Introduction to PIC Microcontrollers I/O PORTS, Interrupts ...eeeforum.weebly.com/uploads/1/0/2/5/10254481/pic_io_adc.pdf · Introduction to PIC Microcontrollers I/O PORTS, Interrupts,
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Department of Electrical & Electronics Engineering, Amrita School of Engineering
PIC16F877A Pin diagram from datasheet
Department of Electrical & Electronics Engineering, Amrita School of Engineering
DC Electrical Characteristics
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Source & Sink Currents
• Source current – coming out of microcontroller
• Sink current – going into the microcontroller
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Fan-out • Number of inputs that can be driven without damaging
the IC
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Programming Languages
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Programming Languages
Department of Electrical & Electronics Engineering, Amrita School of Engineering
C Programming /* C Program Structure
Sample Program */
# include <pic.h> // Directives
# define _XTAL_FREQ 4e6
unsigned int i ; // Declarations – data types
char H;
Void main () // function
{
command;
command;
}
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Flash an LED
R =
Port selection
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Flash an LED /* Flashing LED */
# include <pic.h> // Directives
unsigned int i ; // Declarations – data types
void main()
{
TRISB0=0;
while(1)
{
RB0=0;
for(i=1;i<=50;i++)
{
}
RB0=1;
for(i=1;i<=50;i++)
{
}
}
}
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Flash an LED /* Flashing LED */
# include <pic.h>
unsigned int i ;
void delay(int);
void main()
{
TRISB0=0;
while(1)
{
RB0=0;
delay(100);
RB0=1;
delay(100);
}
}
void delay(int d)
{
for(i=0; i<=d;i++)
{
}
}
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Flash an LED with pushbutton
R =
Port selection
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Flash an LED with pushbutton /* Flashing LED with pushbutton in another port */
# include <pic.h>
void main()
{
TRISB=0;
TRISC=1;
while(1)
{
RB0=0;
if(RC0)
RB0=~RB0;
}
}
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Interrupts
Suspends the execution of main program and a jump executed to an
interrupt service subroutine that takes some action and then returns
back
External resources and internal resources
External – switches, sensors, ADCs
Internal – Timers, CCP
Register used in control and status - INTCON
Department of Electrical & Electronics Engineering, Amrita School of Engineering
Flash an LED using Interrupts
Port selection
Port B RB0 – external interrupt pin
Port C – LED1
Port D – LED2
Department of Electrical & Electronics Engineering, Amrita School of Engineering
#include<pic.h>
#define LED1 RB1 //Create meaningful
names for pins
#define LED1_TRIS TRISB1
#define LED2 RB2
#define LED2_TRIS TRISB2
int i;
void main()
{
LED1_TRIS = 0; //LED1 is an output
LED2_TRIS = 0; //LED2 is an output
INTF = 0; //reset the external interrupt flag
INTEDG = 1; //interrupt on the rising edge
INTE = 1; //enable the external interrupt
GIE = 1; //set the Global Interrupt Enable
LED2 =0;
while(1)
{
LED1 = 1; //Flash LED1
for(i=0;i<50;i++)
{
}
LED1 = 0;
for(i=0;i<50;i++)
{
}
}
}
void interrupt isr ()
{
INTF = 0; //reset the interrupt flag
LED2 =1; //flip the bit
}
Department of Electrical & Electronics Engineering, Amrita School of Engineering
ADC
ADC module has up to eight analog inputs
Results in 10-bit digital number
Has four registers
A/D Result High Register ADRESH
A/D Result Low Register ADRESL
A/D Control Register0 ADCON0
A/D Control Register1 ADCON1
ADCON0 – controls the operation of the module
ADCON1 – configures the functions of the port pins
Department of Electrical & Electronics Engineering, Amrita School of Engineering
A/D Result Registers • ADRESH:ADRESL is the location of 10-bit A/D result which is 16-
bits wide
• A/D Format select bit ADFM controls the justification to select 10-
bits
Department of Electrical & Electronics Engineering, Amrita School of Engineering
A/D conversion steps
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