1. University of Tehran 1 Microprocessor System Design IO Applications Omid Fatemi (omid@fatemi.net)

2. University of Tehran 2 Outline LCD Stepper motor ADC and DAC Sensors PC parallel port

3. University of Tehran 3 New LCDs Interfacing Lower prices Display numbers, characters, graphics Integrated refreshing controller Ease of programming

4. University of Tehran 4 Pin Description

5. University of Tehran 5 Command Codes

6. University of Tehran 6 Example

7. University of Tehran 7 Programming LCD - Example

8. University of Tehran 8 Sending Data

9. University of Tehran 9 LCD Addressing

10. University of Tehran 10 LCD Timing

11. University of Tehran 11 LCD Instructions

12. University of Tehran 12 Stepper Motors more accurately controlled than a normal motor allowing fractional turns or n revolutions to be easily done low speed, and lower torque than a comparable D.C. motor useful for precise positioning for robotics Servomotors require a position feedback signal for control

13. University of Tehran 13 Stepper Motor Diagram

14. University of Tehran 14 Stepper Motor Step Angles

15. University of Tehran 15 Terminology Steps per second, RPM –SPS = (RPM * SPR) /60 Number of teeth 4-step, wave drive 4-step, 8-step Motor speed (SPS) Holding torque

16. University of Tehran 16 Stepper Motor Types –Variable Reluctance –Permanent Magnet

17. University of Tehran 17 Variable Reluctance Motors

18. University of Tehran 18 Variable Reluctance Motors This is usually a four wire motor – the common wire goes to the +ve supply and the windings are stepped through Our example is a 30 o motor The rotor has 4 poles and the stator has 6 poles Example

19. University of Tehran 19 Variable Reluctance Motors To rotate we excite the 3 windings in sequence –W1 - 1001001001001001001001001 –W2 - 0100100100100100100100100 –W3 - 0010010010010010010010010 This gives two full revolutions

20. University of Tehran 20 Unipolar Motors

21. University of Tehran 21 Unipolar Motors To rotate we excite the 2 windings in sequence –W1a - 1000100010001000100010001 –W1b - 0010001000100010001000100 –W2a - 0100010001000100010001000 –W2b - 0001000100010001000100010 This gives two full revolutions

22. University of Tehran 22 Basic Actuation Wave Forms

23. University of Tehran 23 Unipolar Motors To rotate we excite the 2 windings in sequence –W1a - 1100110011001100110011001 –W1b - 0011001100110011001100110 –W2a - 0110011001100110011001100 –W2b - 1001100110011001100110011 This gives two full revolutions at 1.4 times greater torque but twice the power

24. University of Tehran 24 Enhanced Waveforms better torque more precise control

25. University of Tehran 25 Unipolar Motors The two sequences are not the same, so by combining the two you can produce half stepping –W1a - 11000001110000011100000111 –W1b - 00011100000111000001110000 –W2a - 01110000011100000111000001 –W2b - 00000111000001110000011100

26. University of Tehran 26 Motor Control Circuits For low current options the ULN200x family of Darlington Arrays will drive the windings direct.

27. University of Tehran 27 Interfacing to Stepper Motors

28. University of Tehran 28 Vector Generation Hardware solutions –Logic design –State machine Software solutions –Microprocessor and output ports –timing

29. University of Tehran 29 Example

30. University of Tehran 30 Digital to Analog Converter

31. University of Tehran 31 Example – Step Ramp

32. University of Tehran 32 Analog to Digital

33. University of Tehran 33 V in Range

34. University of Tehran 34 Timing

35. University of Tehran 35 Interfacing ADC

36. University of Tehran 36 Example

37. University of Tehran 37 Temperature Sensor

38. University of Tehran 38 Printer Connection

39. University of Tehran 39 IO Base Address for LPT

40. University of Tehran 40 Printer’s Ports

41. University of Tehran 41 Selected Problems (Ch. 4)