This project shows how to decode IR remote controls which uses Philips RC5 protocol with microchip PIC16F84A microcontroller.
You can find details about RC5 on Wikipedia
Related topics:
Philips RC5 & LG TV Remote Control Decoder
IR Remote Control Based On PIC Microcontroller
The RC5 protocols can be divided into 4 parts:
1-start bit,
2-Toggle bit,
3-Address (5 bits),
4-Command (6 bits).
The code:
The code of this project is written using mikroc pro for pic compiler. The crystal used is 12MHz.
//PIC16F84A RC5 Protocol Remote control decoder MikroC code
//http://www.elecnote.blogspot.com
//[email protected]
//Used crystal: 12MHz
//Use at your own risk
// LCD module connections
sbit LCD_RS at RB6_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB4_bit;
sbit LCD_D5 at RB3_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB1_bit;
sbit LCD_RS_Direction at TRISB6_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB3_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB1_bit;
// End LCD module connections
unsigned short ir_read, j, toggle, address=0, command=0;
unsigned char *text, mytext[3];
void Interrupt(){ //External interrupt occured
//Check if the received signal is RC5 protocol
delay_us(370);
if(PORTB.F0==0){
delay_us(889);
if(PORTB.F0==1){
delay_us(889);
if(PORTB.F0==0){
delay_us(1778); ir_read = 1;
INTCON = 0; //Disabe the external interrupt
}}}
INTF_bit = 0; //Clear Interrupt flag
}
//Display the results on 1602 LCD
void display_results (){
Lcd_Cmd(_LCD_CLEAR); //Clear LCD
text = "Tgl:" ;
Lcd_Out(1, 2, text);
text = "Ads:" ;
Lcd_Out(1, 10, text);
text = "Cmd:" ;
Lcd_Out(2, 6, text);
ByteToStr(toggle, mytext); Lcd_Out(1, 6, Ltrim(mytext));
ByteToStr(address, mytext); Lcd_Out(1, 14, Ltrim(mytext));
ByteToStr(command, mytext); Lcd_Out(2, 10, Ltrim(mytext)); }
void main() {
OPTION_REG = 0;
TRISB.F0 = 1;
Lcd_Init();
Lcd_Cmd(_LCD_CURSOR_OFF); // cursor off
Lcd_Cmd(_LCD_CLEAR); // clear LCD
text = "RC5 Decoder" ;
Lcd_Out(1, 3, text);
delay_ms(1000);
INTCON = 0x90; //External Interrupt enabled
while(1){
while(!ir_read); //Wait until IR RC5 protocl received
ir_read = 0;
for(j = 0; j < 12; j++){
if(j == 0){
if (PORTB.F0 == 0) toggle = 1;
else toggle = 0;}
else {
if(j < 6){ //Read address bits
if (PORTB.F0 == 0) address|= (1<<( 5 - j)); //Set bit (5-j)
if (PORTB.F0 == 1) address&=~(1<<(5 - j));} //Clear bit (5-j)
else { //Read command bits
if (PORTB.F0 == 0) command|= (1<<( 11 - j));//Set bit (11-j)
else command&=~(1<<(11 - j)); //Clear bit (11-j)
}}
delay_us(1778);}
display_results(); delay_ms(200);
INTCON = 0x90; //External Interrupt enabled }}
For more detail: RC5 Protocol Remote Control Decoder
