gistfile1.c

/*
Send a Start/Sop Recording command to the LANC port of a video camera.
Tested with a Canon XF300 camcorder
This code requires a simple interface see http://micro.arocholl.com
Feel free to use this code in any way you want.

Comprehensive LANC info: www.boehmel.de/lanc.htm

"LANC" is a registered trademark of SONY.
CANON calls their LANC compatible port "REMOTE".

2011, Martin Koch
http://controlyourcamera.blogspot.com/2011/02/arduino-controlled-video-recording-over.html
*/

#define cmdPin 7 
#define lancPin 11
#define recButton 2
int cmdRepeatCount;
int bitDuration = 104; //Duration of one LANC bit in microseconds. 

void setup() {

pinMode(lancPin, INPUT); //listens to the LANC line
pinMode(cmdPin, OUTPUT); //writes to the LANC line
pinMode(recButton, INPUT); //start-stop recording button
digitalWrite(recButton, HIGH); //turn on an internal pull up resistor
digitalWrite(cmdPin, LOW); //set LANC line to +5V
delay(5000); //Wait for camera to power up completly
bitDuration = bitDuration - 8; //Writing to the digital port takes about 8 microseconds so only 96 microseconds are left till the end of each bit
}

void loop() {
if (!digitalRead(recButton)) {
REC(); //send REC command to camera
delay(1000); //debounce button
}
}



void REC() {

cmdRepeatCount = 0;

while (cmdRepeatCount < 5) {  //repeat 5 times to make sure the camera accepts the command

                while (pulseIn(lancPin, HIGH) < 5000) {   
                  //"pulseIn, HIGH" catches any 0V TO +5V TRANSITION and waits until the LANC line goes back to 0V 
                  //"pulseIn" also returns the pulse duration so we can check if the previous +5V duration was long enough (>5ms) to be the pause before a new 8 byte data packet
//Loop till pulse duration is >5ms
}

//LOW after long pause means the START bit of Byte 0 is here
delayMicroseconds(bitDuration);  //wait START bit duration

//Write the 8 bits of byte 0 
//"18hex" or “00011000”  tells the camera that there will be a normal command to camera in the next byte
//Note that the command bits have to be put out in reverse order with the least significant, right-most bit (bit 0) first
digitalWrite(cmdPin, LOW);  //Write bit 0. 
delayMicroseconds(bitDuration); 
digitalWrite(cmdPin, LOW);  //Write bit 1 
delayMicroseconds(bitDuration);  
digitalWrite(cmdPin, LOW);  //Write bit 2
delayMicroseconds(bitDuration); 
digitalWrite(cmdPin, HIGH);  //Write bit 3
delayMicroseconds(bitDuration);  
digitalWrite(cmdPin, HIGH);  //Write bit 4
delayMicroseconds(bitDuration);
digitalWrite(cmdPin, LOW);  //Write bit 5 
delayMicroseconds(bitDuration);
digitalWrite(cmdPin, LOW);  //Write bit 6
delayMicroseconds(bitDuration); 
digitalWrite(cmdPin, LOW);  //Write bit 7
delayMicroseconds(bitDuration);
//Byte 0 is written now put LANC line back to +5V
digitalWrite(cmdPin, LOW);
delayMicroseconds(10); //make sure to be in the stop bit before byte 1

while (digitalRead(lancPin)) { 
//Loop as long as the LANC line is +5V during the stop bit
}

//0V after the previous stop bit means the START bit of Byte 1 is here
delayMicroseconds(bitDuration);  //wait START bit duration

//Write the 8 bits of Byte 1
//"33hex" or “00110011” sends the  Record Start/Stop command
//Note that the command bits have to be put out in reverse order with the least significant, right-most bit (bit 0) first
digitalWrite(cmdPin, HIGH);  //Write bit 0 
delayMicroseconds(bitDuration);
digitalWrite(cmdPin, HIGH);  //Write bit 1 
delayMicroseconds(bitDuration); 
digitalWrite(cmdPin, LOW);  //Write bit 2
delayMicroseconds(bitDuration); 
digitalWrite(cmdPin, LOW);  //Write bit 3
delayMicroseconds(bitDuration);
digitalWrite(cmdPin, HIGH);  //Write bit 4 
delayMicroseconds(bitDuration); 
digitalWrite(cmdPin, HIGH);  //Write bit 5
delayMicroseconds(bitDuration);
digitalWrite(cmdPin, LOW);  //Write bit 6
delayMicroseconds(bitDuration);
digitalWrite(cmdPin, LOW);  //Write bit 7
delayMicroseconds(bitDuration);
//Byte 1 is written now put LANC line back to +5V
digitalWrite(cmdPin, LOW); 

cmdRepeatCount++;  //increase repeat count by 1

/*Control bytes 0 and 1 are written, now don’t care what happens in Bytes 2 to 7
and just wait for the next start bit after a long pause to send the first two command bytes again.*/


}//While cmdRepeatCount < 5
}