University of Tehran 1 Microprocessor System Design IO Applications Omid Fatemi

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

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

University of Tehran 4 Pin Description

University of Tehran 5 Command Codes

University of Tehran 6 Example

University of Tehran 7 Programming LCD - Example

University of Tehran 8 Sending Data

University of Tehran 9 LCD Addressing

University of Tehran 10 LCD Timing

University of Tehran 11 LCD Instructions

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

University of Tehran 13 Stepper Motor Diagram

University of Tehran 14 Stepper Motor Step Angles

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

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

University of Tehran 17 Variable Reluctance Motors

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

University of Tehran 19 Variable Reluctance Motors To rotate we excite the 3 windings in sequence –W –W –W This gives two full revolutions

University of Tehran 20 Unipolar Motors

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

University of Tehran 22 Basic Actuation Wave Forms

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

University of Tehran 24 Enhanced Waveforms better torque more precise control

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

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

University of Tehran 27 Interfacing to Stepper Motors

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

University of Tehran 29 Example

University of Tehran 30 Digital to Analog Converter

University of Tehran 31 Example – Step Ramp

University of Tehran 32 Analog to Digital

University of Tehran 33 V in Range

University of Tehran 34 Timing

University of Tehran 35 Interfacing ADC

University of Tehran 36 Example

University of Tehran 37 Temperature Sensor

University of Tehran 38 Printer Connection

University of Tehran 39 IO Base Address for LPT

University of Tehran 40 Printer’s Ports

University of Tehran 41 Selected Problems (Ch. 4)