Device Interface Board for Wireless LAN Testing

1. Device Interface Board for Wireless LAN Testing Team May 06-15 Client ECpE Department Faculty Advisor Dr. Weber Team Members Matthew Dahms – EE Justine Skibbe – EE Joseph Chongo – EE February 9, 2006

2. Presentation Outline • Project Overview • Introduction • Problem Statement • Operating Environment • Intended Users & Uses • Assumptions and Limitations • End-Product Description • Project Activities • Previous Accomplishments • Technology Considerations • Present Accomplishments • Planned Activities • Resources & Schedule • Estimated Resources • Schedules • Closure Materials • Additional Work • Lessons Learned • Risk & Management • Closing Summary Figure 1: Teradyne Lab Entrance

3. 1 0 1 0 D3 D2 D1 D0 voltage time Header Data Packet Definitions • ASK modulation – Amplitude shift keying. In this modulation scheme the amplitude is varied to indicate logic 0’s and 1’s • DUT – Device under test (positive edge D flip-flop) • FPGA – Field programmable gate array. Used to test the DUT after receiving signals from the Teradyne tester • Header – Preamble bits sent prior to the sending of information in a data packet Figure 2: Data Packet and Header

4. Definitions (cont.) • NRZ – Non-return to zero. Using NRZ, a logic 1 bit is sent as a high value and a logic 0 bit is sent as a low value. • PLL – Phase-locked loop • RZ – Return to zero. This is the opposite of NRZ data. The signal state is determined by the voltage during the first half of each data binary digit.  The signal returns to a resting state (called zero) during the second half of each bit. • Teradyne Integra J750 – Tester donated to Iowa State University by Teradyne.  It is used in the testing of printed circuit boards and integrated circuits.

5. Project Overview

6. Acknowledgement • Dr. Weber • Nathaniel Gibbs • Jason Boyd

7. Project Overview • Problem Statement • In Fall 2004, ISU’s ECE Department introduced a senior design project with the goal of developing a wireless interface capable of receiving test signals and transmitting results to the department’s Teradyne Integra J750 tester. • For this project, the goal is to modify the current setup so that the wireless interface shall be capable of recovering a clock signal transmitted by the Teradyne system.  Figure 3: Teradyne Integra J750

8. Project Overview • Assumptions • A sufficient clock-training signal can be sent by the Teradyne J750 over the S/R network to initialize the clock recovering circuitry. • The clock recovering circuitry will be able to interact with the existing FPGA. • The current wireless communication network can transmit up to five feet.  This assumption is based on the May05 team’s documentation. • The phase difference between the system clock of the Teradyne J750 and the recovered clock at the wireless interface will not be greater than the overall system clock frequency.

9. Project Overview • Limitations • The Teradyne J750 is sensitive to temperature fluctuations and must operate within the calibrated temperature. • To avoid the loss of data, the maximum rate at which user can send data is at 115.2 Kbps. • The existing transmitter and receiver communicate at 916.5 MHz.  Therefore, nearby wireless signals at similar frequencies may disrupt the setup. • The communication link shall be limited to one frequency. • Limited to using only one FPGA.  Using two additional FPGA’s, it would be possible to encode/decode the clock and test data into a single data stream. Figure 4: Temperature Requirements

10. Project Overview • Intended Users • The user has knowledge in electrical and/or computer engineering. • The user has previous experience testing circuits with the Teradyne J750. • Intended Uses • Functional test of a digital device • (Future) Wireless chipset test

11. Project Overview • End-Product and Other Deliverables • Wireless interface with clock recovery circuit • Demonstration of wireless test • Update the manual for wireless test operation Figure 5: Cover page of wireless manual

12. Project Activities

13. Previous Accomplishments • May 05-29 Accomplishments • Parallel-Serial Conversion • Transmitters and Receivers • Processing Device

14. Previous Accomplishments • Parallel-Serial Conversion • Needed to convert parallel test data into serial test data • Chose to use a shift register Figure 6: Shift Register attached to daughterboard

15. Previous Accomplishments • Transmitters and Receivers TRM1 RCV1 RCV2 TRM2 Figure 7: Tx/Rx PCBs

16. Previous Accomplishments • FPGA • Used to recognize header signal • Identifies test data • Presents test data to DUT • Presents reply to S/R network Figure 8: FPGA

17. Figure 9: Final System Setup

18. Project Activities • Project Definition • Part of the May 05 team’s project definition was to include a clock recovery circuit, but due to timing constraints was unable to do so. • May 06 goal is to integrate a PLL for clock recovery with the existing network.

19. Project Activities System Block Diagram Figure 10: Proposed final setup block diagram

20. Project Activities • Technology Considerations • Manchester vs. PLL • NRZ to RZ Conversion

21. Technology Considerations Manchester Encoding The waveform for a Manchester encoded bit stream carrying the sequence of bits 110100 Figure 11: Graphical representation of Manchester encoding

22. Technology Considerations • Manchester Encoding • Very easy to implement • Clock phase and frequency are both present • Too fast for current transmitters and receivers!

23. Technology Considerations • Phase Locked Loop • Must be “trained” • Test data must follow a training signal • More difficult to implement • Don’t have to build new transmitters and receivers

24. Project Activities Figure 12: Internal Components of a PLL

25. Project Activities • Phase Detector • Type I – XOR • *Type II – Generates lead or lag pulses • Voltage Controlled Oscillator (VCO) • Centered at 115.2 KHz • Frequencies too far off of center frequency will not lock

26. Project Activities Figure 13: Internal PLL Schematic

27. Project Activities • Monostable Multivibrators • Chosen to convert NRZ data to RZ data • Must use an external RC combination to specify pulse widths

28. Project Activities Figure 14: NRZ to RZ converter circuit with I/O waveforms

29. Project Activities • Software • FPGA serves as “brains” of system • Verilog chosen by previous team to program FPGA • New prototype code complete

30. Project Activities • Present Accomplishments • Hardware Selected • Previous team’s project setup and tested • PLL • Monostable Multivibrators • Software • Prototype control software for FPGA written • IG-XL test template written

31. Project Activities • Planned Design/Test Activities • Build and test NRZ to RZ converter • Build and test PLL circuitry • Put new circuitry on printed circuit board • Modify FPGA code as necessary • Test functional range of wireless interface

32. Resources & Schedule

33. Expected • Original • Actual Schedule

34. Schedule (cont.) • Expected • Original • Actual

35. Personal Effort Personal Time Committment *Completed hours ** Left on Co-op

36. Previous Team Resources

37. Financial Resources (w/o labor)

38. Financial Resources (w/ labor)

39. Closure Materials

40. Risk Management • Risk: Losing Team Member • Management: All members keep detailed & organized notes • Risk: Loss of Data • Management: All data will be backed up using team gmail account • Risk: Parts Malfunction • Management: Meticulous care in ESD procedures (using ESD bands)

41. Closing Materials • Lessons Learned • What technical knowledge was gained? • FPGA implementation • Teradyne Integra J750 usage • Clock recovery methods • System integration

42. Closing Materials • Lessons Learned • What went well? • May05 System still works! • Teamwork • Learned to work in arctic environments (19 degrees C inside Teradyne lab) • What did not go well? • Locating May05 equipment • Initial Teradyne J750 setup and test • Uploading program to FPGA • FPGA input pins

43. Closing Materials • Closing Summary • Problem – Integrate clock recovery circuitry into current system • Solution • Use PLL for clock recovery • Modify FPGA program to incorporate new components

44. Questions? Questions???

45. Thank You