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180
firmware/ltc_audiohat_lock.ino Normal file
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/* Linear Timecode for Audio Library for Teensy 3.x / 4.x
Copyright (c) 2019, Frank Bösing, f.boesing (at) gmx.de
Development of this audio library was funded by PJRC.COM, LLC by sales of
Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
open source software by purchasing Teensy or other PJRC products.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice, development funding notice, and this permission
notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
/*
https://forum.pjrc.com/threads/41584-Audio-Library-for-Linear-Timecode-(LTC)
LTC example audio at: https://www.youtube.com/watch?v=uzje8fDyrgg
Adapted by Chris Frankland-Wright 2025 for Teensy Audio Shield Input with autodetect FPS for the NTP-TimeTurner Project
*/
#include <Arduino.h>
#include <Audio.h>
#include "analyze_ltc.h"
// —— Configuration ——
// 0.0 → auto-detect; or force 24.0, 25.0, 29.97
const float FORCE_FPS = 0.0f;
// frame-delay compensation (in frames)
const int FRAME_OFFSET = 4;
// how many frame-periods to wait before declaring “lost”
const float LOSS_THRESHOLD_FRAMES = 1.5f;
// Blink periods (ms) for NO_LTC, ACTIVE, LOST
const unsigned long BLINK_PERIOD[3] = { 2000, 100, 500 };
AudioInputI2S i2s1;
AudioAnalyzeLTC ltc1;
AudioControlSGTL5000 sgtl5000;
AudioConnection patchCord(i2s1, 0, ltc1, 0);
enum State { NO_LTC = 0, LTC_ACTIVE, LTC_LOST };
State ltcState = NO_LTC;
bool ledOn = false;
unsigned long lastDecode = 0;
unsigned long lastBlink = 0;
// auto-detect vars
float currentFps = 25.0f;
float periodMs = 0;
const float SMOOTH_ALPHA = 0.1f;
unsigned long lastDetectTs = 0;
// free-run tracking
long freeAbsFrame = 0;
unsigned long lastFreeRun = 0;
void setup() {
Serial.begin(115200);
// while (!Serial);
AudioMemory(12);
sgtl5000.enable();
sgtl5000.inputSelect(AUDIO_INPUT_LINEIN);
pinMode(LED_BUILTIN, OUTPUT);
}
void loop() {
unsigned long now = millis();
// compute dynamic framePeriod (ms) from last known fps
unsigned long framePeriod = (unsigned long)(1000.0f/currentFps + 0.5f);
if (ltc1.available()) {
// —— LOCKED —— read a frame
ltcframe_t frame = ltc1.read();
int h = ltc1.hour(&frame),
m = ltc1.minute(&frame),
s = ltc1.second(&frame),
f = ltc1.frame(&frame);
// —— FPS detect or force ——
if (FORCE_FPS > 0.0f) {
currentFps = FORCE_FPS;
} else {
if (lastDetectTs) {
float dt = now - lastDetectTs;
periodMs = periodMs==0 ? dt : (SMOOTH_ALPHA*dt + (1-SMOOTH_ALPHA)*periodMs);
float measured = 1000.0f/periodMs;
const float choices[3] = {24.0f,25.0f,29.97f};
float bestD=1e6, pick=25.0f;
for (auto c: choices) {
float d = fabs(measured - c);
if (d < bestD) { bestD = d; pick = c; }
}
currentFps = pick;
}
lastDetectTs = now;
}
// —— pack + offset + wrap ——
int nominal = (currentFps>29.5f)?30:int(currentFps+0.5f);
long dayFrames = 24L*3600L*nominal;
long absF = ((long)h*3600 + m*60 + s)*nominal + f + FRAME_OFFSET;
absF = (absF % dayFrames + dayFrames) % dayFrames;
// save for free-run
freeAbsFrame = absF;
lastFreeRun = now;
// unpack for display
long totSec = absF/nominal;
int outF = absF % nominal;
int outS = totSec % 60;
long totMin = totSec/60;
int outM = totMin % 60;
int outH = (totMin/60)%24;
// dynamic drop-frame from bit 10
bool isDF = ltc1.bit10(&frame);
char sep = isDF ? ';' : ':';
// print locked
Serial.printf("[LOCK] %02d:%02d:%02d%c%02d | %.2ffps\r\n",
outH,outM,outS,sep,outF,currentFps);
// update state
ltcState = LTC_ACTIVE;
lastDecode = now;
}
else {
// —— NOT LOCKED —— check if we should switch to free-run
if (ltcState == LTC_ACTIVE) {
// only switch after losing more than LOSS_THRESHOLD_FRAMES
float elapsedFrames = float(now - lastDecode) / float(framePeriod);
if (elapsedFrames >= LOSS_THRESHOLD_FRAMES) {
ltcState = LTC_LOST;
// free-run will begin below
}
}
}
// —— FREE-RUN —— when lost
if (ltcState == LTC_LOST) {
if ((now - lastFreeRun) >= framePeriod) {
freeAbsFrame = (freeAbsFrame + 1) % (24L*3600L*(int)(currentFps+0.5f));
lastFreeRun += framePeriod;
long totSec = freeAbsFrame/((int)(currentFps+0.5f));
int outF = freeAbsFrame % (int)(currentFps+0.5f);
int outS = totSec % 60;
long totMin = totSec/60;
int outM = totMin % 60;
int outH = (totMin/60)%24;
Serial.printf("[FREE] %02d:%02d:%02d:%02d | %.2ffps\r\n",
outH,outM,outS,outF,currentFps);
}
}
// —— LED heartbeat —— non-blocking
unsigned long period = BLINK_PERIOD[ltcState];
if (now - lastBlink >= period/2) {
ledOn = !ledOn;
digitalWrite(LED_BUILTIN, ledOn);
lastBlink = now;
}
}

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firmware/ltc_audiohat_lock_v2.ino Normal file
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/* Linear Timecode for Audio Library for Teensy 3.x / 4.x
Copyright (c) 2019, Frank Bösing, f.boesing (at) gmx.de
Development of this audio library was funded by PJRC.COM, LLC by sales of
Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
open source software by purchasing Teensy or other PJRC products.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice, development funding notice, and this permission
notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
/*
https://forum.pjrc.com/threads/41584-Audio-Library-for-Linear-Timecode-(LTC)
LTC example audio at: https://www.youtube.com/watch?v=uzje8fDyrgg
Adapted by Chris Frankland-Wright 2025 for Teensy Audio Shield Input with autodetect FPS for the NTP-TimeTurner Project
*/
#include <Arduino.h>
#include <Audio.h>
#include "analyze_ltc.h"
// —— Configuration ——
const float FORCE_FPS = 0.0f; // 0 → auto‑detect
const int FRAME_OFFSET = 4; // compensation in frames
const unsigned long LOSS_TIMEOUT = 1000UL; // ms before we go into LOST
const unsigned long BLINK_PERIOD[3] = {2000,100,500}; // NO_LTC, ACTIVE, LOST
AudioInputI2S i2s1;
AudioAnalyzeLTC ltc1;
AudioControlSGTL5000 sgtl5000;
AudioConnection patchCord(i2s1, 0, ltc1, 0);
enum State { NO_LTC=0, LTC_ACTIVE, LTC_LOST };
State ltcState = NO_LTC;
bool ledOn = false;
unsigned long lastDecode = 0;
unsigned long lastBlink = 0;
// FPS detection
float currentFps = 25.0f;
float periodMs = 0;
const float SMOOTH_ALPHA = 0.1f;
unsigned long lastDetectTs = 0;
// free‑run
long freeAbsFrame = 0;
unsigned long lastFreeRun = 0;
void setup() {
Serial.begin(115200);
AudioMemory(12);
sgtl5000.enable();
sgtl5000.inputSelect(AUDIO_INPUT_LINEIN);
pinMode(LED_BUILTIN, OUTPUT);
}
void loop() {
unsigned long now = millis();
// compute framePeriod from currentFps
unsigned long framePeriod = (unsigned long)(1000.0f / currentFps + 0.5f);
// 1) If in ACTIVE and we've gone > LOSS_TIMEOUT w/o decode, enter LOST
if (ltcState == LTC_ACTIVE && (now - lastDecode) >= LOSS_TIMEOUT) {
ltcState = LTC_LOST;
// bump freeAbsFrame by 1 second worth of frames:
int nominal = (currentFps>29.5f) ? 30 : int(currentFps+0.5f);
long dayFrames= 24L*3600L*nominal;
freeAbsFrame = (freeAbsFrame + nominal) % dayFrames;
// reset free‑run timer so we start next tick fresh
lastFreeRun = now;
}
// 2) Handle incoming LTC frame
if (ltc1.available()) {
ltcframe_t frame = ltc1.read();
int h = ltc1.hour(&frame),
m = ltc1.minute(&frame),
s = ltc1.second(&frame),
f = ltc1.frame(&frame);
// — FPS detect or force —
if (FORCE_FPS > 0.0f) {
currentFps = FORCE_FPS;
} else {
if (lastDetectTs) {
float dt = now - lastDetectTs;
periodMs = periodMs==0 ? dt : (SMOOTH_ALPHA*dt + (1-SMOOTH_ALPHA)*periodMs);
float meas = 1000.0f/periodMs;
const float choices[3] = {24.0f,25.0f,29.97f};
float bestD=1e6, pick=25.0f;
for (auto c: choices) {
float d = fabs(meas-c);
if (d < bestD) { bestD=d; pick=c; }
}
currentFps = pick;
}
lastDetectTs = now;
}
// — pack + offset + wrap —
int nominal = (currentFps>29.5f) ? 30 : int(currentFps+0.5f);
long dayFrames = 24L*3600L*nominal;
long absF = ((long)h*3600 + m*60 + s)*nominal + f + FRAME_OFFSET;
absF = (absF % dayFrames + dayFrames) % dayFrames;
// — reset anchors & state —
freeAbsFrame = absF;
lastFreeRun = now;
lastDecode = now;
ltcState = LTC_ACTIVE;
// — print LOCK —
long totSec = absF/nominal;
int outF = absF % nominal;
int outS = totSec % 60;
long totMin = totSec/60;
int outM = totMin % 60;
int outH = (totMin/60) % 24;
bool isDF = ltc1.bit10(&frame);
char sep = isDF?';':':';
Serial.printf("[LOCK] %02d:%02d:%02d%c%02d | %.2ffps\r\n",
outH,outM,outS,sep,outF,currentFps);
// — LED → ACTIVE immediately —
lastBlink = now;
ledOn = true;
digitalWrite(LED_BUILTIN, HIGH);
}
// 3) If in LOST, do free‑run printing
else if (ltcState == LTC_LOST) {
if ((now - lastFreeRun) >= framePeriod) {
freeAbsFrame = (freeAbsFrame + 1) % (24L*3600L*((int)(currentFps+0.5f)));
lastFreeRun += framePeriod;
// — print FREE —
int nominal = (currentFps>29.5f) ? 30 : int(currentFps+0.5f);
long totSec = freeAbsFrame/nominal;
int outF = freeAbsFrame % nominal;
int outS = totSec % 60;
long totMin = totSec/60;
int outM = totMin % 60;
int outH = (totMin/60)%24;
Serial.printf("[FREE] %02d:%02d:%02d:%02d | %.2ffps\r\n",
outH,outM,outS,outF,currentFps);
}
}
// 4) LED heartbeat
unsigned long bp = BLINK_PERIOD[ltcState];
if ((now - lastBlink) >= (bp/2)) {
ledOn = !ledOn;
digitalWrite(LED_BUILTIN, ledOn);
lastBlink = now;
}
}