Seismic Octave Seismic Octave Programming for Programming for

Analog/Digital Analog/Digital ConvertersConverters

Michael W. SiekmanMichael W. SiekmanElectrical and Computer Electrical and Computer EngineeringEngineeringSenior Capstone Design Project Senior Capstone Design Project 20072007Advisor: James HedrickAdvisor: James Hedrick

The ProjectThe Project

Investigate Investigate analog/digital data analog/digital data acquisition (A/D acquisition (A/D DAQ) in the open DAQ) in the open source software source software environmentenvironment

Acquire and display Acquire and display analog inputanalog input

Implement as a Implement as a simple seismographsimple seismograph

Block DiagramBlock Diagram

Computer and Software

Seismic Activity(Input)

Display (Output)

SeismometerSignal

ConditioningA/D Converter

(PCI)

A/D Drivers

Octave Function

The SetupThe Setup

Analog to Digital Analog to Digital Conversion (A/D)Conversion (A/D) ManipulationManipulation DisplayDisplay Necessary in Necessary in

everyday everyday engineering life!engineering life!

Used extensively in Used extensively in PCsPCs

Variety of on-board Variety of on-board card optionscard options

The ProblemThe Problem

MATLAB MATLAB Numerical Numerical

Computing and Computing and ProgrammingProgramming

Powerful Powerful Engineering and Engineering and A/D processing toolA/D processing tool

$$$$$$

The SolutionThe Solution

GNU OctaveGNU Octave Open Source (GNU Open Source (GNU

Project)Project) Uses Linux OS Uses Linux OS

(FC5)(FC5) Same method, Same method,

different packagedifferent package Shell, DIYShell, DIY GNU Supporters GNU Supporters

around the worldaround the world

The PlanThe Plan A/D ConverterA/D Converter

Measurement Measurement Computing PCI-Computing PCI-DAS6035DAS6035

PCI card with Input PCI card with Input BoardBoard

16-bit resolution16-bit resolution Sampling rate of Sampling rate of

200kS/s (200kHz)200kS/s (200kHz) Selectable input Selectable input

voltage range of +/- voltage range of +/- 10V, 5V, 500mV, or 10V, 5V, 500mV, or 50mV50mV

The PlanThe Plan

SeismometerSeismometer PMD Scientific PMD Scientific

PMD103mPMD103m Receives seismic activityReceives seismic activity Output voltage represents Output voltage represents

forceforce Output connected to A/D Output connected to A/D

converterconverter Signal ConditioningSignal Conditioning

Between voltage output Between voltage output to A/D input boardto A/D input board

Terminal boardTerminal board

The PlanThe Plan

Output Output SpecificationsSpecifications 3D output (X,Y,Z)3D output (X,Y,Z) Output voltage swingOutput voltage swing

+/- 10V Single Ended+/- 10V Single Ended +/- 20V differential+/- 20V differential

+/- 5V is typical+/- 5V is typical

Bandwidth range is Bandwidth range is 0.033 – 50 Hz0.033 – 50 Hz

Sampling rate of A/D Sampling rate of A/D allows this w/o aliasingallows this w/o aliasing

Require 9-13V Power Require 9-13V Power

The PlanThe Plan

Seismometer to A/D BoardSeismometer to A/D Board Output of seismometer will not reach Output of seismometer will not reach

+/- 10V swing+/- 10V swing FFss = 2F = 2Fmaxmax

FFss > 2 (50Hz) > 2 (50Hz) FFss > 100 Hz > 100 Hz

16-bit resolution is more than enough16-bit resolution is more than enough 12V power source for Seismometer12V power source for Seismometer

The PlanThe Plan Comedi (Comedi (COCOntrol and ntrol and

MEMEasurement asurement IInterface)nterface) DAQ drivers for LinuxDAQ drivers for Linux Needed to modify in Needed to modify in

order to compile order to compile correctlycorrectly

Previous work in FC3Previous work in FC3 Fedora Core 5Fedora Core 5

Redhat Project variantRedhat Project variant Custom kernel filesCustom kernel files WorkaroundsWorkarounds

The PlanThe Plan Within Octave:Within Octave:

Programming similar to Programming similar to MATLABMATLAB

Develop functions or Develop functions or programsprograms

Interface with A/D Interface with A/D driversdrivers

Done outside of OctaveDone outside of Octave Receive A/D signalReceive A/D signal

Receive 100 samples Receive 100 samples from signalfrom signal

Process A/D signalProcess A/D signal Read voltagesRead voltages

DisplayDisplay Seismometer data plots Seismometer data plots

as seismographas seismograph

The ImplementationThe Implementation

System System ComponentsComponents Hardware Hardware

SeismometerSeismometer Terminal BoardTerminal Board Input BoardInput Board A/D ConverterA/D Converter

SoftwareSoftware A/D Converter A/D Converter

DriversDrivers DAQ Program DAQ Program Octave ProgramOctave Program

The ImplementationThe Implementation HardwareHardware

Layout of seismometer Layout of seismometer outputoutput

Connect to terminal Connect to terminal board including powerboard including power

+/- X value into input +/- X value into input boardboard

A/D ConverterA/D Converter 200 kHz sampling rate 200 kHz sampling rate

covers seismometer covers seismometer bandwidth (50 Hz max), bandwidth (50 Hz max), using 1 kHzusing 1 kHz

+/- 10V selected in +/- 10V selected in differential modedifferential mode

The ImplementationThe Implementation SoftwareSoftware

Linux preparationLinux preparation Problems with kernel source and headers being Problems with kernel source and headers being

correctcorrect Comedi InstallationComedi Installation

Compiled and installed Comedi drivers/libraryCompiled and installed Comedi drivers/library Modification of Comedi configuration and driversModification of Comedi configuration and drivers Insertion/configuration of driver (cb_pcidas64) into Insertion/configuration of driver (cb_pcidas64) into

kernelkernel DAQ programDAQ program

printdataprintdata Written in C with C and Comedi librariesWritten in C with C and Comedi libraries Accesses driver, retrieves a signal and samples it (100 Accesses driver, retrieves a signal and samples it (100

samples), and prints voltages to screensamples), and prints voltages to screen

The ImplementationThe Implementation

Software (cont)Software (cont) Octave program Octave program getwave.mgetwave.m

Accesses Accesses printdataprintdata outputoutput

Data is then Data is then formattedformatted

DisplayedDisplayed Replicates a static Replicates a static

sample of sample of seismographseismograph

The ResultsThe Results ResultsResults

Kernel was configured properly for ComediKernel was configured properly for Comedi Comedi application and libraries successfully Comedi application and libraries successfully

installed to be compatible with FC5installed to be compatible with FC5 A/D converter driver successfully inserted as A/D converter driver successfully inserted as

module into kernelmodule into kernel Testing drivers and Testing drivers and printdataprintdata DAQ program DAQ program

C battery input reads properly as DC at around 1.5vC battery input reads properly as DC at around 1.5v Function generator input reads as proper wave Function generator input reads as proper wave

(tested at both arbitrary sine and square wave)(tested at both arbitrary sine and square wave) printdataprintdata receives a signal from the receives a signal from the

seismometer and prints it properlyseismometer and prints it properly

The ResultsThe Results

Testing Octave program Testing Octave program getwave.mgetwave.m Properly receives data from Properly receives data from printdataprintdata

and displays its output data correctlyand displays its output data correctly 1.5V C battery shows as DC signal at @ 1.5v1.5V C battery shows as DC signal at @ 1.5v Function generator can show proper sine Function generator can show proper sine

wave and square wavewave and square wave Seismometer input is displayedSeismometer input is displayed

The ResultsThe Results

Still to be doneStill to be done Extend period over which 100 samples are taken, Extend period over which 100 samples are taken,

lower the sampling ratelower the sampling rate Need to verify that seismic action is being Need to verify that seismic action is being

properly read by DAQ software and Octaveproperly read by DAQ software and Octave Try dynamically linking Try dynamically linking printdataprintdata program to program to

OctaveOctave Requires translating to C++ and inclusion of Octave Requires translating to C++ and inclusion of Octave

library codelibrary code System can support DLSystem can support DL

User’s ManualUser’s Manual So others don’t have to go through the things that I didSo others don’t have to go through the things that I did

The FutureThe Future

Future work that can be done:Future work that can be done: Read all planes of seismometer outputRead all planes of seismometer output Dynamically linking DAQ program to Dynamically linking DAQ program to

OctaveOctave Creating a continuous stream of seismic Creating a continuous stream of seismic

data from the A/D board and displaying data from the A/D board and displaying it as a real time seismograph it as a real time seismograph Use Comedi functions to provide streaming Use Comedi functions to provide streaming

analog inputanalog input

The PayoffThe Payoff

Multiple Multiple applicationsapplications

Modular functions Modular functions and programsand programs

Access to powerful Access to powerful A/D tools without A/D tools without the heavy pricethe heavy price

Acknowledgments:Acknowledgments:

James HedrickJames Hedrick

Lance SpallholzLance Spallholz

Emad AndarawisEmad Andarawis

Everyone on the Comedi Mailing ListEveryone on the Comedi Mailing List

Thanks!Thanks!

Questions?Questions?