1. EE 472 – Senior Project Hang B. Lee, Applied Physics & EE Advisor: Prof. Robert Grober “Noise Characterization of A/D Converter on PIC Microcontroller”

2. PIC Microcontroller PIC: Programmable Interface Controller Modifiable by end user: -Software (C code) -Hardware (modification to circuitry) Common use in robotics and control applications Potential use in data acquisition or measurement EE 472 – Senior Project

3. Project Goal Understand noise characteristics of A/D Converter Investigate methods to minimize or eliminate noise Artificially enhance resolution – software methods EE 472 – Senior Project

4. 10-bit resolution 8 channels for analog input Throughput: 35,000 samples per sec Method of conversion: (i) sample and hold (ii) successive approximation A/D Converter EE 472 – Senior Project

5. Resolution What is maximum resolution? For 5V, maximum resolution ~ 5 mV 1 LSB represents 5mV increment EE 472 – Senior Project

6. A/D Converter Noise EE 472 – Senior Project Quantization noise (error due to discretizing) Thermal noise Reference voltage variations Etc. What is the sum of all these contributions?

7. Oversampling and Averaging EE 472 – Senior Project Artificially enhance resolution Cost efficient alternative to paying for higher resolution BUT …. Tradeoff throughput (High resolution means slower conversion speed) More CPU intensive

8. Requirements EE 472 – Senior Project Must be able to approximate sum of all noise contributions as white noise White noise has uniform power spectral density Two ways to check for this: (1) Histogram analysis (2) Take FT of autocorrelation

9. Data Measurement Built-in potentiometer / DC power supply Labview collects digital output values Histogram analysis EE 472 – Senior Project

10. Serial Interface Serial interface PIC chip with PC Receive streaming data from output pin Approaches taken: (1) Visual Basic – failed effort (2) Labview – better EE 472 – Senior Project

11. Visual Basic Approach EE 472 – Senior Project

12. Problems with Visual Basic Buffer check requires too much time Causes lag in data acquisition Too slow for collecting large number of data points EE 472 – Senior Project

13. Labview Waveform EE 472 – Senior Project

14. Waveform Close-up EE 472 – Senior Project

15. Another Waveform EE 472 – Senior Project

16. Histogram – 88 EE 472 – Senior Project

17. Histogram - 11 EE 472 – Senior Project

18. Histogram – 255 EE 472 – Senior Project

19. DC Histogram – 18 EE 472 – Senior Project

20. We understand that “effective” resolution is not nearly as good as maximum resolution Dithering may help – introduce white noise then oversample and average What Now? EE 472 – Senior Project