INTERFACING HARDWARE WITH MICROCONTROLLER

Transcription

1 INTERFACING HARDWARE WITH MICROCONTROLLER P.Raghavendra Prasad Final Yr EEE

2 What is a Microcontroller? A microcontroller (or MCU) is acomputer-on-a-chip. It is a type of microprocessor emphasizing self- sufficiency and cost-effectiveness effectiveness, in contrast to a general-purpose microprocessor (the kind used in a PC). The only difference between a microcontroller and a microprocessor is that a microprocessor has three parts - ALU, Control Unit and registers (like memory), whilethemicrocontroller has additional elements like ROM, RAM etc.

3 ATMEGA32/ATMEGA32L High-performance, Low-power AVR 8-bit Microcontroller Up to 16 MIPS Throughput at 16 MHz 32K Bytes of In-System Self-Programmable Flash 1024 Bytes EEPROM 2K Byte Internal SRAM Two 8-bit Timer/Counters, One 16-bit Timer/Counter In-System Programming by On-chip Boot Program Four PWM Channels 8-channel, 10-bit ADC Programmable Serial USART Internal Calibrated RC Oscillator External and Internal Interrupt Sources Power-on Reset 32 Programmable I/O Lines

4 ATMEGA32/32L ATMEGA16/16L 32K Bytes of Flash memory 1024 Bytes EEPROM 2K Byte Internal SRAM 16K Bytes of Flash memory 512 Bytes EEPROM 1K Byte Internal SRAM

5 ATMEGA32/16 ATMEGA32L/16L Operating Voltage V Operating Voltage V Speed Grades 0 16 MHz Speed Grades 0 8 MHz

6 Pin Diagram

7 COMPUTER C - CODE COMPILER c HEX - CODE MICRO CONTROLLER

8

9

10 STK200 Cable

11

12

13 Configuring PORT PINS Each PORT consists of three registers DDRX (Data Direction Register) PORTX PINX Where X = A, B, C, D

14

15 DDRX The DDXn bit in the DDRx Register selects the direction of pin n. IfDDXniswrittenlogicone,PXnisconfiguredasanoutputpin. If DDXn is written logic zero, PXn is configured as an input pin. Where n = 0,1,2 ---,7 For Example If DDRA = 0x0F ( ) The Lower bytes of PORTA are configured as output pins The Higher bytes of PORTA are configured as input pins

16 PORTX When PORTXn is configured as Input Pin Writing logic ONE to this pin, activates pull-up resistor. Writing logic ZERO to this pin, deactivates pull-up resistor When PORTXn is configured as Output Pin Writing logic ONE to this pin, drives the port pin HIGH Writing logic ZERO to this pin, drives the port pin LOW

17 PINX PINXn is used to read the value of particular port pin Independent of the setting of Data Direction bit DDRXn, the port pin can be read through the PINXn Register bit

18 ICCAVR ICCAVR, the ImageCraft s C Development Environment is a program for developing AVR microcontroller applications using the ANSI standard C language Full featured 30-day demo program can be downloaded from the ImageCraft web site

19 Getting Started with ICCAVR 1. Project>New 2. Project name and path 3. Project>Options 4. In the Compiler options, check Accept C++ Comments and Intel HEX as the output format 5. In the Target options, select ATmega32/Atmega16 under Device Configuration 6. Write the source code 7. Add the source file to the project by selecting Project>Add File(s) and select the file just written 8. Compile by selecting Project>Make Project or by clicking on the build icon 9. Open AVR ISP and download the hex file generated by ICCAVR, It is stored under the project name.

20 Sample program to generate Square wave on PORTA of ATMEGA32 #include<iom32v.h> #include<macros.h> Void delay(unsigned int i) { unsigned int k; While(i--) For(k=0;k<=500;k++); } Void main() { DDRA = 0xFF; // Configures PORTA Pins as Output pins While(1) { PORTA=0xFF; Delay(500); PORTA=0x00; Delay(500); }}}

21 Interfacing with Microcontroller LED Switches DC Motor Sensors Stepper Motor

22 LED Light Emitting Diode Maximum potential ti drop across LED will be approximately 2V. Maximum current tat can be allowed through am LED is approximately 30ma. Resistor should be added in series with LED to limit the current through it.

23 Calculating LED resistor value R = (Vs VL )/I Vs = supply voltage VL = Voltage drop across LED ( around 2V) I = 15 to 30 ma

24 LED s connected to 1. PORTA0 2.PORTB0

25 LED BLINK PROGRAM

26 DC Motor DC Motors are small, inexpensive and powerful motors used widely. These are widely used in robotics for their small size and high energy out. A typical DC motor operates at speeds that are far too high speed to be useful, and torque that are far too low. Gear reduction is the standard method by which a motor is made useful. Gear s reduce the speed of motor and increases the torque

27 Choosing a DC Motor DC Motor with Gear head Operating voltage 12V Speed Depends on our application Some available speeds in market 30 RPM 60 RPM 100 RPM 150 RPM 350 RPM 1000 RPM

28 Drive basics of DC Motor Red wire Black wire Direction of rotation Positive Negative Clock wise Negative Positive Anti clock wise Logic Logic Direction 1 0 Clock 0 1 Anti clock

29 Bi-Direction control of DC Motor H-Bridge Ckt using transistors for bidirectional driving i of DC motor Direction Clock wise Anti Clock wise Pulse to A and C B and D

30 H-Bridges in IC s to reduce the drive circuit complexity The most commonly used H-Bridges are L293D and L298 L293D has maximum current rating of 600ma L298 has maximum current rating of 2A Both has 2 H-Bridges in them These are designed to drive inductive loads such as relays, solenoids Can be used to drive 2 DC motors or 1 stepper motor

31

32

33 DRIVING OF DC MOTOR

34 Switches Active Low When pressed shorts the corresponding pin to ground Active high When pressed shorts the corresponding pin to Vcc

35 Active low Active high

36 INTERFACING SWITCHES

37 Sensors Commonly used sensors in the field of robotics are IR Digital sensors IR analog sensors

38 IR Digital sensors Transmitter IR led connected to 38KHz oscillator Receiver TSOP1738 IR Analog sensors Transmitter IR LED Receiver IR Photodiode

39 IR Analog sensor

40

41 STEPPER MOTOR STEPPER MOTOR is a brushless DC motor whose rotor rotates in discrete angular increments when its stator windings are energized in a programmed manner. Rotation occurs because of magnetic interaction between rotor poles and poles of sequentially energized stator windings. The rotor has no electrical windings, but has salient and/or magnetized poles.

42 4 Lead stepper 5 Lead stepper 6 Lead stepper 8 Lead stepper

43 Full Step driving of Stepper Motor Full step wave drive

44 Full Step driving of Stepper Motor Full step 2 phases active

45 Half Step driving of stepper motor

46

47 Choosing a Stepper motor 12 V operating voltage 1.8 degree step 6 Lead 250 t0 500 ma of current or Coil resistance of 20 ohms to 40 ohms Size and shape depends on application In most of the robotics cube shaped motors are preferred with frame size of 3.9 to 4 cm

48 Commonly used IC s for driving Stepper motor ULN2803 It has 8 channels It channel has maximum current rating of 500ma can be used to drive 2 unipolar stepper motors L293d L297 & L298

49 ULN2803

50

51 Bi Polar driving of Stepper Motor A B C D

52 DRIVING STEPPER MOTOR

53 Line Follower sensor1 sensor2 L D Left motor Right Mt Motor sensor3 Microcontroller

54 You can download this presentation at