PIC18F4550

This is the pin configurations for 40 pins PIC18F4550

PIC18F4550 can use same basic circuit of PIC16F877A. All pins are similar. PGC, PGD, MCLR, VDD, VDD are use for ICSP programming port.

Important  setting in using PIC18F4550

#pragma config PLLDIV = 5 // This value has to be 5 for 20Mhz crystal
#pragma config FOSC   = HSPLL_HS // High Speed oscillator for crystal more than 4Mhz
#define _XTAL_FREQ 16000000 // Use 16Mhz although 20Mhz crystal is used  
   
Although 20Mhz crystal is used , _XTAL_FREQ 16000000 has to be define to be 16Mhz because the speed of this PIC is fix at 4Mhz, 16MHz, 48Mhz...If  _XTAL_FREQ 20000000, __delay_ms() and __delay_us() function is not accurate.  _XTAL_FREQ 16000000 is the only ways I can think to make it accurate.

**If you manage to get accurate delay with _XTAL_FREQ 20000000, please share with me...thanks

18F4550 PIR sensor with LCD display

This project is using PIC18F4550. PIR sensor is used to sense motion. When there is movement, the data pin of PIR sensor will send high signal to PIC. The PIR sensor is very easy to used with PIC as it send digital HIGH and LOW signal only as active HIGH switch. In this project, when there is movement, LCD will shows "object detected" referring to video below.

**PIR sensor needs atleast 5 minutes to be in ready mode. So, delay must be insert before any other program.

Switch controlled LED blinking

Video below shows LED light controlled by forward and reverse switch. When forward button is press, LED will shift to the right and reverse button will make the LED shift to the left. When LED is shifted until the last one, it will back to the first one again.

Programming part

//This is the desired array looks like
unsigned char _options[8]={0b00000001, 0b00000010, 0b00000100, 0b00001000,
  0b00010000, 0b00100000, 0b01000000, 0b10000000};
sel=0;  
PORTD =_options[sel]; //assign PORTD output to follow the array

//this is where button assigned to move forward or reverse
while(1)
{
if(forward==1)
{
if(sel==7) sel=0;
else sel++;
PORTD =_options[sel];
while(forward==1);         //waiting for button to be press
}


else if(reverse==1)
{
if(sel==0) sel=7;
else sel--;
PORTD =_options[sel];
while(reverse==1);
}