导航:Digital Stethoscope Implementation on the TMS320VC5505 DSP Medical Development Kit (MDK)
The main elements of a Digital Stethoscope are the sensor unit that captures the heart and lung sounds (also known as auscultations), digitization, and digital processing of the auscultations for noise reduction, filtering and amplification. Algorithms for heart rate detection and heart defect detection may also be included.
Power and Battery Management are key in this ultra-portable diagnostic tool, where key design considerations are ultra-low power consumption and high efficiency driven by the need for extended battery life, and high precision with a fast response time allowing quick determination of the patient’s health status. Additional requirements may drive the need for recording the auscultations, cabled or wireless interfaces for transmission of the auscultations. Also, to enable ease of use, features like touch screen control and display backlighting are key to usability of the device. Adding all these features without significantly increasing power consumption is a huge challenge. Texas Instruments portfolio of Processors, Instrumentation and Buffer Amplifiers, Power and Battery Management, Audio Codecs, and both wired and wireless interface devices provides the ideal tool box for Digital Stethoscope applications.
The common core subsystems of a Digital Stethoscope are:
Analog Front-End/Sensor Interface and Codec
Auscultations signal input is amplified and then digitized by the Audio Codec. Auscultations signal after being digitized and subjected to signal processing, is converted to analog and sent to the stethoscope earpiece.
Low Power Processor
Processors capable of executing all of the digital stethoscopes signal processing including key functions such as noise reduction, algorithms for heart rate detection, and heart defect detection while maintaining a very low constant current draw from the battery are good fit. The ability to control interfacing with memory and peripheral devices is also helpful. Given the nature of the device, processors that can manage the digital display and keyed functions allowing auscultation waveforms to be displayed and manipulated without additional components are ideal.
Data Storage and Transmission
The auscultations can be recorded on MMC/SD card, or on a USB device. It can also be transmitted via wireless capability such as Bluetooth.
Digital Stethoscope Medical Development Kit
TIs TMS320VC5505 evaluation module together with TIs digital stethoscope analog front-end module make up the new C5505 DS Medical Development Kit (MDK) provides developers access to a development tool set that offers a complete signal chain solution along with software to save months of development time and for portable patient monitoring applications that demand battery efficiency.
图1. 数字听诊器方框图
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
图2.VC5505 EVM评估板外形图
图3.数字听诊器前端板外形图
图4.数字听诊器前端方框图
The front-end board contains the following stages:
Pre-amplifier
Low pass filter
AC coupling block
Audio codec
Front-end connector
Digital stethoscope analog front-end module can be used with C5505 EVM to make up the C5505 DS MDK that offers a complete signal chain solution along with software
图5.增益31的前置放大器
图6.一阶低通滤波器
图7. TLV320AIC3254方框图
图8. VC5505 DSP 和TLV320AIC3254间接口方框图
图9. 数字听诊器前端板电路图(1)
图10. 数字听诊器前端板电路图(2)
图11. 数字听诊器前端板电路图(3)
数字听诊器前端板材料清单(BOM):
