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tunatopraktan
Joined: 19 Mar 2021
Posts: 13
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| 38kHz IR signal transmitter |
 Posted: Thu Apr 15, 2021 1:59 pm |
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38kHz IR signal transmitter
Hello friends.
I am working on a IR signal circuit. I want to control my Samsung TV. But i am confused.
I have a 20mHz external crystal. How will i create 38kHz carrier signal ?
There are a few examples with internal oscillator. But as i said, i will use external 20Mhz crystal.
Thank you. |
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temtronic
Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario
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| Posted: Thu Apr 15, 2021 2:45 pm |
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How ??
There are several ways but we need to know which PIC you have to use.
Depending on the PIC, there are different internal peripherals that can be used.
Also you'll need to know how to 'pulse' the 38KHz signal to 'mimic' the pushbuttons on the remote. |
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tunatopraktan
Joined: 19 Mar 2021
Posts: 13
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| Posted: Thu Apr 15, 2021 2:55 pm |
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| temtronic wrote: | How ??
There are several ways but we need to know which PIC you have to use.
Depending on the PIC, there are different internal peripherals that can be used.
Also you'll need to know how to 'pulse' the 38KHz signal to 'mimic' the pushbuttons on the remote. |
Hello,
I will use pic16F877A.
I have learned remote codes with my receiver circuit. volume up code, volume down code, etc...
I plan to use pwm out to send signals.
There is a sample code below.
But, i want to use external 20Mhz crystal.
| Code: |
#include <12F1822.h>
#fuses NOMCLR INTRC_IO PLL_SW
#use delay(clock=32000000)
#use fast_io(A)
#use pwm (PWM1, FREQUENCY = 38KHz, DUTY = 25, PWM_OFF)
void send_signal(unsigned int32 number){
int8 i;
// Send 9ms burst
pwm_on();
delay_ms(9);
// Send 4.5ms space
pwm_off();
delay_us(4500);
// Send data
for(i = 0; i < 32; i++){
// If bit is 1 send 560us pulse and 1680us space
if(bit_test(number, 31 - i)){
pwm_on();
delay_us(560);
pwm_off();
delay_us(1680);
}
// If bit is 0 send 560us pulse and 560us space
else{
pwm_on();
delay_us(560);
pwm_off();
delay_us(560);
}
}
// Send end bit
pwm_on();
delay_us(560);
pwm_off();
delay_us(560);
}
void main() {
setup_oscillator(OSC_8MHZ | OSC_PLL_ON); // Set internal oscillator to 32MHz (8MHz and PLL)
output_a(0);
set_tris_a(0x3B); // Configure RA2 pin as output and others as inputs
port_a_pullups(0x3B); // Enable internal pull-ups for pins RA0,RA1,RA3,RA4 & RA5
while(TRUE){
while(!input(PIN_A0)){
send_signal(0x40BF00FF);
delay_ms(500);
}
while(!input(PIN_A1)){
send_signal(0x40BF807F);
delay_ms(500);
}
while(!input(PIN_A3)){
send_signal(0x40BF40BF);
delay_ms(500);
}
while(!input(PIN_A4)){
send_signal(0x40BF20DF);
delay_ms(500);
}
while(!input(PIN_A5)){
send_signal(0x40BFA05F);
delay_ms(500);
}
}
} |
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