Electrocardiography (ECG) Reference Design Embedded Starter Kit

Publish Date: Jul 27, 2017 | 9 Ratings | 4.67 out of 5 | Print

Overview

The medical device community recognizes embedded technology as a valuable asset; however, embedded technology has become increasingly complex making it more challenging for non-technical experts to design full-featured medical device prototypes. Therefore, a new approach to design is needed. Graphical System Design is a revolutionary approach to solving design challenges that blends intuitive, graphical programming and flexible, commercial-off-the-shelf hardware, while still allowing for customization. Graphical System Design bridges the abilities of the embedded design expert with the domain expert, such as a medical device expert, to accelerate innovation. The Electrocardiography (ECG) Reference Design Embedded Starter Kit combines a Texas Instruments ECG module, a National Instruments Single Board RIO, and a LabVIEW application into a working ECG prototype. The prototype can operate as a stand-alone application or as a component within a higher level integrated system, which may include components such as motor control or high speed data acquisition.



Figure 1: The launch screen of the ECG Starter Kit Application Software.

Table of Contents

  1. Using the Electrocardiography ECG Reference Design Embedded Starter Kit
  2. HARDWARE COMPONENTS
  3. SOFTWARE COMPONENTS
  4. The Completed Prototype
  5. Source Code, Requirements Documents and Demonstration Examples
  6. Other Documents Related to the ECG Starter Kit Setup
  7. Disclamer
  8. Testing Your ECG (EKG) Products to ANSI/AAMI EC13

1. Using the Electrocardiography ECG Reference Design Embedded Starter Kit

The Electrocardiography ECG Reference Design Embedded Starter Kit incorporates algorithm engineering to build a real-world prototype.  Through graphical system design, LabVIEW is combined with an embedded device to accelerate development and release of a product.  Before developing the prototype, it may be useful to review how the heart works as well as the basics of ECG measurements, which are described in Bioelectromagnetism and the 12 Lead ECG System.

To build the complete embedded prototyping kit, the following components are required:

 

 Component  Notes
Hardware
Texas Instruments ECG Analog Front End reference design kit  Source: Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE)
NI Single Board RIO Embedded Evaluation kit The ECG Starter Kit uses the NI sbRIO-9631; the  NI Embedded Evaluation Kit includes a sbRIO and evaluation versions of LabVIEW, LabVIEW Real-Time module, and LabVIEW FPGA module.
Adapter to connect the NI sbRIO to the TI ECG Analog Front End board Custom designed and ordered; described in the NI sbRIO Adapter to the Texas Instruments Electrocardiogram (ECG) Analog Front End Module document.
12 lead ECG cable Standard, off-the-shelf 12 lead ECG cable
ECG simulator (optional) Used for testing and demonstration purposes.
Software
LabVIEW Real-Time Module *See the product page for LabVIEW Real-Time Module
LabVIEW FPGA Module *See the product page for LabVIEW FPGA Module
LabVIEW Digital Filter Design Toolkit See the product page for Digital Filter Design Toolkit
LabVIEW FPGA IP to control the TI ADS1258 16-Channel, 24-Bit ADC Tutorial and download of LabVIEW FPGA IP for Texas Instruments ADS1258 16-Channel, 24-Bit ADC
Electrocardiography ECG Starter Kit Application Software Tutorial and download of Electrocardiography ECG Starter Kit Application Software

*Note: Evaluation version included in the NI Embedded Evaluation Kit

 

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2. HARDWARE COMPONENTS

Aside from the ECG cable and optional simulator, the ECG Reference Design Embedded Starter Kit is composed of a Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE), a custom-designed adapter board, and a NI Single Board RIO-9631.

Figure 2: The embedded hardware that composes the ECG Reference Design Embedded Starter Kit is (1) the Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE), (2) the custom-designed adapter  board, and (3) NI Single Board RIO-9631.

Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE)

The Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE) module (Figure 3) reads 8 out of 12 ECG leads as analog signals and provides the digital output to the LabVIEW-based, processing subsystem of the FPGA and real-time processor.  The front-end board is interfaced with the NI sbRIO board through the custom adapter board connector.  The 16 channel analog-to-digital converter (ADC) (ADS1258) is configured for a 500Hz sampling rate per channel and has 24-bit data resolution. The sbRIO controls the ADC with SPI communication and has the ability to do I2C communication to implement lead-off detection.

Figure 3: Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE)

The ECG cable consists of ten leads, which are connected in the standard, 12-Lead ECG configuration with four limb leads and six chest leads. The other end of the cable is connected to the front-end board through the DB15 connector. The ECG electrodes pick up ECG signals from the ECG simulator or test subject and send them to the ECG front-end board. 

The Texas Instruments front-end board reference design can perform the following actions:

    • Right leg driving circuit
    • Lead-off detection
    • Derivation of eight ECG leads using instrumentation amplifiers
    • Low-pass filtering (anti-aliasing)
    • Analog-to-digital conversion (ADC)

For a complete description of the TI front-end board, review the ECG Implementation on the TMS320VC5505 DSP Medical Development Kit (MDK) user manual.   As stated in the user manual, operational amplifiers are used to create measurements for Lead I and Lead II, and the eight ECG leads are formed using the following relationships:

Lead I = Left Arm - Right Arm

Lead II = Left Leg - Right Arm

Lead V1 = V1 - (Left Arm + Right Arm + Left leg)/3

Lead V2 = V2 - (Left Arm + Right Arm + Left leg)/3

Lead V3 = V3 - (Left Arm + Right Arm + Left leg)/3

Lead V4 = V4 - (Left Arm + Right Arm + Left leg)/3

Lead V5 = V5 - (Left Arm + Right Arm + Left leg)/3

Lead V6 = V6 - (Left Arm + Right Arm + Left leg)/3

Lead III, Lead aVR, Lead aVL, and Lead aVF are calculated in software using Lead I and Lead II.  These calculations are discussed in more detail in the Electrocardiography (ECG) Starter Kit Application Software article. 

 

NI sbRIO Adapter to the Texas Instruments Electrocardiogram (ECG) Analog Front End Module

The NI sbRIO Adapter to the Texas Instruments Electrocardiogram (ECG) Analog Front End Module tutorial explains how to build an adapter printed circuit board (PCB) which directly connects the NI Single Board RIO (sbRIO) to the Texas Instruments TMDXMDKEK1258 Electrocardiogram (ECG) Analog Front End Module.

All design files are available for National Instruments' suite of design tools: NI Multisim capture and simulation, and NI Ultiboard layout and routing.  The complete gerbers can be downloaded, and the board design can be sent to a low-cost fabrication facility such as Sunstone Circuits.  

Figure 4: The 3D view of the NI sbRIO Adapter to the Texas Instruments Electrocardiogram (ECG) Analog Front End Module was created with NI Ultiboard.

 

NI Embedded Evaluation Kit

The NI Embedded Evaluation Kit (Figure 5) is the last hardware component to the Electrocardiography ECG Reference Design Embedded Starter Kit.  Included in this kit is everything needed to evaluate the NI LabVIEW Real-Time and LabVIEW FPGA programming experience used to develop embedded applications for NI reconfigurable I/O (RIO) hardware platforms such as CompactRIO, integrated RIO, NI Single-Board RIO, and R Series devices.  This kit includes a guided experience to show how to configure and program embedded LabVIEW applications for real-time microprocessors and field-programmable gate array (FPGA) devices.

To create the ECG Reference Design, connect the NI sbRIO-9631 to the adapter, which connects to the TI ECG Analog Front End.  Power and ethernet are the only other connections required to complete the hardware aspect of the ECG Reference Design. 

Figure 5: The NI Embedded Evaluation Kit includes a NI sbRIO and the evaluation version of needed LabVIEW modules.

 

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3. SOFTWARE COMPONENTS

The ECG Reference Design Starter Kit is built on LabVIEW and utilizes the power of graphical programming ranging from user interface design to FPGA development.  Specifically, LabVIEW's signal processing capabilities, LabVIEW FPGA IP, and LabVIEW Real-Time are leveraged for this application.

Using LabVIEW Graphical Programming and Algorithm Engineering to Understand ECG Signals

In many medical device designs, the electrocardiogram (ECG) is often a fundamental component of the end product. LabVIEW, with its signal processing capabilities, provides a robust and efficient environment for resolving ECG signal processing challenges (Figure 6). The detailed application note, LabVIEW for ECG Signal Processing, demonstrates how to use LabVIEW's powerful tools in denoising, analyzing, and extracting ECG signals easily and conveniently. LabVIEW tools can be also used in other biomedical signal processing applications such as Magnetic Resonance Imaging (MRI) and Electroencephalography (EEG).

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Figure 6: Extracting unwanted signals from ECG data using LabVIEW for ECG Signal Processing

Algorithm engineering can help you to better understand heart signals. One method to harness algorithm engineering is to use the power of the PC with high performance software tools like LabVIEW.  Using existing recorded data files allows designers and engineers to find repeatable characteristics.  NI delivers a LabVIEW tool, the NI Biomedical Startup Kit, which is a suite of applications for use in the biomedical teaching field.  Biomedical startup kit examples enable you to apply biomedical solutions using National Instruments software, such as LabVIEW, with National Instruments PC based hardware.  Other areas to learn more about biomedical applications that use LabVIEW for algorithm engineering is to visit the Biomedical User Group Forums.

 

LabVIEW FPGA IP for Texas Instruments ADS1258 16-Channel, 24-Bit ADC

The document LabVIEW FPGA IP for Texas Instruments ADS1258 16-Channel, 24-Bit ADC explains how to control the TI ADS1258, a 16-Channel 24-Bit Analog-to-Digital (ADC) converter, using the SPI protocol from the NI sbRIO FPGA. This example demonstrates the ADS1258 LabVIEW FPGA SPI-based driver IP. and shows how to use the driver.  Figure 7 displays the pin assignments between the ADS1258 and the adapter.

Figure 7: sbRIO Adapter and pin-out of the LabVIEW FPGA IP for Texas Instruments ADS1258 16-Channel, 24-Bit ADC 

 

Electrocardiography ECG Starter Kit Application Software

Using the LabVIEW FPGA IP for the Texas Instruments ADS1258, a high-level LabVIEW based application called the Electrocardiography ECG Starter Kit Application Software (Figure 8) demonstrates a complete 12 Lead ECG system.

Figure 8: The software components that make up the Electrocardiography ECG Starter Kit Application Software are hosted on the sbRIO, the network, and a PC.

 

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4. The Completed Prototype

Designers require a solution such as an evaluation board to prototype their systems. However, these boards often do not include all the signal chain components needed for an application, as well as rarely include vision, motion, or ability to synchronize I/O. Additionally, designers often have to waste time developing custom boards for sensors or specialized I/O, just to complete a proof of concept.  Using flexible commercial off-the-shelf (COTS) prototyping platforms from National Instruments and Texas Instruments can truly streamline design, and eliminate much of the work required for hardware verification and board design.  Figure 9 shows our complete solution to ECG measurement analysis and embedded control.  The ECG simulator used is a product from HE Instruments.

Figure 9: Electrocardiography ECG Reference Design Embedded Starter Kit

With the many designs that are late or never released to market, or worse, designs failing after release, something needs to be done to get more high-quality products to market sooner. One way to address both of those issues is to prototype the systems by integrating real world signals and real hardware into the design process sooner so that high-quality designs are iterated upon and problems are found (and fixed) earlier.

If you are creating custom hardware for final deployment, it is difficult to have the software and hardware developed in parallel, as the software is never tested on representative hardware until the process reaches the system integration step. Additionally, you do not want the software development to be purely theoretical, because waiting until the system integration test to include I/O and test the design with real signals may mean that you discover problems too late to meet design deadlines.  

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5. Source Code, Requirements Documents and Demonstration Examples

See attachments for the complete source under LabVIEW 2010.

 

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6. Other Documents Related to the ECG Starter Kit Setup

Refer to the following documents to learn more about ECG measurements and the application of Graphical System Design using the NI sbRIO with the TI MDXMDKEK1258 Electrocardiogram (ECG) Analog Front End (AFE) module:

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7. Disclamer

Not for Diagnostic Use: For Feasibility Evaluation Only in Laboratory and Development Environments.

    • The adapter along with the NI SBRIO and TI Analog EVM front end must not be used for diagnostic purposes.
    • The adapter along with the NI SBRIO and TI Analog EVM front must not be used with other equipment that produces high voltages
    • This adapter along with the NI SBRIO and TI Analog EVM front are intended solely for evaluation and development purposes. They are not intended for use and may not be used as all or part of an end equipment product.
    • This adapter along with the NI SBRIO and TI Analog EVM front should be used solely by qualified engineers and technicians who are familiar with the risks associated with handling electrical and mechanical components, systems and subsystems.
    • Use only the proper power supplies for the adapter along with the NI SBRIO and TI Analog EVM front module.

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8. Testing Your ECG (EKG) Products to ANSI/AAMI EC13

Learn how to test and validate any Electrocardiography (ECG) (EKG)  based medical device to ANSI/AAMI EC13.  

In this document, you will learn how to automate and reduce time required to test and validate any ECG based device using NI PXI modular instruments and NI software.

Originally Authored By: Greg Crouch, National Instruments

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