Intermediate
30 min
0

ECG at your fingertips with ADS1194 and PIC18LF46K80

Unveiling vital rhythms

ECG 2 Click with Curiosity HPC

Published Nov 01, 2023

Click board™

ECG 2 Click

Development board

Curiosity HPC

Compiler

NECTO Studio

MCU

PIC18LF46K80

Experience the power of real-time ECG monitoring that provides instant and accurate insights into heart health

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Hardware Overview

How does it work?

ECG 2 Click is based on the ADS1194, a low-power, 8-channel, 16-bit analog front-end for biopotential measurements from Texas Instruments. The ADS1194 is a multichannel simultaneous sampling delta-sigma analog-to-digital converter with a built-in programmable gain amplifier, internal reference, and onboard oscillator. It has a flexible input multiplexer per channel that can be independently connected to the internally generated signals for test, temperature, and lead-off detection. This ADC can sample data in a range of 125sps up to 8ksps data rates, with a programmable gain in 1, 2, 3, 4, 6, 8, or 12 steps. In addition, the ECG 2 Click features the built-in right leg drive amplifier, lead-off detection, WCT, test signals, pace detection channel selection, and more. The ECG 2 Click can work in several modes. The Continuous mode is ideal for applications that require a fixed stream of conversion results. The Single-Shot conversion mode is provided for applications that require a non-standard or non-continuous data rate. An onboard 3.5mm phone

jack is used to connect cables/electrodes to the Click board™. The electrode collects voltage from the skin, after which the signal is amplified, filtered, and sent to the host MCU over the mikroBUS™ socket. The three electrodes should be placed on the left arm, right arm, and the left side of the abdomen (below the heart), on the left leg. In addition to the phone jack, the ECG 2 Click includes screw terminals for a 4-wire measurement. ECG 2 click can also be connected by four electrodes placed on both arms and legs. The final measurement results can be displayed as an Electrocardiogram using a free app, the MikroPlot, a free data visualization tool (Windows). It's a simple tool to help you visualize sensor data recorded over time, suitable for biosignals (ECG, EEG, EMG) and environmental data logging (temperature, humidity, and more). The graph is generated from data sent from the MCU (ADC values from ECG 2 click input + timestamp). The app can receive data sets from a microcontroller through a USB UART connection. ECG 2 Click uses

a standard 4-Wire SPI serial interface to communicate with the host MCU. The data-ready output is used as a status signal to indicate when data are ready, where the DRD pin will go LOW if new data are available. In addition, other pins meet the ECG 2 Click's functionalities. The ADS1194 can be reset over the RST pin with an active LOW logic state, while it can be powered down with an active LOW on the PWD pin. The host MCU can be used to detect the presence of the pulse by bringing out the output of the PGA at the PAC pin (TEST PACE OUT1). This Click board™ can be operated only with a 3.3V logic voltage level while it uses a 5V for analog power supply via LDO (3V stabilized). 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 2 Click hardware overview 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 2 Click accessories image

Used MCU Pins

mikroBUS™ mapper

Test Pace Out
RA1
AN
Reset
RD0
RST
SPI Chip Select
RA3
CS
SPI Clock
RB1
SCK
SPI Data OUT
RB2
MISO
SPI Data IN
RB3
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Power Down
RC2
PWM
Data Ready
RB5
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

Schematic

ECG 2 Click Schematic schematic

Step by step

Project assembly

Curiosity HPC front image hardware assembly

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

Curiosity HPC front image hardware assembly
GNSS2 Click front image 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 2 Click driver.

Key functions:

  • ecg2_read_an_pin_value - ECG 2 read AN pin value function

  • ecg2_send_command - ECG 2 send command function

  • ecg2_read_channel_data - ECG 2 read data channel 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 main.c
 * @brief ECG2 Click example
 *
 * # Description
 * This is an example that demonstrates the use of the ECG 2 Click board.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes SPI and UART communication, configures INT pin as INPUT, RST pin as OUTPUT, CS pin as 
 * OUTPUT and PWM pin as OUTPUT. Initializes SPI driver, initializes ECG2 click, sends START and 
 * RDATAC opcodes.
 *
 * ## Application Task
 * Captures readings from channel and plots data to serial plotter.
 *
 * @author Stefan Ilic
 *
 */

#include "board.h"
#include "log.h"
#include "ecg2.h"

static ecg2_t ecg2;
static log_t logger;
uint32_t time;

void application_init ( void )
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    ecg2_cfg_t ecg2_cfg;  /**< Click config object. */

    /** 
     * 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.
    ecg2_cfg_setup( &ecg2_cfg );
    ECG2_MAP_MIKROBUS( ecg2_cfg, MIKROBUS_1 );
    if ( SPI_MASTER_ERROR == ecg2_init( &ecg2, &ecg2_cfg ) )
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    SET_SPI_DATA_SAMPLE_EDGE;
    
    if ( ECG2_ERROR == ecg2_default_cfg ( &ecg2 ) )
    {
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    }
    Delay_ms( 100 );
    ecg2_send_command( &ecg2, ECG2_START_CONVERSION );
    Delay_ms( 100 );
    ecg2_send_command( &ecg2, ECG2_ENABLE_READ_DATA_CONT_MODE );
    Delay_ms( 100 );
    
    log_info( &logger, " Application Task " );
    Delay_ms( 100 );
}

void application_task ( void ) 
{   
    uint16_t ecg_an = 0;
    ecg2_read_channel_data( &ecg2, 5, &ecg_an );
    log_printf( &logger, " %.6u, %.8lu \r\n", ecg_an, time );
    time += 5;
    Delay_ms( 5 );   
}

void main ( void )
{
    application_init( );

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

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

Additional Support

Resources