Add files via upload

firmware/ltc_audiohat_lock.ino

@@ -0,0 +1,180 @@
+/* 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;
+  }
+}