermediate
30 min
0

Stay connected to your heart's rhythm with BMD101 and PIC18LF46K80

Cardiovascular clarity: ECG excellence for a healthier you

ECG 4 Click with Curiosity HPC

Published Nov 01, 2023

Click board™

ECG 4 Click

Development board

Curiosity HPC

Compiler

NECTO Studio

MCU

PIC18LF46K80

Elevate your heart's performance with our intelligent ECG solution

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Hardware Overview

How does it work?

ECG 4 Click is based on the BMD101, a highly integrated specialized bio-signal sensing System-on-Chip (SoC) from NeuroSky, which produces heart-monitoring-related ICs and applications. This IC is the third generation of bio-sensors from this company. It features the complete HR and ECG system on a chip: the analog front-end (AFE) section contains a very precise and low-noise instrumentation amplifier (LNA), which allows very low bio-signals generated by the heart to be amplified enough for the 16-bit ADC to be able to sample them. These voltage impulses are naturally weak and in the range of just a few millivolts, even microvolts. Therefore, any external interferences might obscure them. 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. Therefore, the input signal from the electrodes is processed by several filtering sections, both in the analog (HP filter at the input) and digital domain (LP filter at 100 Hz and BP filter for removing the 50/60 Hz hum from the mains). However, the correct placement of the

measurement electrodes is crucial for accurate readings. More about the electrodes and their placement can be found in the blog article, as mentioned above. ECG 4 Click allows several types of electrodes to be used. It supports both stainless-steel and silver-chloride electrode types. The electrodes are used to perform differential measurements of the voltage generated by the heart. 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. The 3.5mm electrodes connector is further protected by two TVS diodes, which prevent electrostatic discharge (ESD) through the SoC and the Click board™. The absence of the electrodes is detectable by the BMD101, which turns the sensor OFF if there is approximately 19 to 25 MΩ between the electrodes. The BMD101 SoC uses the UART interface for communication. The UART interface works at a 57600 baud rate and has 64 bytes of TX FIFO. It uses the 8-1-1 configuration (1 start bit, 8 data bits, 1 stop bit), allowing communication beyond the

host microcontroller. The UART interface could be used with any USB to UART clicks, allowing the PC or smartphone to process and display the HR and ECG data. More information about the UART interface can be found in the datasheet of the BMD101 SoC. However, provided mikroSDK library offers ready-made functions which speed up the software development process. There is a CS pin on the BMD101 SoC, which is routed to the CS pin of the mikroBUS™. This pin should be set to a HIGH logic level to activate the internal power supply. The RESET pin is routed to the mikroBUS™ RST pin. Setting it to a LOW logic level will trigger a RESET of the BMD101. This Click board™ can only be operated with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.

ECG 4 Click top side image
ECG 4 Click bottom side image

Features overview

Development board

Curiosity HPC, standing for Curiosity High Pin Count (HPC) development board, supports 28- and 40-pin 8-bit PIC MCUs specially designed by Microchip for the needs of rapid development of embedded applications. This board has two unique PDIP sockets, surrounded by dual-row expansion headers, allowing connectivity to all pins on the populated PIC MCUs. It also contains a powerful onboard PICkit™ (PKOB), eliminating the need for an external programming/debugging tool, two mikroBUS™ sockets for Click board™ connectivity, a USB connector, a set of indicator LEDs, push button switches and a variable potentiometer. All

these features allow you to combine the strength of Microchip and Mikroe and create custom electronic solutions more efficiently than ever. Each part of the Curiosity HPC development board contains the components necessary for the most efficient operation of the same board. An integrated onboard PICkit™ (PKOB) allows low-voltage programming and in-circuit debugging for all supported devices. When used with the MPLAB® X Integrated Development Environment (IDE, version 3.0 or higher) or MPLAB® Xpress IDE, in-circuit debugging allows users to run, modify, and troubleshoot their custom software and hardware

quickly without the need for additional debugging tools. Besides, it includes a clean and regulated power supply block for the development board via the USB Micro-B connector, alongside all communication methods that mikroBUS™ itself supports. Curiosity HPC development board allows you to create a new application in just a few steps. Natively supported by Microchip software tools, it covers many aspects of prototyping thanks to many number of different Click boards™ (over a thousand boards), the number of which is growing daily.

Curiosity HPC double image

Microcontroller Overview

MCU Card / MCU

default

Architecture

PIC

MCU Memory (KB)

64

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

3648

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 4 Click accessories image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
Chip Reset
RD0
RST
Chip Enable
RA3
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
NC
NC
INT
UART TX
RC6
TX
UART RX
RC7
RX
NC
NC
SCL
NC
NC
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Schematic

ECG 4 Click Schematic schematic

Step by step

Project assembly

Curiosity HPC front no-mcu image hardware assembly

Start by selecting your development board and Click board™. Begin with the Curiosity HPC as your development board.

Curiosity HPC front no-mcu image hardware assembly
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
Prog-cut hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
Curiosity HPC Access 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 image step 5 hardware assembly
Necto image step 6 hardware assembly
Necto DIP image step 7 hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

After loading the code example, pressing the "DEBUG" button builds and programs it on the selected setup.

Application Output Step 1

After programming is completed, a header with buttons for various actions available in the IDE appears. By clicking the green "PLAY "button, we start reading the results achieved with Click board™.

Application Output Step 3

Upon completion of programming, the Application Output tab is automatically opened, where the achieved result can be read. In case of an inability to perform the Debug function, check if a proper connection between the MCU used by the setup and the CODEGRIP programmer has been established. A detailed explanation of the CODEGRIP-board connection can be found in the CODEGRIP User Manual. Please find it in the RESOURCES section.

Application Output Step 4

Software Support

Library Description

This library contains API for ECG 4 Click driver.

Key functions:

  • ecg4_uart_isr - Function performs the uart interrupt routine, reads a data from uart rx buffer and makes a response from the BMD101 device

  • ecg4_enable_ldo_ctrl - Function powers up or down control of LDO (Low Drop Out)

  • ecg4_generic_read - Generic read function

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 Ecg4 Click example
 * 
 * # Description
 * This example reads and processes data from ECG 4 clicks.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes the driver, sets the driver handler and enables the click board.
 * 
 * ## Application Task  
 * Reads the received data and parses it on the USB UART if the response buffer is ready.
 * 
 * ## Additional Function
 * - ecg4_process - The general process of collecting data the module sends.
 * - plot_data - Displays raw ECG data.
 * - log_data - Displays the real time BPM heart rate.
 * - process_response - Checks the response and displays raw ECG data or heart rate (BPM).
 * - make_response - Driver handler function which stores data in the response buffer.
 * 
 * @note
 * Use the Serial Plot application for data plotting.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "ecg4.h"
#include "string.h"

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

static ecg4_t ecg4;
static log_t logger;

static uint8_t response[ 256 ];
static uint8_t row_counter;
static uint8_t row_size_cnt;

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

static void ecg4_process ( void )
{
    int32_t rx_size;
    char rx_buff;
    
    rx_size = ecg4_generic_read( &ecg4, &rx_buff, 1 );

    if ( rx_size > 0 )
    { 
        ecg4_uart_isr( &ecg4, rx_buff );
    }
}

void plot_data ( int16_t plot_data )
{
    log_printf( &logger, "%d;\r\n", plot_data );
}

void log_data ( uint8_t code_val, uint8_t data_val )
{
    if ( code_val == ECG4_HEART_RATE_CODE_BYTE )
    {
        log_printf( &logger, "** Real-time Heart Rate : %d BPM **\r\n", ( int16_t ) data_val );
    }
}

void make_response ( uint8_t *op_code, uint8_t *row_size, uint8_t *rx_buff, uint8_t *row_cnt )
{
    uint8_t idx_cnt;
    
    if ( *row_cnt == 0 )
    {
        row_size_cnt = 0;
    }
    
    response[ row_size_cnt ] = *op_code;
    response[ row_size_cnt + 1 ] = *row_size;

    for ( idx_cnt = 0; idx_cnt < *row_size; idx_cnt++ )
    {
        response[ row_size_cnt + 2 + idx_cnt ] = rx_buff[ idx_cnt ];
    }
    
    row_size_cnt += ( *row_size + 2 );
    row_counter = *row_cnt;
}

void process_response( )
{
    uint8_t cnt;
    uint8_t idx_cnt;
    int16_t raw_data;
    
    idx_cnt = 0;
    
    for ( cnt = 0; cnt <= row_counter; cnt++ )
    {
        if ( response[ idx_cnt ] == ECG4_RAW_DATA_CODE_BYTE )
        {
            raw_data = response[ idx_cnt + 2 ];
            raw_data <<= 8;
            raw_data |= response[ idx_cnt + 3 ];
            
            plot_data( raw_data );
        }
        
        if ( response[ idx_cnt ] == ECG4_HEART_RATE_CODE_BYTE )
        {
            log_data( response[ idx_cnt ], response[ idx_cnt + 2 ] );
        }
        
        idx_cnt += ( response[ idx_cnt + 1 ] + 2 );
    }
}

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    ecg4_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.

    ecg4_cfg_setup( &cfg );
    ECG4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    ecg4_init( &ecg4, &cfg );

    ecg4.driver_hdl = make_response;
    Delay_ms( 500 );

    ecg4_module_reset ( &ecg4 );
    ecg4_enable_ldo_ctrl ( &ecg4, ECG4_ENABLE_LDO_CTRL );

    Delay_ms( 1000 );
}

void application_task ( void )
{
    ecg4_process(  );
    if ( ecg4_responseReady( &ecg4 ) )
    {
        process_response( );
    }
}

void main ( void )
{
    application_init( );

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


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

Additional Support

Resources