EEVblog · January 25, 2023 20:59 · Aug 12, 2013 · Aug 12, 2013 · Aug 11, 2013
diff --git a/Arduino-IR-TX-NEC b/Arduino-IR-TX-NEC
@@ -4,6 +4,7 @@
 // Assumes an IR LED connected on I/O pin to ground, or equivalent driver.
 // Tested on a Freetronics Eleven Uno compatible
 // Written by David L. Jones www.eevblog.com
+// Youtube video explaining this code: http://www.youtube.com/watch?v=BUvFGTxZBG8
 // License: Creative Commons CC BY
 //*****************************************
 
@@ -26,10 +27,11 @@ void IRsetup(void)
 }
 
 // Ouput the 38KHz carrier frequency for the required time in microseconds
+// This is timing critial and just do-able on an Arduino using the standard I/O functions.
+// If you are using interrupts, ensure they disabled for the duration.
 void IRcarrier(unsigned int IRtimemicroseconds)
 {
-  int i;
-  for(i=0; i < (IRtimemicroseconds / 26); i++)
+  for(int i=0; i < (IRtimemicroseconds / 26); i++)
     {
     digitalWrite(IRLEDpin, HIGH);   //turn on the IR LED
     //NOTE: digitalWrite takes about 3.5us to execute, so we need to factor that into the timing.
@@ -39,7 +41,7 @@ void IRcarrier(unsigned int IRtimemicroseconds)
     }
 }
 
-//Sends the IR code in 
+//Sends the IR code in 4 byte NEC format
 void IRsendCode(unsigned long code)
 {
   //send the leading pulse
@@ -49,21 +51,20 @@ void IRsendCode(unsigned long code)
   //send the user defined 4 byte/32bit code
   for (int i=0; i<32; i++)            //send all 4 bytes or 32 bits
     {
-    IRcarrier(BITtime);        //turn on the carrier for one bit time
-    if (code & 0x80000000)        //get the current bit by masking all but the MSB
-      delayMicroseconds(3 * BITtime);    //a HIGH is 3 bit time periods
+    IRcarrier(BITtime);               //turn on the carrier for one bit time
+    if (code & 0x80000000)            //get the current bit by masking all but the MSB
+      delayMicroseconds(3 * BITtime); //a HIGH is 3 bit time periods
     else
-      delayMicroseconds(BITtime);        //a LOW is only 1 bit time period
+      delayMicroseconds(BITtime);     //a LOW is only 1 bit time period
      code<<=1;                        //shift to the next bit for this byte
     }
-
-  IRcarrier(BITtime);          //send a single STOP bit.
+  IRcarrier(BITtime);                 //send a single STOP bit.
 }
 
-void loop()
+void loop()                           //some demo main code
 {
-  IRsetup();
-  IRsendCode(IRcode);
+  IRsetup();                          //Only need to call this once to setup
+  IRsendCode(IRcode);                 
   delay(5000);
   IRsendCode(IRcode);
   while(1);

diff --git a/Arduino-IR-TX-NEC b/Arduino-IR-TX-NEC
@@ -42,14 +42,12 @@ void IRcarrier(unsigned int IRtimemicroseconds)
 //Sends the IR code in 
 void IRsendCode(unsigned long code)
 {
-  int i;
-  unsigned long c;
   //send the leading pulse
   IRcarrier(9000);            //9ms of carrier
   delayMicroseconds(4500);    //4.5ms of silence
 
   //send the user defined 4 byte/32bit code
-  for (i=0; i<32; i++)            //send all 4 bytes or 32 bits
+  for (int i=0; i<32; i++)            //send all 4 bytes or 32 bits
     {
     IRcarrier(BITtime);        //turn on the carrier for one bit time
     if (code & 0x80000000)        //get the current bit by masking all but the MSB

diff --git a/Arduino-IR-TX-NEC b/Arduino-IR-TX-NEC
@@ -0,0 +1,72 @@
+//*****************************************
+// NEC (Japanese) Infrared code sending library for the Arduino
+// Send a standard NEC 4 byte protocol direct to an IR LED on the define pin
+// Assumes an IR LED connected on I/O pin to ground, or equivalent driver.
+// Tested on a Freetronics Eleven Uno compatible
+// Written by David L. Jones www.eevblog.com
+// License: Creative Commons CC BY
+//*****************************************
+
+#define IRLEDpin  2              //the arduino pin connected to IR LED to ground. HIGH=LED ON
+#define BITtime   562            //length of the carrier bit in microseconds
+//put your own code here - 4 bytes (ADDR1 | ADDR2 | COMMAND1 | COMMAND2)
+unsigned long IRcode=0b11000001110001111100000000111111;  
+
+// SOME CODES:
+// Canon WL-D89 video remote START/STOP button = 0b11000001110001111100000000111111
+
+void setup()
+{
+}
+
+void IRsetup(void)
+{
+  pinMode(IRLEDpin, OUTPUT);
+  digitalWrite(IRLEDpin, LOW);    //turn off IR LED to start
+}
+
+// Ouput the 38KHz carrier frequency for the required time in microseconds
+void IRcarrier(unsigned int IRtimemicroseconds)
+{
+  int i;
+  for(i=0; i < (IRtimemicroseconds / 26); i++)
+    {
+    digitalWrite(IRLEDpin, HIGH);   //turn on the IR LED
+    //NOTE: digitalWrite takes about 3.5us to execute, so we need to factor that into the timing.
+    delayMicroseconds(9);          //delay for 13us (9us + digitalWrite), half the carrier frequnecy
+    digitalWrite(IRLEDpin, LOW);    //turn off the IR LED
+    delayMicroseconds(9);          //delay for 13us (9us + digitalWrite), half the carrier frequnecy
+    }
+}
+
+//Sends the IR code in 
+void IRsendCode(unsigned long code)
+{
+  int i;
+  unsigned long c;
+  //send the leading pulse
+  IRcarrier(9000);            //9ms of carrier
+  delayMicroseconds(4500);    //4.5ms of silence
+
+  //send the user defined 4 byte/32bit code
+  for (i=0; i<32; i++)            //send all 4 bytes or 32 bits
+    {
+    IRcarrier(BITtime);        //turn on the carrier for one bit time
+    if (code & 0x80000000)        //get the current bit by masking all but the MSB
+      delayMicroseconds(3 * BITtime);    //a HIGH is 3 bit time periods
+    else
+      delayMicroseconds(BITtime);        //a LOW is only 1 bit time period
+     code<<=1;                        //shift to the next bit for this byte
+    }
+
+  IRcarrier(BITtime);          //send a single STOP bit.
+}
+
+void loop()
+{
+  IRsetup();
+  IRsendCode(IRcode);
+  delay(5000);
+  IRsendCode(IRcode);
+  while(1);
+}