Microprocessor based Design for Biomedical Applications
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Microprocessor based Design for Biomedical Applications MBE 3 – MDBA XI : Project Outlooks. Resumee of our Project Works (1) We built 4 AVR Evaluation Board Kits and used them for basic firmware projects with the ATmega8 : ● AVR-GCC, make, AVRStudio toolchains

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Resumee of our Project Works (1)

We built 4 AVR Evaluation Board Kits and used

them for basic firmware projects with the ATmega8 :

●AVR-GCC, make, AVRStudio toolchains

● Firmware download via direct SPI access

● GPIO, Timer Interrupts, ISRs

● UART, Interrupt driven communication

● Analog/Digital Conversion

● Transfer of multiple channels, data packets

Resumee of our Project Works (2)

We brought up 4 Monolith-EEGs :

●soldered and debugged the SMD-boards

● soldered the extension boards with SPI connectors

● understood the analog and digtial schematics (nearly ;-)

● ported the firmware to the ATmega168

● used the FTDI UART-USB converter ICs

● investigated the bootloader-mechansim

● evaluated our designs with realtime EEG / ECG recordings

So I would say :

We did a great job !


For sure, this project could be extended.

Here come a few ideas ….

Possible Hardware extensions :

● an EEPROMto store configuration data

● battery driven (offline) operation:

what batteries / accus ? Stepup converter ?

● wireless communication: add a bluetooth or zigbee module


● on-board data-logging: interface with a MMD / SD memory card


● new sensors: GSR/EDA , temperature, pulse, acceleration ..


● evaluate active (dry) electrodes and alternative electrode caps


The Serial Peripheral Interface

Miso: master in slave out

Mosi: master out slave in

SCK: clock

SS: slave select

TWI – The Two Wire Interface (IIC Bus)

SDA : serial Data

SCL : serial Clock

R1, R2 : Pullup Resistors on the Bus lines, devices tri-state their outputs

line level goes low if any of the connected device outputs 0

START: SDA goes low during SCL high

STOP: SDA goes high during SCL high

TWI – The Two Wire Interface (IIC Bus)

●only two Bus Lines needed for bidirectional communication

● Master and Slave Operation

●Device can Operate as Transmitter or Receiver

●7-bit Address Space Allows up to 128 Different Slave Addresses

●Multi-master Arbitration Support

●Up to 400 kHz Data Transfer Speed

●Noise Suppression Circuitry Rejects Spikes on Bus Lines

●Wake-up when AVR is in sleep mode and slave address detected

as ever: the AVR datasheet has the details …

TWI – example: EEPROM interface to AVR


Possible Software extensions

at the uC (firmware) side:

● on-board filtering ( configure FIR / IIR filters for channels )


● on-board feature extraction ( pulse rate ? )

● Bidirectional communication :

change baud- and sampling rate at runtime

select relevant channels

allow access to I/O-pins ( Events ? ERP-recording ? )

error detection / correction for data transfer

… some of these features are already present in the p21-firmware:


Possible Software extensions

at the PC (host) side:

● write our own data packet parser

● write a simple biosignal tracing and recording software in a

platform independent environment

(JAVA? C++ & GTK / QT / SDL ?)

● investigate algorithms for feature extraction

(pattern recognition ? LDA / AR-Filter for SSVEP or μ -BCI ?)

BrainBay - extensions


● design Biosignal protocols with midi / optical feedback

Alpha / Theta Training ? REM-Detection ?

Muscle Rehabilitation Training ?

Extend / improve the software:

● add new modules

● remove OS-dependent parts

● improve signal handling …



● This project has lots of potential for future improvements

● in the optimal case, Open Source Projects are a win-win situation

I hope you enjoyed the show -

have a good time and much Alpha-Activity !