Practical Training on Arduino

7/29/2019 Practical Training on Arduino

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B. amil ZDEN Serkan TARINDepartment of Mechanical Engineering

Middle East Technical University

ME407

Microcontrollers & Arduino

Seminar

Note: This material is adopted from

Dr. Kokus ME 461 Lecture Notes


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Outline

Development Procedure

Hardware

Software

Preprocessor Commands

Arduino Example Functions

Serial Port

Digital I/O Ports

Motor Drive (Step, Servo)

ADC

PWM

Misc. functions

ME407 Microcontrollers&Arduino

Seminar


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Hardware Test / Development

Procedure

Build the basic PIC circuit on the breadboard. Keep everything tidy.

Make sure to keep all leads as short as possible.

Pay attention to electrolytic capacitors:

Their polarities are marked on their packages.

Before powering up, double-checkall connectionsand voltage polarities.

Connect your circuit to the serial port of your computer.


Seminar


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Hardware Test / Development

Procedure Make sure that the power supply is disconnected

from your circuit and turn the power supply on and

make sure that voltage is set around 7-9 Volts.

Turn the power supply off, connect your circuit on,and turn the supply back on.

Keep your eye on the current indicator, and if yoususpect that the circuit draws too much current,immediately turn the supply off.

Make sure to check the supply voltage of thePICmicro: Vdd = 4.5V to 5.5V (at most).


Seminar


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Programming PIC via

Programmer

BasicCode*.bas PIC Basic

Compiler

compile

Program the PIC

PC

RS232Parallel port

USB

PICPIC Programmer

Hex Code*.hex

download

PIC Programmer

Software

5ME407 Microcontrollers&Arduino

Seminar


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Programming PIC via

Bootloader

CCode*.c file PIC

Compiler

compile

Download program

to the PIC

PC

RS232PIC with bootloader

previously programmed

Hex Code*.hex

download

PIC ProgrammerSoftware

a. b. koku METU ME

Lectures


Seminar


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Booting the Loader

By default the bootloader

runs at each program start

If the a download attempt is

detected, the program is

read from the PC and loaded

into the PICs program area,and it will be executed

If no download attempt is

detected, last loadedprogram will be executed.

7

Program Memory

Free Memory

User Program

Bootloader code


Seminar


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CCS C Compiler

The CCS C compiler, which is developed by

Customer Computer Services (CCS), supports

almost all devices you can find in the market:

PIC12x

PIC16x

PIC18x

Compiler is quite compatible with ANSI C.

Quality of compiled code is very good. The optimizer does a good job in compressing the

code.


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Bit / Byte


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Analog / Digital


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ARDUINO Uno General View


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Microcontroller ATmega328

Operating Voltage 5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

Digital I/O Pins 14 (of which 6 provide PWM output)

Analog Input Pins 6

DC Current per I/O Pin 40 mA

DC Current for 3.3V Pin 50 mA

Flash Memory32 KB (ATmega328) of which 0.5 KB used

by bootloader

SRAM 2 KB (ATmega328)

EEPROM 1 KB (ATmega328)

Clock Speed 16 MHz


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ARDUINO Uno Power


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The Arduino Uno can be powered via the USB connection or with an external power

supply

VIN. The input voltage to the Arduino board when it's using an external powersource (as opposed to 5 volts from the USB connection or other regulated powersource). You can supply voltage through this pin, or, if supplying voltage via the

power jack, access it through this pin.

5V. This pin outputs a regulated 5V from the regulator on the board. The board canbe supplied with power either from the DC power jack (7 - 12V), the USB connector(5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins

bypasses the regulator, and can damage your board. We don't advise it.

3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current drawis 50 mA.

GND. Ground pins.


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ARDUINO Uno I/O


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Each of the 14 digital pins on the Uno can be used as an input or output,

using pinMode(), digitalWrite(), and digitalRead()functions. They operate

at 5 volts. Each pin can provide or receive a maximum of 40 mA.

Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data.These pins are connected to the corresponding pins of the ATmega8U2 USB-to-

TTL Serial chip.

External Interrupts: 2 and 3. These pins can be configured to trigger an interrupton a low value, a rising or falling edge, or a change in value. See

the attachInterrupt() function for details.

PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output withthe analogWrite() function.


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ARDUINO Uno I/OThe Uno has 6 analog inputs, labeled A0 through A5, each of which

provide 10 bits of resolution (i.e. 1024 different values). By default they

measure from ground to 5 volts, though is it possible to change the upperend of their range using the AREF pin and the analogReference()

function


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4 | Install the drivers

Plug in your board and wait for Windows to begin it's driver installation

process. After a few moments, the process will fail, despite its best efforts

Click on the Start Menu, and open up the Control Panel. While in the Control Panel, navigate to System and Security. Next, click on

System. Once the System window is up, open the Device Manager.

Look under Ports (COM & LPT). You should see an open port named

"Arduino UNO (COMxx)"

Right click on the "Arduino UNO (COmxx)" port and choose the "Update

Driver Software" option.

Next, choose the "Browse my computer for Driver software" option.

Finally, navigate to and select the Uno's driver file,

named "ArduinoUNO.inf", located in the "Drivers" folder of the ArduinoSoftware download (not the "FTDI USB Drivers" sub-directory).

Windows will finish up the driver installation from there.

If needed step by step installation link: http://arduino.cc/en/Guide/UnoDriversWindowsXP


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5 | Launch the Arduino application

6 | Open your code


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7 | Select your board


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8 | Select your serial port


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9 | Upload the program

Simply click the "Upload" button in the environment. Wait a few seconds - you

should see the RX and TX leds on the board flashing. If the upload is

successful, the message "Done uploading." will appear in the status bar.

For more information visit http://arduino.cc/en/Guide/Windows


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Other Arduinos


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Arduino Mega 2560

Arduino Motor Shield

Arduino Micro Arduino WiFi Shield

Arduino Proto Shield


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Arduino Libraries


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Standard Libraries

EEPROM - reading and writing to "permanent" storage

Ethernet - for connecting to the internet using the Arduino Ethernet Shield

Firmata - for communicating with applications on the computer using a standard

serial protocol.

LiquidCrystal - for controlling liquid crystal displays (LCDs)

SD - for reading and writing SD cards

Servo - for controlling servo motors

SPI - for communicating with devices using the Serial Peripheral Interface (SPI) Bus


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Arduino Libraries


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SoftwareSerial - for serial communication on any digital pins. Version 1.0 and

later of Arduino incorporate Mikal Hart's NewSoftSerial library as SoftwareSerial.

Stepper- for controlling stepper motors

WiFi - for connecting to the internet using the Arduino WiFi shield

Wire - Two Wire Interface (TWI/I2C) for sending and receiving data over a net ofdevices or sensors.

More info at: http://arduino.cc/en/Reference/Libraries

References: http://arduino.cc/en/Reference/HomePage


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Arduino Code Basics


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The setup() function is called when a sketch starts. Use it to initialize variables,

pin modes, start using libraries, etc. The setup function will only run once, after

each powerup or reset of the Arduino board.

loop() function does precisely what its name suggests, and loops consecutively,

allowing your program to change and respond as it runs. Code in

the loop() section of your sketch is used to actively control the Arduino board.

void setup() {// put your setup code here, to run once:

}void loop() {// put your main code here, to run repeatedly:

}


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Arduino Code Basics


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const int buttonPin = 3;

// setup initializes serial and the button pin

void setup() {

Serial.begin(9600);

pinMode(buttonPin, INPUT);

}

// loop checks the button pin each time,

// and will send serial if it is pressed

void loop() {

if (digitalRead(buttonPin) == HIGH)

Serial.write('H');else

Serial.write('L');

delay(1000);

}


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Arduino Code Examples -1


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To build the circuit, attach a 220-ohm resistor to pin 13. Then

attach the long leg of an LED (the positive leg, called the

anode) to the resistor. Attach the short leg (the negative leg,

called the cathode) to ground.

http://fritzing.org/

/ *Bl i nk

Turns on an LED on f or one second, t hen

of f f or one second, r epeat edl y.

Thi s exampl e code i s i n t he publ i cdomai n.*/

/ / Pi n 13 has an LED connect ed on mostAr dui no boar ds. / / gi ve i t a name: i nt l ed = 13;


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/ / t he set up r out i ne r uns once when you pr ess r eset : voi d set up( ) {

/ / i ni t i al i ze t he di gi t al pi n as an out put .

pi nMode( l ed, OUTPUT) ;}

/ / t he l oop r out i ne r uns over and over agai nf or ever : voi d l oop( ) {

di gi t al Wr i t e( l ed, HI GH) ; / / t ur n t he LED on( HI GH i s t he vol t age l evel )

del ay( 1000) ; / / wai t f or a seconddi gi t al Wr i t e( l ed, LOW) ; / / t ur n t he LED of f by

maki ng t he vol t age LOW

del ay( 1000) ; / / wai t f or a second}


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Analog Read Serial

This example shows you how to read analog input

from the physical world using a potentiometer (10k

ohm)

The Arduino has a circuit inside called an analog-to-

digital converterthat reads this changing voltage

and converts it to a number between 0 and 1023.

In between, analogRead() returns a number between

0 and 1023 that is proportional to the amount ofvoltage being applied to the pin.


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Arduino Code Examples - 3


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Pulse Width Modulation, or PWM, is a technique for getting analog results

with digital means. Digital control is used to create a square wave, a signal

switched between on and off. This on-off pattern can simulate voltages in

between full on (5 Volts) and off (0 Volts) by changing the portion of the time

the signal spends on versus the time that the signal spends off.


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Arduino's PWM frequency at about 500Hz,

the green lines would measure

2 milliseconds each.

A call to analogWrite() is on a scale of 0 -

255, such that analogWrite(255) requests

a 100% duty cycle (always on), and

analogWrite(127) is a 50% duty cycle (on

half the time) for example.


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Stepper motors, due to their unique design, can be controlled to a high degree

of accuracy without any feedback mechanisms. The shaft of a stepper, mounted

with a series of magnets, is controlled by a series of electromagnetic coils that

are charged positively and negatively in a specific sequence, precisely moving it

forward or backward in small "steps".


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Unipolar Stepper Circuit


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Code/ ** Mot or Knob** A st epper mot or f ol l ows t he t ur ns of a pot ent i omet er

* ( or ot her sensor ) on anal og i nput 0.*/

#i ncl ude

/ / change thi s t o the number of st eps on your motor

#def i ne STEPS 100

/ / creat e an i nst ance of t he st epper cl ass, speci f yi ng/ / t he number of st eps of t he mot or and t he pi ns i t ' s/ / at t ached t oSt epper st epper ( STEPS, 8, 9, 10, 11) ;

/ / t he pr evi ous r eadi ng f r om t he anal og i nput i nt pr evi ous = 0;


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voi d setup( ){

/ / set t he speed of t he mot or t o 30 RPMsst epper . set Speed(30);

}

voi d l oop( ){

/ / get t he sensor val uei nt val = anal ogRead(0) ;

/ / move a number of st eps equal t o t he change i n t he/ / sensor r eadi ngst epper . step( val - pr evi ous) ;

/ / r emember t he pr evi ous val ue of t he sensor

pr evi ous = val ;}


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QUESTIONS


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Bit, byte vs kavramlar Alabilecekleri siteler


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Generic CCS C Program

A generic C program for PICmicro constitutes

Preprocessor commands / directives:

Hardware Information PICMicro type, clock frequency, etc.

Configuration of PICMicro

Configuration (mode) bits

Parameters of peripheral units Compiler options and other declarations

Optimization option

Program starting address, file register declarations, etc.

Main program Initialization of peripheral units

Calling built-infunctions for the initialized units



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P C d (C d)


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Preprocessor Commands (Contd)

#f uses opt i ons tells the compiler about the configuration andoperating mode of the device:

HS option defines the oscillator type as high-speed resonator (>> 4MHz).

Other oscillator options are

XT (standard crystal with a typical. freq. of 4MHz)

LP (low power oscillator)

RC (resistor-capacitor oscillator)

NOWDT tells the compiler that no Watch Dog Timer is utilized. A safety measure in case the execution of the your program gets out of hand!

NOPROTECTspecifies that flash memory is NOT protected:

Resident program could be read/decompiled/reviewed without authorization.

NOLVP informs the compiler that no low voltage programming is to beallowed on this device.


P C d (C td)


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Preprocessor Commands (Contd)

#or g st ar t addr , f i nal addr {}

reserves memory in flash memory (ROM). #or g 0x1F00, 0x1FFF{} reserves the last 255-wordof the ROM for the bootloader (a.k.a. operating

system programof your PICmicro).

#opt opt i on tells the compiler optimizationlevel of your code:

0: lowest

9: highest (leads to the most-efficient compiled code)


CCS C F ti


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CCS C Functions

CCS C built-in functions covered: Serial port (RS-232 / UART)

Digital (discrete) I/O ports A/D converter

Pulse width modulator

Counters/timers Interrupts

Timer interrupts

External interrupt

Miscellaneous functions



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Di it l O t t F ti


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Digital Output Functions

CCS C provides a number of output functions:

out put _hi gh( PI N_X#) applies 5V to PIN_X#: # is a (bit) number between 0 and (usually) 7.

X is the port name (A, B, ..., G).

out put _l ow( PI N_X#) applies 0V to the output pin.

out put _bi t ( PI N_X#, st at e) applies either 5V or

0V to the pin depending on the state specified.

out put _X( val ue) applies a set of voltages to all

pins of port X depending on the given logic states.


Digital Input Functions


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Digital Input Functions

Here are some digital input functions of CCS C:

i nput ( PI N_X#) returns the logic state of PIN_X#:

5V 1 (High LS)

0V 0 (Low LS)

i nput _X( ) returns the entire logic states of port X.

Type of digital I/O can be specified through thefollowing preprocessor commands:

#use st andar d_i o( X) (in effect, if omitted)

#use f i xed_i o( X_out put s = PI N_X#, PI N_X#, . . . )

#use f ast _i o( X) (we shall prefer this one!)


Digital I/O Functions (Contd)


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Digital I/O Functions (Cont d)

When #use f ast _i o( X) is used, the compiler

performs digital I/O without (re)programming the

direction register (TRISX).

User must ensure TRISX is set correctly via

set _t r i s_X( st at e) :

Bits of byte statecorrespond to directions of the pins of port

X.

If bit is 1, that pin is defined as (1)nput.

Otherwise, it is an (0)utput pin.



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Example Digital I/O


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Example Digital I/ORB0

470

RB1

10 k

Vdd = 5V

ButtonLED

Write a C program for a

PIC16F877A interfacing with

a push button that toggles the

shownLED as the buttongets to be depressed.

Solution:

In this exercise, the PICmicroturns into a simple toggle flip/flopdriving a LED. LED and the button are connected to thePI N_B0 (output: 0) and PI N_B1 (input: 1) respectively. Assuming that

no other elements are connected to PORTB, port-pin directions

are simply set by set _t r i s_b( 0xFE) (remaining pins are defined as inputs!)

- Note that 0xFE (hex) = 0b11111110 (bin) = 254 (dec)


Example Digital I/O


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Example Digital I/O

#i ncl ude #f uses HS, NOWDT, NOPROTECT, NOLVP#use del ay( cl ock=20000000)#use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7)

#use f ast _i o( B) / * t r i s_b must be set pr oper l y! */#or g 0x1F00, 0x1FFF {}#opt 9

voi d mai n( ) {i nt 1 Q = 0;

set _t r i s_b( 254) ; / * onl y PI N_B0 i s def i ned as out put */pr i nt f ( "Program st ar t s. . . \ n\ r " ) ;

whi l e( TRUE) { / * i nf i ni t e l oop * /i f ( ! i nput ( PI N_B1) ) { / * when swi t ch i s depr essed. . . */

Q = ! Q; / * . . . t oggl e LED st at e */del ay_ms( 200) ; / * . . . wai t f or 0. 2s t o debounce */out put _bi t ( PI N_B0, Q) ; }; / * . . . out put LED st at e */

}}


Accessing RAM Directly


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Accessing RAM Directly

CCS C allows direct access to the RAM including the

(file) registers like PORTX:

#byt e t ag = addr ess associates the byte at the specifiedaddress with the given tag.

#bi t t ag = addr ess. n associates the nth bit of byte residing

at the specified address with the given tag.

While accessing PORTX registers, one must set thedirections of each pin correctly via set _t r i s_X( st at e)

function.

Some useful addresses (refer to the datasheet) are

PORTA = 0x05, PORTB = 0x06

PORTC = 0x07, PORTD = 0x08


Example 2b Digital I/O


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Example 2b Digital I/O#i ncl ude #f uses HS, NOWDT, NOPROTECT, NOLVP#use del ay( cl ock=20000000)#use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7)#use f ast _i o( B) / * t r i s_b must be set pr oper l y! */#or g 0x1F00, 0x1FFF {}#opt 9

#byt e PORTB = 0x06 / * cont r ol r egi st er f or Por t B */ #bi t SW = PORTB. 1 / * RB1 i s connect ed t o swi t ch */ #bi t LED = PORTB. 0 / * RB0 dr i ves a LED */

voi d mai n( ) {i nt 1 Q = 0;set _t r i s_b( 254) ; / * onl y RB0 i s def i ned as out put */pr i nt f ( "Program st ar t s. . . \ n\ r " ) ;whi l e( TRUE) { / * i nf i ni t e l oop * /

i f ( ! SW) { / * when swi t ch i s depr essed. . . */

Q = ! Q; / * . . . t oggl e LED st at e */del ay_ms( 200) ; / * . . . wai t f or 0. 2s t o debounce */LED = Q; }; / * . . . out put LED st at e */

}}



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Example Serial Port


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Example Serial Port

#i ncl ude / * PI CMi cr o Model : 16F877A */#f uses HS, NOWDT, NOPROTECT, NOLVP / * Devi ce conf i gur at i on */

#use del ay( cl ock=20000000) / * CLK f r equency: 20MHz * / #use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7) / * RS- 232 par amet er s */#or g 0x1F00, 0x1FFF {} / * Reser ve memor y i n ROM */#opt 9 / * Compi l er opt . l evel ( max) */

voi d mai n( ) {

char c;l ong nc = 0;pr i nt f ( *** PI C Typewr i t er ***\ n\ r " ) ;do{

c = get c( ) ; / * Get a char act er f r om PC */putc(c); / * Send i t back t o PC */nc++; / * Count char s * /i f ( nc == 13) pr i nt f ( " \ n" ) ; / * Li ne f eed */

} whi l e ( c! =0x11) ; / * Echo unt i l ct r l - Q */pr i nt f ( "\ n\ r No. of char act er s: %l d\ n\ r " , nc) ;whi l e( TRUE) ; / * I nf i ni t e l oop * /

}

As an illustration of these functions, let us write a simple C program

which turns the serial port monitor (siow) into a typewriter:



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A/D Conversion (Contd)


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A/D Conversion (Cont d)

The following functions are utilized to select a

ADC channel and to read the result:

set _adc_channel ( n) selects the pin RAn as theinput channel.

r ead_ADC( ) returns the 10-bit result.

One must wait at least 10 to 20 s beforereading the result.

ADC unit can generate an interrupt when a

conversion is done. A useful feature for time-sensitive apps.


Example 3 ADC


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Example 3 ADC470

a

b

c

d

e

f

g K

470

LS 5015-20

RC4

RC5

RC3

RD0

RD1

RD3

RD2

Vdd = 5V

20 k(pot.)

470 RA0

AN0

a

b

c

d

e

f

g

Consider a PIC16F877A connected to a seven segment display (SSD)

along with a 20k potentiometer as illustrated. Write a C program suchthat the PIC shows the applied voltage at RA0 pin as a hexadecimal

number (0 F) on the SSD. Furthermore, hex. numbers 0 and F mustblink on the display while the PIC is to send the strings lowand high

respectively over the RS-232.



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Example 3 C Code


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Example 3 C Code#i ncl ude #devi ce ADC=10 / * devi ce has 10- bi t ADC */#f uses HS, NOWDT, NOPROTECT, NOLVP#use del ay( cl ock=20000000)#use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7)

#use f ast _ i o( C)#use f ast _i o( D)#or g 0x1F00, 0x1FFF {}#opt 9

voi d ss_di sp( i nt num) { / * seven segment di spl ay r out i ne */

/ // / Due t o t hi s def i ni t i on, di sp_dat a now r esi des i n ROM!/ /

byt e const SSDat a[ 16] = {123, 80, 103, 117, 92, 61, 63, 120,127, 125, 126, 31, 7, 87, 47, 46};

i f( num < 16) {out put _c( ( SSDat a[ num] & 240) >>1) ;out put _d( SSDat a[ num] & 15) ;

}}


Example 3 C Code (Contd)


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a p e 3 C Code (Co t d)voi d mai n( ) {

l ong adval ;set _t r i s_c( 128) ; set _t r i s_d( 0) ; / * def i ne I / O pi ns f i r st * / out put _c( 0) ; out put _d( 0) ; / * cl ear di spl ay */set up_por t _a( ALL_ANALOG) ; / * set up ADC */set up_adc( ADC_CLOCK_I NTERNAL) ;set _adc_channel ( 0) ;pr i nt f ( "Pr ogr am st ar t s. . . \ n\ r " ) ;whi l e( TRUE) {

del ay_us( 200) ; / * make sure ADC i s r eady */ adval = r ead_ADC( ) ; / * r ead 10- bi t r esul t */

ss_di sp( adval >>6) ; / * di spl ay ( adval / 64) */i f ( adval 960) { / * t oo hi gh or t oo l ow? */

i f ( adval 960) pr i nt f ( "Hi gh\ n\ r " ) ;del ay_ms( 200) ; / * bl i nk t he number . . . */ out put _c( 0) ; out put _d( 0) ; / * . . . on t he di spl ay */del ay_ms( 200) ;

}}

}


Example 4 PWM


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p

470 a

b

c

d

e

f

g K

470

LS 5015-20

RC4

RC5

RC3RD0

RD1

RD3

RD2

Vdd

= 5V

20 k(pot.)

470 RA0

RC2

470

CCP1

AN0

Consider a PIC16F877A connected to a SSD along with a 20k pot. Write aC program such that the PICMicro shows the applied voltage at RA0 pin as a

Hex. number (0 F) on the SSD. Furthermore, it is to adjust the brightness of the

LED (connected to the pin of CCP1) via PWM as the the voltage on RA0 varies.


Seminar

Example 4 PWM


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pvoi d mai n( ) {

l ong adval ;set _t r i s_c( 128) ; set _t r i s_d( 0) ; / * def i ne I / O pi ns f i r st * / out put _c( 0) ; out put _d( 0) ; / * cl r 7- segment di spl ay */

set up_ccp1( CCP_PWM) ; / * conf i gur e CCP1 as PWM */setup_t i mer _2( T2_DI V_BY_1, 255, 1) ; / * PWM f r equency: ~20kHz */

set up_por t _a( AN0) ; / * onl y AN0 i s used her e! */set up_adc( ADC_CLOCK_DI V_2) ; / * T_AD = 2*T_CLK */

set _adc_channel ( 0) ;

pr i nt f ( "Progr am st ar t s. . . \ n\ r " ) ;whi l e( TRUE) {

del ay_us( 200) ;adval = r ead_ADC( ) ; / * r ead 10- bi t r esul t */

set _pwm1_dut y( adval ) ; / * d( %) = 100*adval / 1024 */ ss_di sp( adval >>6) ; / * di spl ay ( adval / 64) */

}}


Seminar


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Timer 1 Model


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72Timer Interrupt

Internal

PICmicroClock

Internal

PICmicro

Clock

External

Frequency

Source

External

Frequency

Source

Frequency

Divider

Frequency

Divider

8-bit

Counter

8-bit

Counter

set _t i mer 1( val ue)

T1_DI V_BY_1T1_DI V_BY_2T1_DI V_BY_4T1_DI V_BY_8

get _t i mer 1( )

a

bRC0/T1CK1

a:T1_I NTERNALb:T1_EXTERNAL or

T1_EXT_SYNCH

(20 MHz / 4)

D

CLK

Q

a:T1_I NTERNAL orT1_EXTERNAL

b:T1_EXT_SYNCH

a

bD-F/F


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Example 5a Timer0


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#i ncl ude #f uses HS, NOWDT, NOPROTECT, NOLVP#use del ay( cl ock=20000000)#use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7)#use f ast _ i o( B)#or g 0x1F00, 0x1FFF {}

#opt 9#bi t SW = 0x06. 1 / * RB1 i s t he swi t ch i nput */

voi d mai n( ) {i nt count ;

set _t r i s_b( 255) ; / * Al l pi ns ar e i nput s */ set up_count ers( RTCC_EXT_L_TO_H, RTCC_DI V_1) ; / * Set up RTCC */set _t i mer 0( 0) ; / * I . C. = 0 */whi l e( TRUE) {

count = get _t i mer 0( ) ; / * Read ct r 0 */i f( ! SW) { / * When SW i s depr essed. . . */

pr i nt f ( "Count er0 = %u\ n\ r " , count ) ; / * . . . send i t out ! * / del ay_ms( 200) ; }; / * Wai t 200 ms t o debounce */

}}


Seminar

Example 5b Timer1


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#i ncl ude #f uses HS, NOWDT, NOPROTECT, NOLVP#use del ay( cl ock=20000000)#use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7)#use f ast _ i o( B)#or g 0x1F00, 0x1FFF {}

#opt 9#bi t SW = 0x06. 1 / * RB1 i s t he swi t ch i nput */

voi d mai n( ) {l ong count ;

set _t r i s_b( 255) ; / * Al l pi ns ar e i nput s */ set up_t i mer_1( T1_EXTERNAL| T1_DI V_BY_1) ; / * Set up Ti mer 1 */set _t i mer 1( 0) ; / * I . C. = 0 */whi l e( TRUE) {

count = get _t i mer 1( ) ; / * Read ct r 1 */i f( ! SW) { / * When SW i s depr essed. . . */

pr i nt f ( "Count er 1 = %l u\ n\ r " , count ) ; / * . . . send i t out ! * / del ay_ms( 200) ; }; / * Wai t 200 ms t o debounce */

}}


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Interrupt Functions


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77

In CCS C, ISRs (interrupt-handlerfunctions) are marked up via a compilerdirective: #I NT_XXXX where XXXX stands for the type of interrupt.

The interrupt service procedures are embedded inside this function.

Interrupts must be enabled at the beginning of main function:

enabl e_i nt er r upt s( I NT_XXXX) sets the interrupt enable flag at the givenlevel.

enabl e_i nt er r upt s( GLOBAL) enables all interrupts.

Other relevant built-in functions are di sabl e_i nt er r upt s( I NT_XXXX)

di sabl e_i nt er r upt s( GLOBAL) cl ear _i nt er r upt ( I NT_XXXX) clears the interrupt flag at the given level.

Interrupts available in PIC 16F877A are External interrupt (INT_EXT)

Timer interrupts (INT_RTCC, INT_TIMER1)

Change on (Port B) pin interrupt (INT_RB)

A/D conversion complete interrupt (INT_AD) Serial port interrupts (INT_RDA, INT_TBE)

And more... }

of major

interest


Seminar

Timer Interrupts


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Timer0 (RTCC) and Timer1 are frequently used to generate

(precise) periodic interrupts for timing-sensitive applications like

digital control systems!

When RTCC orTimer1 counter overflows, it generates an interrupt.

Once the timer is set up in the main function, its interrupt is enabled.

Timers are set up such that the internal clock drives their counters.

The functions discussed in previous section are employed for this

purpose:

Timer0 (or RTCC):

set up_count er s( RTCC_I NTERNAL, RTCC_DI V_n)

Prescaler: n {1, 2, 4, 8, ..., 256}

Timer1:

set up_t i mer _1( T1_I NTERNAL| T1_DI V_BY_n) Prescaler: n {1, 2, 4, 8}


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Timer Interrupts (Contd)


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One can precisely set the desired interrupt frequency (fd)

[Hz] by selecting the initial value (m0) of timerX:

d

X

fnm

6

)1(80

105int2

Hence, at the beginning of ISR, the counter value is set

to m0 using set _t i mer X( m0) . As an illustration, letus calculate the initial counter value for timer0 (withRTCC_DI V_128 option: n = 128) if fd = 750 Hz:

20452256750128

105int26)01(8

0

m


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Example 6a - C program


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/ // / Pr epr ocessor di r ect i ves ar e same as Exampl e 5a/ /l ong count = 0; / * Gl obal var i abl e */

#I NT_RTCC / * I SR f or t i mer 0- over f l ow i nt er r upt */ voi d i sr ( ) {count ++; }

voi d mai n( ) {set _t r i s_b( 255) ; / * Al l pi ns of Por t B ar e i nput s */ set up_count er s( RTCC_I NTERNAL, RTCC_DI V_256) ; / * Set up RTCC */set _t i mer 0( 0) ; / * I . C. = 0 */enabl e_i nt er r upt s( I NT_RTCC) ; / * Enabl e i nt er r upt s */ enabl e_i nt er r upt s( GLOBAL) ;whi l e( TRUE) {

i f( ! SW) { / * When SW i s depr essed. . . */

pr i nt f ( "Count er = %l u\ n\ r " , count ) ; / * . . . send i t out ! * /del ay_ms( 200) ; }; / * Wai t 200 ms t o debounce */

}}


Seminar

External Interrupt


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PIC16F877A allows the use of a single external

interrupt (INT_EXT):

External (interrupt) source must be connected toRB0/INT pin.

Before enabling the external interrupt, the type

of clock edge triggering intrerupt should be

specified:

ext _i nt _edge( L_TO_H) denotes the positive edge

of the clock triggers the interrupt.

ext _i nt _edge( H_TO_L) denotes the negative

edge of the clock triggers the interrupt.


Seminar

Example 6b External Interrupt


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In this example, the external clock is to be coupled to RB0/INT pin. We will

write a C program for the PICmicro such that it will count the pulses ofexternal clock and will send out counter values to the serial port monitor (PC)

whenever the pushbutton is depressed.

+

RB0/INT1

CD40106B

2

20 k

100 FVdd (14) = 5VV

ss(7) = GND

RB1

10 k

Vdd

= 5V

Button


Seminar

Example 6b External Interrupt


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/ // / Pr epr ocessor di r ect i ves ar e same as Exampl e 5a/ /l ong count = 0; / * Gl obal var i abl e */

#I NT_EXT / * I SR f or ext er nal B0 i nt er r upt */ voi d i sr ( ) {count ++; }

voi d mai n( ) {set _t r i s_b( 255) ; / * Al l pi ns of Por t B ar e i nput s */

ext _i nt _edge( L_TO_H) ; / * I nt er r upt on ( +) edge */enabl e_i nt er r upt s( I NT_EXT) ; / * Enabl e i nt er r upt s */ enabl e_i nt er r upt s( GLOBAL) ;whi l e( TRUE) {

i f( ! SW) { / * When SW i s depr essed. . . */

pr i nt f ( "Count er = %l u\ n\ r " , count ) ; / * . . . send i t out ! * /del ay_ms( 200) ; }; / * Wai t 200 ms t o debounce */

}}


Seminar

Pin-change Interrupt


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In 16F877A, pin change interrupt (INT_RB) is

used to detect the logic state changes at pin

RB7-RB4. If there is any change in these four inputs,

PICmicro generates an interrupt.

This interrupt is intended forkeyboard wake-up Microchip does not recommend the utilization of this interrupt

for any other applications.

Any read or write to Port B (say RB3-RB0) clears the

mismatch condition.


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Example 6c Pin Change Interrupt


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In this exercise, we would like to develop a C program for PICmicro so that the

microcontroller measures the input frequency (Hz) of the external clock at RB7

and transmits that information through the serial port. Note that for testing

purposes,a LED coupled to RB1 pin gets toggled whenever a pin-changeinterrupt is generated.

RB1

470

+

RB71

CD40106B

2

20 k

100 FV

dd

(14) = 5V

Vss (7) = GND


Seminar

Example 6c RB Change Interrupt#i l d 16F877A h


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#i ncl ude #f uses HS, NOWDT, NOPROTECT, NOLVP#use del ay( cl ock=20000000)#use r s232( baud=19200, xmi t =PI N_C6, r cv=PI N_C7)#or g 0x1F00, 0x1FFF {}

#use f ast _ i o( B)#opt 9#bi t LED = 0x06. 1 / * RB1 dr i ves a LED */

i nt count = 0; / * Gl obal var i abl es */shor t Q = 0;

#I NT_RB / * RB Change I SR */voi d i s r ( ) {

count ++; / * Count changes */Q = ! Q; / * Toggl e LED */

LED = Q; / * must R/ W t o Por t B bef or e cl ear i ng RBI F */cl ear _i nt er r upt ( I NT_RB) ; / * Cl ear RBI F */

}


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EEPROM Commands


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PIC 16F877A incorporate 256-byte non-volatile

memory.

The user can access EEPROM through thefollowing built-in functions of CCS C:

r ead_eepr om( addr ess) reads a byte from the

EEPROM at the specified address (8-bit). The address ranges between 0 and 255 for PIC 16F877A.

wr i t e_eepr om( addr ess, val ue) writes a byte

(value) to EEPROM at the specified address.

This function takes several milliseconds to execute.


Seminar

Watch Dog Timer (WDT)


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The WDT function is to monitor the computer system whether work

normally.

Otherwise, it will have some measures to fix up the system.

The main reason of the WDT is that software sometimes got lost: Enter infinite loops

Unexpected (conditional) branching puts the routine to go crazy.

The WDT unique intention is to reset the machine if certain

programmable timer expires. Therefore properly operating"software should "reset"WDT before it does!

For instance, if you program the WDT to 1 second, you should reset the

WDT timer before that happens.

If a routine gets lost, the WDT will reset your machine in onesecond, so not much is wasted.


Seminar

Practical Training on Arduino

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