Send over infrared on Arduino - arduino

Question

I need to transmit an infrared signal using the Arduino to run a Samsung TV.
I tried the following code:
// Lucas Eckels
// Http://lucaseckels.com
// IR remote control emitter for NEC protocol remote, as described at
// Http://www.sbprojects.com/knowledge/ir/nec.htm
// Tested on a Samsung LCD TV.
#include <util/delay.h>
#define IR_PIN 13
// With CONTINOUS defined, the first command is repeated continuously until
// You reset the Arduino. Otherwise, it sends the code once, then waits for
// Another command.
#define CONTINUOUS
// Times are in microseconds
#define ON_START_TIME 4500
#define OFF_START_TIME 4500
#define ON_TIME 580
#define OFF_TIME_ONE 1670
#define OFF_TIME_ZERO 540
#define DEVICE_1 7
#define DEVICE_2 7
void setup() {
pinMode (IR_PIN, OUTPUT);
digitalWrite(IR_PIN, LOW);
Serial.begin(9600);
delay(1000);
Serial.write("Starting up..\n");
}
byte command = 0;
int commandCount = 0;
bool commandReady = false;
void loop() {
if (commandReady) {
Serial.print("Writing command");
Serial.print(command, DEC);
Serial.print("\n");
writeStart();
// Writing device code
writeByte(DEVICE_1);
writeByte(DEVICE_2);
// Writing command code
writeByte(command);
writeByte(~command);
writeEnd();
delay(100);
#ifndef CONTINUOUS
commandReady = false;
command = 0;
commandCount = 0;
#endif
return;
}
if (Serial.available () > 0) {
// Read in a 3-digit decimal command code.
byte incoming = Serial.read();
if (incoming <= '9 ' || incoming >= '0') {
command *= 10;
command += incoming - '0 ';
++commandCount;
}
if (commandCount == 3) {
commandReady = true;
}
}
}
void writeStart() {
modulate(ON_START_TIME);
delayMicroseconds(OFF_START_TIME);
}
void writeEnd() {
modulate(ON_TIME);
}
void writeByte(byte val) {
// Starting with the LSB, write out the
for (int i = 0x01; i & 0xFF; i <<= 1) {
modulate(ON_TIME);
if (val & i) {
delayMicroseconds (OFF_TIME_ONE);
} else {
delayMicroseconds (OFF_TIME_ZERO);
}
}
}
void modulate(int time) {
int count = time / 26;
byte portb = PORTB;
byte portbHigh = portb | 0x20; // Pin 13 is controlled by 0x20 on PORTB.
byte portbLow = portb & ~0x20;
for (int i = 0; i <= count; i++) {
// The ideal version of this loop would be:
// DigitalWrite(IR_PIN, HIGH);
// DelayMicroseconds(13);
// DigitalWrite(IR_PIN, LOW);
// DelayMicroseconds(13);
// But I had a hard time getting the timing to work right. This approach was found
// Through experimentation.
PORTB = portbHigh;
_delay_loop_1(64);
PORTB = portbLow;
_delay_loop_1(64);
}
PORTB = portb;
}
The code compiles but is not working for me.

Answer 1

I wrote this to control an LG TV and Sony Amplifier. You would just need to save your own raw codes to the header file and off you go:
https://github.com/gotnull/SiriProxy-TV-Control/blob/master/arduino-remote/Remote/Remote.pde
// This procedure sends a 38KHz pulse to the IRledPin
// for a certain # of microseconds. We'll use this whenever we need to send codes
void pulseIR(long microsecs) {
// we'll count down from the number of microseconds we are told to wait
cli(); // this turns off any background interrupts
while (microsecs > 0) {
// 38 kHz is about 13 microseconds high and 13 microseconds low
digitalWrite(IRledPin, HIGH); // this takes about 3 microseconds to happen
delayMicroseconds(10); // hang out for 10 microseconds
digitalWrite(IRledPin, LOW); // this also takes about 3 microseconds
delayMicroseconds(10); // hang out for 10 microseconds
// so 26 microseconds altogether
microsecs -= 26;
}
sei(); // this turns them back on
}
I'd also recommend taking a read through Ladyada's wonderful tutorial:
Sensor tutorials - IR remote receiver/decoder tutorial

Answer 2

DelayMicroseconds is fairly accurate, and will be precise enough for your task. However you are right in staying away from DigitalWrite. It takes about 50 times as many clock-cycles to complete compared to direct port assignment (PORTB=... ) which takes exactly one. You will only be able to time a 38MHz pulse that way. I don't know what your _delay_loop_1 does, but everything else seems okay. (aside from the "i + +" but that's a cut'n'paste typo I guess)
Have you checked that it actually lights up? a phone or cheap digicam will actually show you the IR on the screen.