TI 公司的ECG解決方案是采用TMS320VC5505 定點(diǎn)DSP,它是基于TMS320C55x DSP CPU核的定點(diǎn)DSP,它的C55x? DSP架構(gòu)可得到高性能和低功耗特性,CPU支持內(nèi)部總線架構(gòu),包括一條可編程總線,一條321位數(shù)據(jù)總總線和兩條16位數(shù)據(jù)讀總線,兩條數(shù)據(jù)寫(xiě)總線和專門(mén)用于外設(shè)和DMA的其它總線. TMS320VC5505還包括4個(gè)DMA控制器,每個(gè)四路.時(shí)鐘為60MHz或100MHz,指令周期為16.67ns或10ns.主要用于無(wú)線音頻設(shè)備,回聲消除耳機(jī),手提媒體設(shè)備,視頻,工業(yè)控制,指紋生物學(xué)和SDR. 本文介紹了TMS320VC5505的主要特性和方框圖以及采用TMS320VC5505的ECG解決方案方框圖, ECG前端板詳細(xì)電路圖和所用材料清單(BOM).

Basic functions of an ECG machine include ECG waveform display, either through LCD screen or printed paper media, and heart rhythm indication as well as simple user interface through buttons. More features, such as patient record storage through convenient media, wireless/wired transfer and 2D/3D display on large LCD screen with touch screen capabilities, are required in more and more ECG products. Multiple levels of diagnostic capabilities are also assisting doctors and people without specific ECG trainings to understand ECG patterns and their indication of a certain heart condition. After the ECG signal is captured and digitized, it will be sent for display and analysis, which involves further signal processing.

圖1.TI ECG方框圖

ECG Implementation on the TMS320VC5505 DSP Medical Development Kit (Rev. A)

The TMS320VC5505 is a member of TIs TMS320C5000? fixed-point Digital Signal Processor (DSP) product family and is designed for low-power applications.

The TMS320VC5505 fixed-point DSP is based on the TMS320C55x? DSP generation CPU processor core. The C55x? DSP architecture achieves high performance and low power through increased parallelism and total focus on power savings. The CPU supports an internal bus structure that is composed of one program bus, one 32-bit data read bus and two 16-bit data read buses, two 16-bit data write buses, and additional buses dedicated to peripheral and DMA activity. These buses provide the ability to perform up to four 16-bit data reads and two 16-bit data writes in a single cycle. The TMS320VC5505 also includes four DMA controllers, each with 4 channels, providing data movements for 16-independent channel contexts without CPU intervention. Each DMA controller can perform one 32-bit data transfer per cycle, in parallel and independent of the CPU activity.

The C55x CPU provides two multiply-accumulate (MAC) units, each capable of 17-bit x 17-bit multiplication and a 32-bit add in a single cycle. A central 40-bit arithmetic/logic unit (ALU) is supported by an additional 16-bit ALU. Use of the ALUs is under instruction set control, providing the ability to optimize parallel activity and power consumption. These resources are managed in the Address Unit (AU) and Data Unit (DU) of the C55x CPU.

The C55x CPU supports a variable byte width instruction set for improved code density. The Instruction Unit (IU) performs 32-bit program fetches from internal or external memory and queues instructions for the Program Unit (PU). The Program Unit decodes the instructions, directs tasks to the Address Unit (AU) and Data Unit (DU) resources, and manages the fully protected pipeline. Predictive branching capability avoids pipeline flushes on execution of conditional instructions.

The general-purpose input and output functions along with the 10-bit SAR ADC provide sufficient pins for status, interrupts, and bit I/O for LCD displays, keyboards, and media interfaces. Serial media is supported through two MultiMedia Card/Secure Digital (MMC/SD) peripherals, four Inter-IC Sound (I2S Bus?) modules, one Serial-Port Interface (SPI) with up to 4 chip selects, one I2C multi-master and slave interface, and a Universal Asynchronous Receiver/Transmitter (UART) interface.

The VC5505 peripheral set includes an external memory interface (EMIF) that provides glueless access to asynchronous memories like EPROM, NOR, NAND, and SRAM. Additional peripherals include: a high-speed Universal Serial Bus (USB2.0) device mode only, and a real-time clock (RTC). The DMA controller provides data movement for sixteen independent channel contexts without CPU intervention, providing DMA throughput of up to two 16-bit words per cycle. This device also includesthree general-purpose timers with one configurable as a watchdog timer, and a analog phase-locked loop (APLL) clock generator.

In addition, the VC5505 includes a tightly-coupled FFT Hardware Accelerator. The tightly-coupled FFT Hardware Accelerator supports 8 to 1024-point (in power of 2) real and complex-valued FFTs.

TMS320VC5505主要特性:

High-Performance, Low-Power, TMS320C55x? Fixed-Point Digital Signal Processor

16.67-, 10-ns Instruction Cycle Time 60-, 100-MHz Clock Rate

One/Two Instruction(s) Executed per Cycle

Dual Multipliers [Up to 200 Million Multiply-Accumulates per Second (MMACS)]

Two Arithmetic/Logic Units (ALUs)

Three Internal Data/Operand Read Buses and Two Internal Data/Operand Write Buses

Fully Software-Compatible With C55x Devices

Industrial Temperature Devices Available

320K Bytes Zero-Wait State On-Chip RAM, Composed of:

64K Bytes of Dual-Access RAM (DARAM), 8 Blocks of 4K x 16-Bit

256K Bytes of Single-Access RAM (SARAM), 32 Blocks of 4K x 16-Bit

128K Bytes of Zero Wait-State On-Chip ROM (4 Blocks of 16K x 16-Bit)

16-/8-Bit External Memory Interface (EMIF) with Glueless Interface to:

8-/16-Bit NAND Flash, 1- and 4-Bit ECC

8-/16-Bit NOR Flash

Asynchronous Static RAM (SRAM)

Direct Memory Access (DMA) Controller Four DMA With 4 Channels Each (16-Channels Total)

Three 32-Bit General-Purpose Timers

One Selectable as a Watchdog and/or GP

Two MultiMedia Card/Secure Digital (MMC/SD) Interfaces

Universal Asynchronous Receiver/Transmitter (UART)

Serial-Port Interface (SPI) With Four Chip-Selects

Master/Slave Inter-Integrated Circuit (I2C Bus?)

Four Inter-IC Sound (I2S Bus?) for Data Transport

Device USB Port With Integrated 2.0 High-Speed PHY that Supports: USB 2.0 Full- and High-Speed Device

LCD Bridge With Asynchronous Interface

Tightly-Coupled FFT Hardware Accelerator

10-Bit 4-Input Successive Approximation (SAR) ADC

Real-Time Clock (RTC) With Crystal Input, With Separate Clock Domain, Separate Power Supply

Four Core Isolated Power Supply Domains: Analog, RTC, CPU and Peripherals, and USB

Four I/O Isolated Power Supply Domains: RTC I/O, EMIF I/O, USB PHY, and DVDDIO

Low-Power S/W Programmable Phase-Locked Loop (PLL) Clock Generator

On-Chip ROM Bootloader (RBL) to Boot From NAND Flash, NOR Flash, SPI EEPROM, or I2C EEPROM

IEEE-1149.1 (JTAG?) Boundary-Scan-Compatible

Up to 26 General-Purpose I/O (GPIO) Pins (Multiplexed With Other Device Functions)

196-Terminal Pb-Free Plastic BGA (Ball Grid Array) (ZCH Suffix)

1.05-V Core (60 MHz), 1.8-V, 2.5-V, 2.8-V, or 3.3-V I/Os

1.3-V Core (100 MHz), 1.8-V, 2.5-V, 2.8-V, or 3.3-V I/Os

TMS320VC5505應(yīng)用:

Wireless Audio Devices (e.g., Headsets, Microphones, Speakerphones, etc.)

Echo Cancellation Headphones

Portable Medical Devices

Voice Applications

Industrial Controls

Fingerprint Biometrics

Software Defined Radio

圖2.TMS320VC5505功能方框圖

A number of emerging medical applications such as electrocardiography (ECG), digital stethoscope, and pulse oximeters require DSP processing performance at very low power. The TMS320VC5505 digital signal processor (DSP) is ideally suited for such applications. The VC5505 is a member of TIs C5000? fixed-point DSP platform. To enable the development of a broad range of medical applications on the VC5505, Texas Instruments has developed an MDK based on the VC5505 DSP. A typical medical application includes:

An analog front end, including sensors to pick up signals of interest from the body

Signal processing algorithms for signal conditioning, performing measurements and running analytics on measurements to determine the health condition

User control and interaction, including graphical display of the signal processing results and connectivity to enable remote patient monitoring

The MDK is designed to support complete medical applications development. It includes the following elements:

Analog front-end boards (FE boards) specific to the key target medical applications of the VC5505 (ECG, digital stethoscope, pulse oximeter), highlighting the use of the TI analog components for medical applications

VC5505 DSP evaluation module (EVM) main board

Medical applications software including example demonstrations Several elements of the MDK pulse oximeter system are:

VC5505 EVM

Pulse oximeter front-end board

Finger probe sensor

The schematics for the ECG front-end board

圖3. ECG前端板電路圖(1)

圖4. ECG前端板電路圖(2): ECG電極:V1 V2 V3

圖5. ECG前端板電路圖(3):ECG電極:V4 V5 V6

圖6. ECG前端板電路圖(4):ADC部分

圖7. ECG前端板電路圖(5):ECG電極檢測(cè)

圖8. ECG前端板電路圖(6):右腿驅(qū)動(dòng)部分

圖9. ECG前端板電路圖(7):電源和接口部分

ECG前端板材料清單:

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