TI’s TMS320C5515 DSP Medical Development Kit (Rev. B) supports the development of complete medical applications such as electrocardiogram (ECG), digital stethoscope and pulse oximeter. Typical applications include analog front ends (AFEs), signal processing algorithms, and user control and interaction. TMS320C5515 is a low-power fixed-point digital signal processor (DSP), using TMS320C55x™ DSP processor core, the core operating voltage is 1.05V/1.3V, and the I/O voltage is 1.8/2.5/2.75/3.3V. 16.67/13.33/10/8.33-ns instruction cycles, clock rates 60-, 75-, 100-, 120-MHz, with 320kB of on-chip RAM.

ECG design

The TMS320C5515 fixed-point digital signal processor is a member of TI’s TMS320C5000™ fixed-point digital signal processor (DSP) product family for low-power applications.

The fixed-point DSP is based on the TMS320C55x™ DSP series CPU processor core. The C55x™ DSP architecture achieves high performance and low power consumption by increasing parallelization and concentrating on power saving. The CPU supports an internal bus structure consisting of 1 program bus, 1 32-bit data readout bus, 2 16-bit data readout buses, 2 16-bit data write buses and other dedicated buses for peripherals and DMA activities. These buses provide the capability to perform four 16-bit data reads and two 16-bit data writes in a single cycle. The device also includes 4 DMA controllers, each with 4 channels, enabling data transfer in the context of 16 independent channels without CPU intervention. During or independent of CPU activity, each DMA controller can perform 1 32-bit data transfer per cycle.

The C55x CPU provides 2 multiply-accumulate (MAC) units, each of which can perform a 17-bit × 17-bit multiply and a 32-bit add in a single cycle. The central 40-bit arithmetic/logic unit (ALU) is supported by another 16-bit ALU. The use of the ALU is controlled by the instruction set, providing the ability to optimize parallel activity and power consumption. These resources are stored in the address unit (AU) and data unit (DU) of the C55x CPU.

Figure 1 TMS320C5515 block diagram

Figure 2 Medical Development Kit (MDK) hardware block diagram

The C55x CPU supports a variable byte width instruction set, which increases code density. The Instruction Unit (IU) fetches 32-bit programs from internal or external memory and queues the instructions against the Program Unit (PU). The program unit decodes instructions, directs tasks to address unit (AU) and data unit (DU) resources, and manages a fully protected pipeline. The early branch feature avoids pipeline emptying when conditional instructions are executed.

General purpose input and output functions and a 10-bit SAR ADC provide ample status, interrupt and bit I/O pins for LCD displays, keyboards and media interfaces. Via 2 Multimedia Card/Secure Digital (MMC/SD) peripherals, 4 Inter-IC Sound (I2S BusTM) modules, 1 Serial Port Interface (SPI) with 4 chip selects, 1 I2C Multi-Master- Serial media support is implemented from the slave interface and a Universal Asynchronous Receiver/Transmitter (UART) interface.

The device peripheral set includes an external memory interface (EMIF) for seamless access to asynchronous memory (such as EEPROM, NOR, NAND, and SRAM) and high-speed, high-density memory (such as synchronous DRAM (SDRAM) and mobile SDRAM (mSDRAM)) . Other peripherals include: High-speed Universal Serial Bus (USB2.0) Device-only mode and Real Time Clock (RTC). The device also includes three general-purpose timers (one of which can be configured as a watchdog timer) and an analog phase-locked loop (APLL) clock generator.

In addition, the device contains a tightly coupled FFT hardware accelerator. Tightly coupled FFT hardware accelerator supports 8-point to 1024-point (power of 2) real and complex FFTs. Also, the device contains 3 integrated LDOs (DSP_LDO, ANA_LDO and USB_LDO) that can power different parts of the device. DSP_LDO can provide 1.3V~1.05V voltage for DSP core (CVDD). To achieve the lowest power operation, the programmer can turn off the internal DSP_LDO while the external power supply is supplying the RTC (CDDRTC and DVDDRTC), thus reducing the power consumption of the DSP core (CVDD). ANA_LDO is designed to provide 1.3V for DSP PLL (VDDA_PLL), SAR and power management circuit (VDDA_ANA). USB_LDO provides 1.3V for USB core digital (USB_VDD1P3) and PHY circuit (USB_VDDA1P3). The RTC alarm interrupt or wake-up pin can restart the internal DSP_LDO to re-power the DSP core.

The device is supported by the industry’s award-winning eXpressDSP™, Code Composer Studio™ Integrated Development Environment (IDE), DSP/BIOS™, Texas Instruments algorithm standards and the industry’s largest third-party network. Code Composer Studio IDE features code generation tools including C compiler and linker, RTDXTM, XDS100TM, XDS510TM, XDS560™ emulated device drivers and evaluation modules. The device is also supported by the C55x DSP library with over 50 basic software cores (FIR filter, IIR filter, FFT and various math functions) and chip support libraries.

Figure 3 Outline drawing of ECG board

Figure 4 Outline drawing of ECG front end mounted on C5515 EVM

Main features of TMS320C5515

• High performance/low power C55xTM fixed-point DSP

• 16.67/13.33/10/8.33-ns instruction cycle time

• 60, 75, 100 and 120MHz clock rates

• 320kB on-chip RAM

• 16/8-bit External Memory Interface (EMIF)

• 2 Multimedia Cards/Secure Digital I/F

• Serial port I/F (SPI) with 4 chip selects

• 4 Inter-IC Sounds (I2S Bus™)

• USB 2.0 full-speed and high-speed devices

• LCD bridge with asynchronous interface

• Tightly coupled FFT hardware accelerator

• 10-bit 4-input SAR ADC

• Real Time Clock (RTC) with crystal input

• 4 core isolated power domains

• 4 I/O isolated power domains

• 3 integrated LDOs

• Available in industrial temperature devices

• 1.05V core voltage, 1.8/2.5/2.75/3.3VI/O voltage

• 1.3V core voltage, 1.8/2.5/2.75/3.3VI/O voltage

Medical Development Kit (MDK)

Numerous emerging medical applications, such as electrocardiography (ECG), digital stethoscopes, and pulse oximeters, require high DSP processing performance at very low power consumption. The TMS320C5515 digital signal processor (DSP) is ideal for this type of application. The C5515 is a member of TI’s C5000TM fixed-point DSP platform. In order to develop various medical applications with the C5515, Texas Instruments developed the MDK based on the C5515 DSP. Typical medical applications include:

• an analog front end including sensors for acquiring signals of interest from the body;

• Signal processing algorithms for signal conditioning, measurement and measurement analysis to determine health status;

• User control and interaction, including graphical Display of signal processing results and connectivity for remote patient monitoring.

The MDK design supports complete medical application development. It contains the following elements:

• Analog front-end board (FE board) dedicated to C5515 key target medical applications (ECG, digital stethoscope and pulse oximeter), using TI’s analog components for medical applications;

• C5515 DSP Evaluation Module (EVM) motherboard;

• Medical application software, including example demonstrations.

Figure 5 ECG front-end block diagram

Figure 6 DSP software architecture diagram

Introduction to MDK Hardware

An electrocardiogram (ECG/EKG) is a recording of the electrical activity of the heart and is used to check for heart disease. Electric waves can be measured by selectively placing electrodes (electrical contact points) on the skin.

Key Features of the Medical Development Kit ECG

Key features of the MDK ECG system:

• 12-lead ECG output with 10-electrode input;

• Defibrillator protection circuit;

• Diagnostic quality ECG with bandwidth of 0.05Hz~150Hz;

• Heart rate display;

• Continuous disconnection detection;

• Real-time display of 12-lead ECG waveforms on the EVM LCD screen, 1 lead can be selected at a time;

• Y-axis (amplitude) zoom option on the EVM LCD screen;

• Real-time display of 12-lead ECG waveform on PC, 3 leads can be selected at a time;

• In PC application, zoom function on X-axis (time) and Y-axis (amplitude);

• In PC application, freeze screen option;

• Record ECG data, offline view option of ECG data recorded on PC application;

The MDK ECG system consists of the following elements:

• C5515 EVM

• ECG front panel

• ECG cable

(1) C5515 EVM

The EVM comes with a full set of free on-board components for a variety of applications.

For details on the C5515 EVM, please refer to the Medical Development Kit provided with the EVM.

The main components and interfaces of the C5515 EVM used in the MDK ECG system include:

• TMS320C5515 with 100MHz operating frequency introduced by Texas Instrument;

• User Universal Serial Bus (USB) port provided by C5512;

• Inter-Integrated Circuit (I2C)/Serial Peripheral Interface (SPI) Electrically Erasable Programmable Read-Only Memory (EEPROM);

• External Memory Interface (EMIF), I2C, Universal Asynchronous Receiver/Transmitter (UART), SPI Interface;

• SAR;

• External IEEE Standard 1149.1-1990, IEEE Standard Test Access Port and Boundary Scan Architecture (JTAG) emulation interface;

• Embedded JTAG controller;

• Color LCD display;

• Keys (User Switches).

The EVM is powered by an external +5V supply or battery and is designed to work with TI’s Code Composer Studio™ integrated development environment (IDE). Code Composer Studio communicates with the EVM board through an external emulator or an on-board emulator.

(2) ECG front-end board

On the ECG front panel, the potentials picked up by the electrodes pass through a defibrillator protection (DP) circuit within the ECG front panel. The front-end board then splits out 8 of the 12 ECG leads to provide digital inputs for the DSP subsystem. The front-end board can be connected to the EVM board through the universal front-end connector. The front-end board is connected to and powered by the C5515 EVM board using the I2C and I2S interfaces through the universal front-end connector.

The 16-channel analog-to-digital converter (ADC) (ADS1258) on the front-end board can be configured for 500Hz sampling rate and 24-bit data resolution. The ADC is connected to the C5515 using SPI.

(3) ECG cable

The ECG cable consists of 4 limb electrodes and 6 thoracic electrodes. This cable is connected to the front panel via a DB15 connector. ECG electrodes capture ECG signals from ECG simulator/patient and send them to the ECG front-end board; off-the-shelf ECG cables are used.

Link to this article：TMS320C5515: Electrocardiogram (ECG) MDK Development Solution