Test your projects… ….from your PC!

Today’s Presentation Background Problem Statement Objectives Milestones Technical Approach Future Work Achievements; Conclusions Questions

The PC Based Oscilloscope Team Students: Todd M. Buelow, EE Michael Jendrysik, CprE Chris Justice, EE Mike McClimans, EE Brian J. Smith, EE Advisor: Dr. David Carlson Associate Professor of Electrical & Computer Engineering

Background High cost of Oscilloscopes makes them out of reach for many Simple, low-cost oscilloscope are handy for small electronics projects Useful to the typical college student and the electronic hobbyist

Problem Statement To research, design, develop, and test a device that will take voltage vs. time measurements, as an oscilloscope does, and output those results to a PC To present the digitized voltage measurements to the user in the form of a live waveform display via custom software

Objectives Basic oscilloscope functionality A self-contained module Nine pin serial port connector to interface with a PC BNC connections for scope probes Control done via software

Milestones Design hardware layout Develop companion software Develop microcontroller firmware Fabricate PCB Assemble circuit Test and debug the module and software

PC Based Oscilloscope Basic Hardware Layout

Hardware Design Options ISA Card USB Port Parallel Port Serial Port

Hardware Design Options Microcontroller ADC Simple, but slow External ADC Faster, but more complex Software selectable gain control Convenient, flexible, but considerable added complexity

Hardware Design Options Static Gain Simple, but not as flexible Single ended input Simple, no need for inverting supply, provides more precise ADC readings, but impractical for real use Positive and negative input Flexible input signals, necessary for some applications requires inverting supply, less precise ADC readings potential noise

PCB Layout Considerations PCB Design issues –Sensitive analog signals mixed with noisy digital circuitry –Small form-factor –Development board (ease of debug) –Donated board turn

PCB Layout Considerations Good PCB layout implementation –Separate analog and digital circuitry –Path to isolated analog ground –Ground fill, ground plane –Power planes –Bypass, bypass, bypass –All surface mount components –10 10 spacing rules –4 layer board (Outer 2 layers are signal layers, inner two are power and ground planes)

+ - CHA+ + - CHB+ CHB- CHA- Data bus Memory address Data Serial Translator 9 pin Connector Serial to / from host PC Test signal generator Regulated power outputs Test output CDJ 10/14/98 Probe hardware block diagram PC-Based oscilloscope Instrumentation amplifiers Analog to digital converter Memory Microcontroller Power supply External power supply (unregulated) Digital Trigger Address counter Control

PC Based Oscilloscope Firmware Goal: sampling, storing, & data communication with host PC C or Assembly? Assembly chosen due to –Tremendous amount of freeware example code –Free compilers/emulators –C compilers are all third party and little source code

PC Based Oscilloscope Firmware Three stages of development First version –Check for commands from host and tell the host when messages received correctly –Set output pins to DC for 5 seconds after receiving a bad command –Send out square waves on output pins otherwise Second Version –Basically a voltmeter –Samples every few seconds and sends to host Third version –All the bells & whistles (full speed sampling, triggering, data buffering in memory)

PC Based Oscilloscope Firmware Yes. No. Keep filling. No. Continue polling for PC command. No. Yes. No. Look for new command. Yes. Send more. Yes. Analyze command. Yes. Prepare for continuous output. No. Prepare for trigger mode. Startup. Initialize Port & Data Initialize Ports, Data Look for host PC PC comman d present? Send data to serial port. Store Data from ADCs Send data in memory out to serial port. Store data. Go to next memory address. Is trigger condition met? Is there more data in the memory? Is memory full? Does PC demand streaming data? Select Channel, read data from ADC.

Host PC Software Software Development –Visual C++ 6 –Microsoft Foundation Class (MFC) –Dialog based –Compatible with Microsoft Windows 95/98 Software Features –Time/Voltage scaling –Individual channel control –Measurements, triggers –Adjustable ground –User friendly –Possessing the look and feel of real oscilloscope

Host PC Software Software Operation –Win32 file handles for serial operation No device driver needed –Trigger mode –Streaming mode –Receive data via serial port

Host PC Software Screenshot Setup triggers for data collection. Sample data at a regular basis, or only when you want it. Save settings between testing sessions. Take measurements and cut & paste the results to a lab report. Add or subtract 2 waveforms. Modify the time scaling with ease. Change Voltage scaling at the push of a button.

Future Work Software Firmware Hardware Additions: –More math functions (FFT, etc.) –Matlab and Excel datalinks in software Marketing strategies

What We Learned Working together Communication among team members Goal setting and co-motivation

Any questions?