Audio Library for Linear Timecode (LTC)?

[olivierdemoustier]

3.6
As you probably already noticed, I'm not a high level programmer. Still have to learn a lot.
What is the purpose of pin 0 in your example. ( syncpin) i left it unconnected.

[olivierdemoustier]

I have a working code for syncing the input to the output. (like a tentikal) Pulling pin 2 down to ground will set the sync.
Here is my code. (could be written better I think)

/*
Linear Timecode generation and decoding combined

Please modify as needed

(c) Frank B, 2020
(pls keep copyright-info)

To enable decoding:
#define USE_LTC_INPUT
and connect pin1 to pinA2 (=pin 16) !!!! I see no use to do this ????

PIN 2 : if set low it will sync incoming TC to the output TC . Then you can disconnect input TC and output will continue

Licence: MIT
*/
bool insync=0;
int incominghours=0;
int incomingminutes=0;
int incomingseconds=0;
int incomingframes=0;

#define USE_LTC_INPUT //comment-out for generation only
float fps = 25;
const int ltcPin = 1;
const int syncPin = 0;

#include "TimeLib.h"

#ifdef USE_LTC_INPUT
/*
Connect ltc
*/
#include <Audio.h>
#include <analyze_ltc.h>
AudioInputAnalog adc1;
AudioAnalyzeLTC ltc1;
AudioConnection patchCord2(adc1, 0, ltc1, 0);

#else
struct ltcframe_t {
uint64_t data;
uint16_t sync;
};
#endif

IntervalTimer ltcTimer;
IntervalTimer fpsTimer;

volatile int clkCnt = 0;
ltcframe_t ltc;
float ltcTimer_freq;

time_t getTeensy3Time()
{
return Teensy3Clock.get();
}

void genLtc() {
static int state = 0;

if (clkCnt++ >= 2 * 80) {
//ltcTimer.end();
clkCnt = 0;
return;
}

int bitval;
int bitcount = clkCnt / 2;

ltcframe_t ltct;
ltct = ltc;

if (bitcount < 64) {
bitval = (int) (ltct.data >> bitcount) & 0x01;
} else {
bitval = (int) (ltct.sync >> (bitcount - 64)) & 0x01; //backward
}

if ( (bitval == 1) || ( (bitval == 0) && (clkCnt & 0x01) ) == 0) {
state = !state; // toggle state
digitalWriteFast(ltcPin, state);
}

}

//https://www.geeksforgeeks.org/program-to-find-parity/
inline
int getParity(uint64_t n)
{
int parity = 0;
while (n)
{
parity = !parity;
n = n & (n - 1);
}
return parity & 0x01;
}


/*

Gets called by rising edge of syncPin
*/
void startLtc() {

ltcTimer.begin(genLtc, ltcTimer_freq);
ltcTimer.priority(0);

int t, t10;
uint64_t data = ltc.data;
clkCnt = 0;

//get frame number:
t = ((data >> 8) & 0x03) * 10 + (data & 0x0f);

//zero out ltc data, leave d+c flags and user-bits untouched:
data &= 0xf0f0f0f0f0f0fcf0ULL;
//data = 0;
//inc frame-number:
//TODO: realize "drop frame numbering" (when D-Flag is set)
t++;
if (t >= (int) fps) t = 0;
//set frame number:
t10 = t / 10;
data |= (t10 & 0x03) << 8;
data |= ((t - t10 * 10)) << 0;
printTCout();
Serial.printf("%02d\n", t);

//set time:
t = second();
t10 = t / 10;
data |= (t10 & 0x07) << 24; //Seconds tens
data |= ((t - t10 * 10) & 0x0f) << 16;

t = minute();
t10 = t / 10;
data |= (uint64_t)(t10 & 0x07) << 40; //minute tens
data |= (uint64_t)((t - t10 * 10) & 0x0f) << 32;

t = hour();
t10 = t / 10;
data |= (uint64_t)(t10 & 0x03) << 56; //hour tens
data |= (uint64_t)((t - t10 * 10) & 0x0f) << 48;

//set parity:
int parity = (!getParity(data)) & 0x01;
if ((int) fps == 25) {
data |= (uint64_t) parity << 59;
} else {
data |= (uint64_t) parity << 27;
}

ltc.data = data;

}

void initLtcData()
{
ltc.sync = 0xBFFC;
ltc.data = (uint64_t) 0; //<- place your initial data here
}

void genFpsSync() {
static int state = 0;
state = !state; // toggle state
digitalWriteFast(syncPin, state);
}


void setup() {

Serial.begin(115200);
delay(200);
#ifdef USE_LTC_INPUT
AudioMemory(4);
#endif
setSyncProvider(getTeensy3Time);
pinMode(syncPin, OUTPUT);
pinMode(ltcPin, OUTPUT);
pinMode(2, INPUT_PULLUP);
ltcTimer_freq = (1.0f / (2 * 80 * (fps ))) * 1000000.0f - 0.125f;// -0.125: make it a tiny bit faster than needed to allow syncing
initLtcData();
//set frame number to last frame to force roll-over with new second()
ltc.data &= 0xf0f0f0f0f0f0fcf0ULL; //delete all dynamic data in frame
int t, t10;
t = fps;
t10 = t / 10;
ltc.data |= (t10 & 0x03) << 8;
ltc.data |= ((t - t10 * 10));
//now wait for seconds-change
int secs = second();
while (secs == second()) {;}

//start timer and pin-interrupt:
fpsTimer.begin(&genFpsSync, (1.0f / (2 * fps)) * 1000000.0f);
fpsTimer.priority(0);
attachInterrupt(digitalPinToInterrupt(syncPin), &startLtc, RISING);
NVIC_SET_PRIORITY(88, 0); //set GPIO-INT-Priority for Pin 1

}

void loop() {
if (ltc1.available()) {
ltcframe_t ltcframe = ltc1.read();
incominghours=ltc1.hour(&ltcframe);
incomingminutes=ltc1.minute(&ltcframe);
incomingseconds=ltc1.second(&ltcframe);
incomingframes=ltc1.frame(&ltcframe);
Serial.printf("TC in : %02d:%02d:%02d.%02d\n\n", ltc1.hour(&ltcframe), ltc1.minute(&ltcframe), ltc1.second(&ltcframe), ltc1.frame(&ltcframe));
}

bool inpin = digitalRead(2);
if (inpin==0 && insync==0){
if (incomingframes==0){
detachInterrupt(digitalPinToInterrupt(syncPin));
fpsTimer.end();
setTime(incominghours,incomingminutes,incomingseco nds, 01, 01, 2022);
Teensy3Clock.set(now());
ltcTimer_freq = (1.0f / (2 * 80 * (fps ))) * 1000000.0f - 0.125f;// -0.125: make it a tiny bit faster than needed to allow syncing
initLtcData();
//set frame number to last frame to force roll-over with new second()
ltc.data &= 0xf0f0f0f0f0f0fcf0ULL; //delete all dynamic data in frame
int t, t10;
t = fps;
t10 = t / 10;
ltc.data |= (t10 & 0x03) << 8;
ltc.data |= ((t - t10 * 10));
//now wait for seconds-change
int secs = second();
while (secs == second()) {;}
//start timer and pin-interrupt:
fpsTimer.begin(&genFpsSync, (1.0f / (2 * fps)) * 1000000.0f);
fpsTimer.priority(0);
attachInterrupt(digitalPinToInterrupt(syncPin), &startLtc, RISING);
NVIC_SET_PRIORITY(88, 0); //set GPIO-INT-Priority for Pin 1
insync=1;

}
}
}

void printTCout(){
Serial.printf("TCout : %02d:%02d:%02d:", hour(), minute(), second());
}

[BriComp]

/*
Linear Timecode generation and decoding combined

Please modify as needed

(c) Frank B, 2020
(pls keep copyright-info)

To enable decoding:
#define USE_LTC_INPUT
and connect pin1 to pinA2 (=pin 16) !!!! I see no use to do this ????

PIN 2 : if set low it will sync incoming TC to the output TC . Then you can disconnect input TC and output will continue

Licence: MIT
*/
bool insync = 0;
int incominghours = 0;
int incomingminutes = 0;
int incomingseconds = 0;
int incomingframes = 0;

#define USE_LTC_INPUT //comment-out for generation only
float fps = 25;
const int ltcPin = 1;
const int syncPin = 0;

#include "TimeLib.h"

#ifdef USE_LTC_INPUT
/*
Connect ltc
*/
#include <Audio.h>
#include <analyze_ltc.h>
AudioInputAnalog adc1;
AudioAnalyzeLTC ltc1;
AudioConnection patchCord2(adc1, 0, ltc1, 0);

#else
struct ltcframe_t {
	uint64_t data;
	uint16_t sync;
};
#endif

IntervalTimer ltcTimer;
IntervalTimer fpsTimer;

volatile int clkCnt = 0;
ltcframe_t ltc;
float ltcTimer_freq;

time_t getTeensy3Time()
{
	return Teensy3Clock.get();
}

void genLtc() {
	static int state = 0;

	if (clkCnt++ >= 2 * 80) {
		//ltcTimer.end();
		clkCnt = 0;
		return;
	}

	int bitval;
	int bitcount = clkCnt / 2;

	ltcframe_t ltct;
	ltct = ltc;

	if (bitcount < 64) {
		bitval = (int)(ltct.data >> bitcount) & 0x01;
	}
	else {
		bitval = (int)(ltct.sync >> (bitcount - 64)) & 0x01; //backward
	}

	if ((bitval == 1) || ((bitval == 0) && (clkCnt & 0x01)) == 0) {
		state = !state; // toggle state
		digitalWriteFast(ltcPin, state);
	}

}

//https://www.geeksforgeeks.org/program-to-find-parity/
inline
int getParity(uint64_t n)
{
	int parity = 0;
	while (n)
	{
		parity = !parity;
		n = n & (n - 1);
	}
	return parity & 0x01;
}


/*

Gets called by rising edge of syncPin
*/
void startLtc() {

	ltcTimer.begin(genLtc, ltcTimer_freq);
	ltcTimer.priority(0);

	int t, t10;
	uint64_t data = ltc.data;
	clkCnt = 0;

	//get frame number:
	t = ((data >> 8) & 0x03) * 10 + (data & 0x0f);

	//zero out ltc data, leave d+c flags and user-bits untouched:
	data &= 0xf0f0f0f0f0f0fcf0ULL;
	//data = 0;
	//inc frame-number:
	//TODO: realize "drop frame numbering" (when D-Flag is set)
	t++;
	if (t >= (int)fps) t = 0;
	//set frame number:
	t10 = t / 10;
	data |= (t10 & 0x03) << 8;
	data |= ((t - t10 * 10)) << 0;
	printTCout();
	Serial.printf("%02d\n", t);

	//set time:
	t = second();
	t10 = t / 10;
	data |= (t10 & 0x07) << 24; //Seconds tens
	data |= ((t - t10 * 10) & 0x0f) << 16;

	t = minute();
	t10 = t / 10;
	data |= (uint64_t)(t10 & 0x07) << 40; //minute tens
	data |= (uint64_t)((t - t10 * 10) & 0x0f) << 32;

	t = hour();
	t10 = t / 10;
	data |= (uint64_t)(t10 & 0x03) << 56; //hour tens
	data |= (uint64_t)((t - t10 * 10) & 0x0f) << 48;

	//set parity:
	int parity = (!getParity(data)) & 0x01;
	if ((int)fps == 25) {
		data |= (uint64_t)parity << 59;
	}
	else {
		data |= (uint64_t)parity << 27;
	}

	ltc.data = data;

}

void initLtcData()
{
	ltc.sync = 0xBFFC;
	ltc.data = (uint64_t)0; //<- place your initial data here
}

void genFpsSync() {
	static int state = 0;
	state = !state; // toggle state
	digitalWriteFast(syncPin, state);
}


void setup() {

	Serial.begin(115200);
	delay(200);
#ifdef USE_LTC_INPUT
	AudioMemory(4);
#endif
	setSyncProvider(getTeensy3Time);
	pinMode(syncPin, OUTPUT);
	pinMode(ltcPin, OUTPUT);
	pinMode(2, INPUT_PULLUP);
	ltcTimer_freq = (1.0f / (2 * 80 * (fps))) * 1000000.0f - 0.125f;// -0.125: make it a tiny bit faster than needed to allow syncing
	initLtcData();
	//set frame number to last frame to force roll-over with new second()
	ltc.data &= 0xf0f0f0f0f0f0fcf0ULL; //delete all dynamic data in frame
	int t, t10;
	t = fps;
	t10 = t / 10;
	ltc.data |= (t10 & 0x03) << 8;
	ltc.data |= ((t - t10 * 10));
	//now wait for seconds-change
	int secs = second();
	while (secs == second()) { ; }

	//start timer and pin-interrupt:
	fpsTimer.begin(&genFpsSync, (1.0f / (2 * fps)) * 1000000.0f);
	fpsTimer.priority(0);
	attachInterrupt(digitalPinToInterrupt(syncPin), &startLtc, RISING);
	NVIC_SET_PRIORITY(88, 0); //set GPIO-INT-Priority for Pin 1

}

void loop() {
	if (ltc1.available()) {
		ltcframe_t ltcframe = ltc1.read();
		incominghours = ltc1.hour(&ltcframe);
		incomingminutes = ltc1.minute(&ltcframe);
		incomingseconds = ltc1.second(&ltcframe);
		incomingframes = ltc1.frame(&ltcframe);
		Serial.printf("TC in : %02d:%02d:%02d.%02d\n\n", ltc1.hour(&ltcframe), ltc1.minute(&ltcframe), ltc1.second(&ltcframe), ltc1.frame(&ltcframe));
	}

	bool inpin = digitalRead(2);
	if (inpin == 0 && insync == 0) {
		if (incomingframes == 0) {
			detachInterrupt(digitalPinToInterrupt(syncPin));
			fpsTimer.end();
			setTime(incominghours, incomingminutes, incomingseco nds, 01, 01, 2022);
			Teensy3Clock.set(now());
			ltcTimer_freq = (1.0f / (2 * 80 * (fps))) * 1000000.0f - 0.125f;// -0.125: make it a tiny bit faster than needed to allow syncing
			initLtcData();
			//set frame number to last frame to force roll-over with new second()
			ltc.data &= 0xf0f0f0f0f0f0fcf0ULL; //delete all dynamic data in frame
			int t, t10;
			t = fps;
			t10 = t / 10;
			ltc.data |= (t10 & 0x03) << 8;
			ltc.data |= ((t - t10 * 10));
			//now wait for seconds-change
			int secs = second();
			while (secs == second()) { ; }
			//start timer and pin-interrupt:
			fpsTimer.begin(&genFpsSync, (1.0f / (2 * fps)) * 1000000.0f);
			fpsTimer.priority(0);
			attachInterrupt(digitalPinToInterrupt(syncPin), &startLtc, RISING);
			NVIC_SET_PRIORITY(88, 0); //set GPIO-INT-Priority for Pin 1
			insync = 1;

		}
	}
}

void printTCout() {
	Serial.printf("TCout : %02d:%02d:%02d:", hour(), minute(), second());
}

Could you place your code between code tags using the # button.
It makes the code much more readable and therefore more liable to get some help.

[olivierdemoustier]

I'm really new to forums. Could you explain a bit more how to do this? Is it a button somewhere on the forum, or do I add # before I paste the code?

[BriComp]

New to this? You've been a member since Nov 2018.
When making a post, when you want to add some code, press the # button above.
Type or paste your code between the [ CODE][/CODE ] tags generated.
Alternatively type or paste your code, highlight it and then press the # button and your code will have the tags placed before and after your code.

[MarkT]

Is it a button somewhere on the forum

The rightmost button above the text input area.

gives monospaced output like this

[ In "advanced mode" the button is 3rd from the right ]

Hovering above each button explains what it does.

[olivierdemoustier]

I'm using Chrome on a windows10 machine. It does not show these options. (see screenshot) changed to Explorer, it shows them.

[olivierdemoustier]

Has anyone tested this on Teensy 4.0? LTC input is not working for me?

[Frank B]

No, but there is nothing what is model-depended.

[olivierdemoustier]

It really does not work. Maybe Timelib that works different in T4?

[Frank B]

Don't know. Have you tried USB input?

[olivierdemoustier]

Found the solution for T4.0
You need to have the next line in your code.
AudioOutputI2S i2s1;
For T3.6 it is not necessary

[olivierdemoustier]

Found the solution for T4.0
You need to have the next line in your code.
AudioOutputI2S i2s1;
For T3.6 it is not necessary

But this only solves the TC input. TC out still not working on T4.0
I get this message on the serial monitor after compiling.
ADC2_CFG = 00000637

[olivierdemoustier]

Still trying to figure out on how to get this to work on a Teensy4.0, because I need (S)RTC.
So far I found out that it has something to do with the attachInterrupt on the sync pin. That part won't start until I connect a lose wire to the sync-pin. Strange to start with, A pull up resistor will stop the interrupt. But with the loose wire the TC-FRAME rate is going nuts... It will do more then 20 times 25 frames loops per second.....