Microprocessor based Design
for Biomedical Applications
MBE 3 – MDBA
I : Introduction
Today:
● Course Introduction and Administrative Information
● Survey of Student Skills
● Microcontrollers in Biomed Applications – Overview
● AVR Family Overview
● Outlook : The OpenEEG Project
● Start to assemble the Eval Boards ?
Semester Schedule:
In September, we will meet
● on Mondays ( 16:10 – 18:35 )
Monday, Sept. 24th we will start later, at 16:55 !
● on Thursdays ( 16:10 – 19:20 )
From October on, we will meet
● on Thursdays ( 16:10 – 19:20 )
Thursday, Nov. 1st there will be no lecture !
Room EDA B3.12
!! Check for updates of the Semesterplan on the CIS !!
Modes of evaluation:
● 40 % Project participation, Project reviews,
solved programming tasks
● 30 % Review of a scientific paper
Paper selection, workout and presentation
Presentations will be on Nov. 22th and Nov. 29th
● 30 % Examination at the end of the term
Theoretical Questions about the course topics
( without PC‘s or other material )
Programming task on paper, PC‘s allowed
Exam will be on Dec., 12 th
Our goals for this term:
● Practical usage of Microcontrollers in the Biomedical Context
● Understanding, usage and modification of a biosignal
(EEG-) acquisition system
● See examples of ongoing research in BME
● Implementation of project ideas
Course Topics
● Features of our hardware platform
● Firmware programming, solving programming tasks
● Data transfer and transmission Protocols
● Measurement of bioelectric signals and events
● Signal processing software and methods
● Biofeedback, Brain Computer Interfaces
● Standards for design and certification
● Design examples
http://people.brandeis.edu/~sekuler/eegERP.html
heavens sake!
... our EEG will have just 2 Channels …
Course Material
HARDWARE :
● Atmel AVR microcontrollers
● Evaluation Boards with ATmega8 microcontroller
● OpenEEG hardware (MonolithEEG)
● Electrodes and Sensors
● Hardware extensions for projects
Course Material
SOFTWARE :
● WinAVR Toolchain, AVR Studio DIE
● Programming tools, Bootloader
● PCB – Editor and Circuit Simulator
● Signal processing tools and Biosignal Software
The main hardware and software for our course are GPL‘d:
● GNU – The free software foundation
● GPL – GNU General Public License
● free sources, mention the authors !
Richard Stallman http://www.stallman.org
Draft of a timeline
First 2 - 3 weeks:
● Prepare the Evaluation Boards and cabling
● Getting started with the IDE
● Gain some knowledge about AVR features and
firmware programming
until October:
● Solve programming tasks
● Data Transmission, A/D conversion,
● Interrupt handling
Draft of a timeline
October - November:
● Understand the openEEG hardware
● Switch to the Monolith-EEG amplifier
● work with and modify the system firmware
from Novemeber :
● use our knowledge in a practical project
● review research papers, prepare a presentation
● project reviews, debugging, final examination
Survey of your skills
Query the given skills
.. to find out synergies and to adapt our timeline
(0) Finished Bachelor for Biomedical Engineering ?
(1) Concepts and usage of microcontrollers ?
(2) AVR microcontrollers + Tools ?
(3) Breadboard – circuits, Soldering, SMD ?
(4) Analog electronics ( OpAmps, Filtering ) ?
(5) Sampling and A/D Conversion ?
Query the given skills
(6) C-Programming, GCC-Toolchain ?
(7) Event-based firmware programming, interrupts ?
(8) Data Transmission using UART/RS232 ?
(9) Interfacing uC-firmware and PC (host-) software ?
(10) Design of PCBs using a CAD-Tool ?
(11) Usage of the Eagle-CAD Layout Editor ?
Query the given skills
(12) Soldering and building up electronic circuits
(13) Reading datasheets, studying new parts
(14) Physiological basics of bioelectricity
(15) Measurement of bioelectric events
(16) Signal processing with Matlab / Filters
What are your ideas / expectations for this course ?
Microcontrollers in embedded
biomedical Applications
Microcontrollers in embedded biomedical Applications:
We want to have systems that :
● are reliable
● are small and lightweight
● have a low power consumption
These issues are critical when we deal with body implants
I: Introduction
– Microcontrollers
Some features / advantages of microcontrollers:
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they are small and flexible
easy to use ( most of the time .. )
few external components and wires needed
low and ultra low power designs possible (-> PSoC, ASIC )
wide range of different uCs available
(memory, I/O, speed, busses, A/Ds )
● data interchange using standard bus systems;
-> various peripheral hardware accessible
● IDEs and toolchains for firmware programming /
● Simulation and high level languages
-> 90% of the manufactured CPUs are not found in desktop PCs but
in embedded systems, with growing areas of application: RFID,
hidden "ubiquitous" computing, wearables, "smart environments",
MEMS (micro electro-mechanical systems)
I: Introduction
– Microcontrollers
Some examples for uC-based biomed devices / applications:
● various sensors or meters:
Body temperature, Blood Pressure,
Blood Sugar Level, …
● Implants and prostetics
● Pacer makers (for heart, breathing, ...)
Adam blood glucose meter
● functional Electrostimulation
● Orthesis and artificial limbs
● Biosignal acquisition equipment
www.heartratemonitor.co.uk
I: Introduction
– Microcontrollers
Some examples for uC-based biomed devices / applications:
● portable emergency equipment (defibrillator, ..)
● Sports medicine
● Patient monitoring
● “Smart Homes", service robotics
● support of Communication for disabled persons
Life-point defibrillator
Spo2 Module
● wireless sensor networks / Body Area Network (BAN)
● Sensors and Actuators for stationary medical equipment
In a medical Context:
Dependability and Fault Tolerance are major issues.
● Failsafe: safe state after failure
● Fault recovery: normal operation can be restored
● Gracefully Degradation:
system continues (restricted) work
MTBF Mean Time Between Failure
Environment conditions / Materials
Redundant Hardware / Software makes sense here !
System Design and Integration:
● Hardware Selection for Development / Production
● Hardware and Software Co - Development
● System Modelling and Simulation, UML
The earlier a design bug is found, the better !
I: Introduction
– The Atmel AVR family of microcontrollers
AVR microcontrollers
I: Introduction
– The Atmel AVR family of microcontrollers
Why will we use an 8-bit AVR microcontroller in our course ?
● sufficient for many biomedical applications
● AVR Mega 8 features built-in A/D converters
● Fast and cheap ( < 3 € per unit )
● needs less power than more sophisticated uCs
● good support on the development side:
AVR-GCC (WinAVR Toolchain), AVR Studio
● widely used in OpenSource projects,
huge knowledge base and reference designs
● OpenEEG project is based on AVRs
I: Introduction
– The Atmel AVR family of microcontrollers
Members of the AVR family, different packages: 90s, Mega- and Tiny variants
http://superpositioned.com/articles/tag/exclusive
I: Introduction
– The Atmel AVR family of microcontrollers
AVR Product Families
● tinyAVR
General purpose Microcontroller with up to 4K Bytes
Flash program memory 128 Bytes SRAM and EEPROM.
● megaAVR
Self programming memory enables remote
reprogramming without additional circuitry.
Up to 256K Bytes Flash, 4K Bytes EEPROM and SRAM.
● LCD AVR
Integrated LCD driver, contrast control.
power consumption at 32 kHz < 20 μA.
● CAN AVR
Integrated CAN Controller
I: Introduction
– The Atmel AVR family of microcontrollers
AVR general features:
● RISC: most instructions need a single clock cycle
● Special Function Registers to access the built in
peripherals
● Low power and sleep modes
● In-system- programmable Flash memory
MegaAVR features:
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Self programming options
Operating voltages from 1.8-volt to 5.5-volt
10-bit A/D converter with channel multiplexer
USART, SPI and TWI (I2C) – Interfaces
JTAG in >16KB megaAVRs
I: Introduction
– The Atmel AVR family of microcontrollers
Programming the AVR
I: Introduction
– The Atmel AVR family of microcontrollers
Programming the AVR
1.) Write source code in assembler or higher language
Text editor, IDE
2.) Compile, Link (and locate) executable file
WinAVR GCC, Make, IDE
3.) Use hardware link and programmer software
to download firmware image to uC
I: Introduction
– The Atmel AVR family of microcontrollers
AVR programming options:
Firmware security:
locking via fuse-bits
Atmel AVR Quick Reference Guide http://www.atmel.com
I: Introduction
– The Atmel AVR family of microcontrollers
ISP: In system programming
● native Serial Peripheral Interface (SPI)
10-pin Kanda Dongle
(STK200)
6-pin Atmel
connector
http://www.mikrocontroller.net/articles/AVR_In_System_Programmer
I: Introduction
– The Atmel AVR family of microcontrollers
The AVR Studio IDE:
Atmel AVR Quick Reference Guide http://www.atmel.com
I: Introduction
– The Atmel AVR family of microcontrollers
AVR STK500 Evaluation Board
Firmware download via RS232,
using the STK500v2 protocol.
The STK500 hardware platform
transforms the RS232
commands to SPI commands
Supported by all AVRs
On-Board Leds, Keys, Cables
http://shop.mikrocontroller.net
I: Introduction
– The Atmel AVR family of microcontrollers
AVR ISP : In-System Programmer
http://www.btnode.ethz.ch
The ISP- Programmer:
An Adapter between PC /
RS232 and the on-chip SPI
programming interface
http://www.raphnet.net/divers/avrprog/avrisp.jpg
I: Introduction
– The Atmel AVR family of microcontrollers
AVR ISP mkII : In-System Programmer, USB-Version
The ISP mkII - Programmer:
An Adapter between PC / USB
and the on-chip SPI
programming interface
http://lintel.ls0578.net/Article
I: Introduction
– The Atmel AVR family of microcontrollers
Lots of ISP Clones: cheap remakes of the AVR ISP
http://www.restek.dk/grafik/ispclone.jpg
http://hubbard.engr.scu.edu/embedded/avr/boards
http://avrtools.co.kr
I: Introduction
– The Atmel AVR family of microcontrollers
AVR Dragon Board
Atmel's new low-cost generic programmer + debugger
JTAG, DebugWire, ISP, USB. 53x105mm, price less than $100
http://www.bfrdesign.com/blog.htm
I: Introduction
– The Atmel AVR family of microcontrollers
JTAG ICE / JTAG ICE mkII:
Atmel AVR Quick Reference Guide http://www.atmel.com
I: Introduction
– The Atmel AVR family of microcontrollers
ICE50 Emulator:
Atmel AVR Quick Reference Guide http://www.atmel.com
I: Introduction
– The Atmel AVR family of microcontrollers
AVR Application Notes regarding programming:
AVR910 (PDF) "Low-cost" In-system programming (AVRISP)
AVR911 (PDF) Open source serial programmer (AVROSP)
AVR109 (PDF) Self-Programming with a Bootloader
http://www.atmel.com/dyn/products/app_notes.asp?family_id=607
I: Introduction
– The Atmel AVR family of microcontrollers
The most simple and cheap solution for AVR firmware programming:
Parallel Port Cable + ISP Sofware
I: Introduction
– The Atmel AVR family of microcontrollers
Our Evaluation platform - the Pollin EvalBoard2 :
Features: ISP / JTAG connectors, RS232 level converter, 2 Leds, 3
Buttons, buzzer, 40Pin extension header. Price: 14.99 €
I: Introduction
– The Atmel AVR family of microcontrollers
EvalBoard2 top view:
Sockets for Attiny2313/21/15, Atmega8/16/32/8535
I: Introduction
– The Atmel AVR family of microcontrollers
EvalBoard2 jumper settings
I: Introduction
– Outlook: The OpenEEG Project
Outlook: the OpenEEG project
● Online since 1999
● Project aims:
development of a lost cost, high quality EEG amplifier
development of Open Source firmware / PC-software
sharing of knowledge the area of EEG / biosignal instrumentation and application
● Major Hardware Designs :
ModularEEG (6 Chn, non-SMD, Kit)
MonolithEEG (2 Chn, SMD, USB)
SoundcardEEG (FM/AM - Modulation
I: Introduction
– Outlook: The OpenEEG Project
Outlook: the OpenEEG project
● Available Software:
different firmware implementations
PC host software in JAVA, C++
Client/Server architecture for biosignal sharing
Software for filter design and application
Experimental BCI-software
● Hardware overview ModularEEG:
AVR-Atmega8 Microcontroller
Resolution: 10bit / 0.5 uV
Samplingrate: 1kHz
up to 6 Channels
DRL (driven right leg) – circuit
CMRR < -94dB
ModularEEG, digital + analog boards.
Author: Jörg Hansmann, http://openeeg.sf.net
I: Introduction
– Outlook: The OpenEEG Project
Outlook: Monolith EEG
● Small and leightweight SMD
● USB-powered
● one double-sided board with
extension plug
MonolithEEG amplifier. Author: Reiner Münch, http://openeeg.sf.net
I: Introduction
– Outlook: The OpenEEG Project
Outlook: BrainBay
● Windows software for Biosignal Processing and Biofeedback
● Real time graphical configuration of designs using
Input-, Processing- and Output-Elements
BrainBay OpenSource software. Author: Chris Veigl, http://brainbay.lo-res.org
I: Introduction
– Outlook: The OpenEEG Project
Preparation of Cables
Eval Boards
and Extension Boards
I: Introduction
– Hardware Preparation
I: Introduction
– Hardware Preparation
MonolithEEG
Extension Board
16 Pin Monolith Extension Header
16 Signals1:1 wired to a prototyping
connector;
Signals GND, MISO, MOSI, /RESET, SCK
additionally routed to the 10 Pin AVRISP Connector for firmware programming
4 Buttons with pulldown resistors (->GND)
8 Leds + Led-Driver IC
Led Anodes connected to Outputs (B0-B7) of
74HC245 – BusDriver-IC (Dir=VCC, /OE=GND)
Led-Cathodes connected to Resistor Net
(Resistor Net GND = Pin 1)
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Microprocessor based Design for Biomedical Applications