change to 16khz, add audio filter, refactor to use DMA

baby-mobile-v5.kicad_sch

@@ -2883,6 +2883,12 @@
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@@ -3267,6 +3283,16 @@
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@@ -3547,6 +3583,16 @@
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+		(effects
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+			(justify right bottom)
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@@ -3587,6 +3633,16 @@
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+		(effects
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+			(justify right bottom)
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+	)
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@@ -3727,16 +3783,6 @@
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+				(path "/3033f063-d051-4b2e-89f5-f1cfe4577b32"
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@@ -4205,7 +4319,7 @@
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@@ -4213,7 +4327,7 @@
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baby_mobile_v2/baby_mobile_v2.ino

@@ -149,7 +149,7 @@ const uint8_t BTN_PINS[] = {
 // AUDIO CONFIG
 // ============================================================
 
-#define SAMPLE_RATE       8000
+#define SAMPLE_RATE       16000
 #define AUDIO_BUF_SIZE    512   // larger buffer = fewer SPI transactions
 #define SILENCE           128   // 0x80 = center for unsigned 8-bit
 
@@ -205,10 +205,8 @@ uint32_t g_trackStart[MAX_TRACKS];
 uint32_t g_trackLen[MAX_TRACKS];
 uint8_t  g_currentTrack = 0;
 
-// Audio double-buffer
+// Audio DMA buffers — uint16_t PWM duty-cycle values for EasyDMA
-uint8_t  g_audioBuf[2][AUDIO_BUF_SIZE];
+static uint16_t   g_pwmBuf[2][AUDIO_BUF_SIZE];
-volatile uint8_t  g_activeBuf = 0;
-volatile uint16_t g_bufPos = 0;
 volatile bool     g_bufReady[2] = {false, false};
 uint32_t g_nextReadAddr = 0;
 uint32_t g_playEnd = 0;
@@ -633,6 +631,7 @@ void audioData_write_cb(uint16_t conn_handle, BLECharacteristic* chr,
 }
 
 void setupBLE() {
+    /* Note BLE requires a custom app to communicate, not regular bluetooth */
     Bluefruit.begin();
     Bluefruit.setName("BabyMobile");
     Bluefruit.setTxPower(0);  // 0 dBm — save power, short range is fine
@@ -676,127 +675,155 @@ void setupBLE() {
 
 
 // ============================================================
-// AUDIO PLAYBACK
+// AUDIO PLAYBACK — nRF52840 PWM EasyDMA
 // ============================================================
+//
+// NRF_PWM0 drives the audio pin directly via DMA — no per-sample ISR.
+//   PRESCALER = 0  → 16 MHz base clock
+//   COUNTERTOP = 500 → PWM carrier = 16 MHz / 500 = 32 kHz
+//   SEQ REFRESH = 1  → each sample plays 2 carrier cycles → 16 kHz sample rate
+//
+// Double-buffer: SEQ[0] / SEQ[1] auto-chain via SHORTS.
+// ISR fires only on SEQEND (every 512 samples = 32 ms), sets g_bufReady[b]=false.
+// loop() calls audioFillBuf() to reload the finished buffer.
 
-// nRF52840 has hardware PWM (up to 4 instances, 16MHz base clock)
+#define PWM_COUNTERTOP  500    // 16 MHz / 500 = 32 kHz carrier
-// We use the nrf_pwm peripheral directly for audio output
+#define PWM_SILENCE     250    // midpoint of 0–500 duty-cycle range
-// and a TIMER for the sample rate interrupt.
 
-// For Arduino compatibility, we use analogWrite for the PWM
+// Software gain: 1=unity, 2=2x, etc. Adjustable via 'u'/'d' serial.
-// and a software timer for sample feeding.
-
-// micros() timestamp for next audio sample (loop-driven at 8kHz)
-uint32_t g_nextSampleUs = 0;
-
-// Software gain: 1=unity, 2=2x, etc. (clips at 0/255). Adjustable via 'u'/'d' serial.
 static uint8_t g_audioGain = 1;
 
-// Called from loop() every 125µs while g_playing
+// Read PCM from current source into g_pwmBuf[b], applying gain and scaling.
-void audioTick(void) {
+// Pads the tail with silence if fewer than AUDIO_BUF_SIZE bytes remain.
-    // Output sample with software gain (stretches away from center 128)
+static void audioFillBuf(uint8_t b) {
-    int16_t s = (int16_t)g_audioBuf[g_activeBuf][g_bufPos] - 128;
+    uint8_t pcm[AUDIO_BUF_SIZE];
+    uint32_t toRead = 0;
+    if (g_nextReadAddr < g_playEnd) {
+        toRead = min((uint32_t)AUDIO_BUF_SIZE, g_playEnd - g_nextReadAddr);
+#ifdef POC_INTERNAL_FLASH
+        g_pocFile.read(pcm, toRead);
+#else
+        flashReadBytes(g_nextReadAddr, pcm, toRead);
+#endif
+        g_nextReadAddr += toRead;
+    }
+    for (uint32_t i = 0; i < toRead; i++) {
+        int16_t s = (int16_t)pcm[i] - 128;
         s *= g_audioGain;
         if (s >  127) s =  127;
         if (s < -128) s = -128;
-    analogWrite(PIN_AUDIO_PWM, (uint8_t)(s + 128));
+        g_pwmBuf[b][i] = (uint16_t)((uint8_t)(s + 128)) * PWM_COUNTERTOP / 256;
-    g_bufPos++;
+    }
+    for (uint32_t i = toRead; i < AUDIO_BUF_SIZE; i++) {
+        g_pwmBuf[b][i] = PWM_SILENCE;
+    }
+    g_bufReady[b] = true;
+}
 
-    if (g_bufPos >= AUDIO_BUF_SIZE) {
+// PWM0 ISR — fires every 32 ms (512 samples at 16 kHz).
-        g_bufReady[g_activeBuf] = false;
+// Just signals which buffer needs refilling; loop() does the actual I/O.
-        g_activeBuf ^= 1;
+extern "C" void PWM0_IRQHandler() {
-        g_bufPos = 0;
+    if (NRF_PWM0->EVENTS_SEQEND[0]) {
-
+        NRF_PWM0->EVENTS_SEQEND[0] = 0;
-        if (!g_bufReady[g_activeBuf]) {
+        if (g_playing) {
-            // Buffer underrun — stop cleanly
+            g_bufReady[0] = false;
-            g_playing = false;
+            NRF_PWM0->TASKS_SEQSTART[1] = 1;  // start buf 1 immediately
-            analogWrite(PIN_AUDIO_PWM, SILENCE);
+        }
+    }
+    if (NRF_PWM0->EVENTS_SEQEND[1]) {
+        NRF_PWM0->EVENTS_SEQEND[1] = 0;
+        if (g_playing) {
+            g_bufReady[1] = false;
+            NRF_PWM0->TASKS_SEQSTART[0] = 1;  // start buf 0 immediately
         }
     }
 }
 
 void audioInit() {
-    pinMode(PIN_AUDIO_PWM, OUTPUT);
+    // Silence both DMA buffers
-    analogWrite(PIN_AUDIO_PWM, SILENCE);
+    for (int i = 0; i < AUDIO_BUF_SIZE; i++) {
-    analogWriteResolution(8);  // 8-bit PWM
+        g_pwmBuf[0][i] = PWM_SILENCE;
+        g_pwmBuf[1][i] = PWM_SILENCE;
+    }
+
+    // Configure NRF_PWM0 for EasyDMA sequence mode
+    NRF_PWM0->PSEL.OUT[0] = g_ADigitalPinMap[PIN_AUDIO_PWM];
+    NRF_PWM0->PSEL.OUT[1] = 0x80000000UL;  // disconnected
+    NRF_PWM0->PSEL.OUT[2] = 0x80000000UL;
+    NRF_PWM0->PSEL.OUT[3] = 0x80000000UL;
+    NRF_PWM0->ENABLE      = PWM_ENABLE_ENABLE_Enabled;
+    NRF_PWM0->MODE        = PWM_MODE_UPDOWN_Up;
+    NRF_PWM0->PRESCALER   = PWM_PRESCALER_PRESCALER_DIV_1;  // 16 MHz
+    NRF_PWM0->COUNTERTOP  = PWM_COUNTERTOP;
+    NRF_PWM0->LOOP        = 0;
+    NRF_PWM0->DECODER     = (PWM_DECODER_LOAD_Common       << PWM_DECODER_LOAD_Pos) |
+                             (PWM_DECODER_MODE_RefreshCount << PWM_DECODER_MODE_Pos);
+
+    NRF_PWM0->SEQ[0].PTR      = (uint32_t)g_pwmBuf[0];
+    NRF_PWM0->SEQ[0].CNT      = AUDIO_BUF_SIZE;
+    NRF_PWM0->SEQ[0].REFRESH  = 1;  // each value plays for 2 PWM periods
+    NRF_PWM0->SEQ[0].ENDDELAY = 0;
+    NRF_PWM0->SEQ[1].PTR      = (uint32_t)g_pwmBuf[1];
+    NRF_PWM0->SEQ[1].CNT      = AUDIO_BUF_SIZE;
+    NRF_PWM0->SEQ[1].REFRESH  = 1;
+    NRF_PWM0->SEQ[1].ENDDELAY = 0;
+
+    NRF_PWM0->SHORTS   = 0;  // no auto-shorts; ISR handles sequence chaining
+    NRF_PWM0->INTENSET = PWM_INTENSET_SEQEND0_Msk | PWM_INTENSET_SEQEND1_Msk;
+    NVIC_SetPriority(PWM0_IRQn, 7);
+    NVIC_EnableIRQ(PWM0_IRQn);
+
+    // Start PWM outputting silence (amp is off, so this is silent)
+    NRF_PWM0->TASKS_SEQSTART[0] = 1;
 }
 
 void audioStart(uint8_t trackNum) {
     Serial.print("Playing track ");
-    Serial.print(trackNum);
+    Serial.print(trackNum + 1);
     Serial.print(" of ");
     Serial.println(g_numTracks);
     if (trackNum >= g_numTracks) return;
 
     g_currentTrack = trackNum;
-    g_playEnd = g_trackLen[trackNum];
-    g_nextReadAddr = 0;
 
 #ifdef POC_INTERNAL_FLASH
     if (g_pocFile) g_pocFile.close();
     char fname[16];
     pocFilename(trackNum, fname);
     if (!g_pocFile.open(fname, FILE_O_READ)) {
-        Serial.print("audioStart: cannot open ");
+        Serial.print("audioStart: cannot open "); Serial.println(fname);
-        Serial.println(fname);
         return;
     }
-
+    g_nextReadAddr = 0;
-    // Pre-fill buf 0
+    g_playEnd = g_trackLen[trackNum];
-    uint32_t toRead = min((uint32_t)AUDIO_BUF_SIZE, g_playEnd - g_nextReadAddr);
-    g_pocFile.read(g_audioBuf[0], toRead);
-    g_nextReadAddr += toRead;
-    g_bufReady[0] = true;
-
-    // Pre-fill buf 1
-    if (g_nextReadAddr < g_playEnd) {
-        toRead = min((uint32_t)AUDIO_BUF_SIZE, g_playEnd - g_nextReadAddr);
-        g_pocFile.read(g_audioBuf[1], toRead);
-        g_nextReadAddr += toRead;
-        g_bufReady[1] = true;
-    } else {
-        memset(g_audioBuf[1], SILENCE, AUDIO_BUF_SIZE);
-        g_bufReady[1] = true;
-    }
 #else
-    uint32_t start = g_trackStart[trackNum];
+    g_nextReadAddr = g_trackStart[trackNum];
-    g_playEnd = start + g_trackLen[trackNum];
+    g_playEnd = g_nextReadAddr + g_trackLen[trackNum];
-    g_nextReadAddr = start;
-
-    // Pre-fill both buffers
-    uint32_t toRead = min((uint32_t)AUDIO_BUF_SIZE, g_playEnd - g_nextReadAddr);
-    flashReadBytes(g_nextReadAddr, g_audioBuf[0], toRead);
-    g_nextReadAddr += toRead;
-    g_bufReady[0] = true;
-
-    if (g_nextReadAddr < g_playEnd) {
-        toRead = min((uint32_t)AUDIO_BUF_SIZE, g_playEnd - g_nextReadAddr);
-        flashReadBytes(g_nextReadAddr, g_audioBuf[1], toRead);
-        g_nextReadAddr += toRead;
-        g_bufReady[1] = true;
-    } else {
-        memset(g_audioBuf[1], SILENCE, AUDIO_BUF_SIZE);
-        g_bufReady[1] = true;
-    }
 #endif
 
-    g_activeBuf = 0;
+    // Stop DMA cleanly, fill both buffers, restart
-    g_bufPos = 0;
+    NRF_PWM0->TASKS_STOP = 1;
+    uint32_t t = millis();
+    while (!NRF_PWM0->EVENTS_STOPPED && millis() - t < 10) {}
+    NRF_PWM0->EVENTS_STOPPED = 0;
+
+    audioFillBuf(0);
+    audioFillBuf(1);
+
+    NRF_PWM0->SEQ[0].PTR = (uint32_t)g_pwmBuf[0];
+    NRF_PWM0->SEQ[1].PTR = (uint32_t)g_pwmBuf[1];
 
     // Enable amplifier
     digitalWrite(PIN_AMP_SD, HIGH);
     delay(10);
 
     g_playing = true;
-    g_nextSampleUs = micros();
+    NRF_PWM0->TASKS_SEQSTART[0] = 1;
-
-    Serial.print("Playing track ");
-    Serial.println(trackNum + 1);
 }
 
 void audioStop() {
     g_playing = false;
-    analogWrite(PIN_AUDIO_PWM, SILENCE);
+    NRF_PWM0->TASKS_STOP = 1;
 
 #ifdef POC_INTERNAL_FLASH
     if (g_pocFile) g_pocFile.close();
@@ -804,7 +831,6 @@ void audioStop() {
 
     // Disable amp
     digitalWrite(PIN_AMP_SD, LOW);
-
     Serial.println("Playback stopped");
 }
 
@@ -856,16 +882,7 @@ uint8_t buttonRead() {
 
 void waitButtonRelease(uint8_t btn) {
     unsigned long deadline = millis() + 300;
-    while (buttonRead() == btn && millis() < deadline) {
+    while (buttonRead() == btn && millis() < deadline) {}
-        // Keep audio running while waiting for button release
-        if (g_playing) {
-            uint32_t now = micros();
-            if ((int32_t)(now - g_nextSampleUs) >= 0) {
-                g_nextSampleUs += 125;
-                audioTick();
-            }
-        }
-    }
 }
 
 
@@ -982,59 +999,14 @@ void setup() {
     audioInit();
 
 #ifdef POC_INTERNAL_FLASH
-    // Boot test tone: 440Hz square wave for 1 second
-    // If you hear a beep, the amp/PWM chain is working.
-    Serial.println("Boot tone disabled...");
-    // digitalWrite(PIN_AMP_SD, HIGH);
-    delay(20);
-    for (int i = 0; i < 8000; i++) {
-        // 440Hz at 8kHz sample rate: 8000/440 ≈ 18 samples/cycle
-        analogWrite(PIN_AUDIO_PWM, (i % 18) < 9 ? 255 : 0);
-        delayMicroseconds(125);
-    }
-    analogWrite(PIN_AUDIO_PWM, SILENCE);
-    delay(20);
-    digitalWrite(PIN_AMP_SD, LOW);
-    Serial.println("Boot tone done");
-
-    // Hex dump track 0 + blocking playback diagnostic
-    // (after audioInit so amp/PWM are ready)
     if (g_numTracks > 0) {
-        char diagName[16]; pocFilename(0, diagName);
+        Serial.println("Diag: playing track0 for 3s...");
-        File diagF(InternalFS);
-        if (diagF.open(diagName, FILE_O_READ)) {
-            uint32_t fsz = diagF.size();
-            Serial.print("Track0 size: "); Serial.println(fsz);
-            uint8_t hbuf[64];
-            int nr = diagF.read(hbuf, sizeof(hbuf));
-            diagF.close();
-            Serial.print("First "); Serial.print(nr); Serial.println(" bytes (hex):");
-            for (int i = 0; i < nr; i++) {
-                if (hbuf[i] < 0x10) Serial.print("0");
-                Serial.print(hbuf[i], HEX);
-                Serial.print(i % 16 == 15 ? "\n" : " ");
-            }
-            Serial.println();
-        } else {
-            Serial.println("Cannot open track0 for read!");
-        }
-
-        Serial.println("Diag: blocking play track0 for 3s...");
         audioStart(0);
         uint32_t diagEnd = millis() + 3000;
         while (millis() < diagEnd && g_playing) {
-            uint32_t now = micros();
-            if ((int32_t)(now - g_nextSampleUs) >= 0) {
-                g_nextSampleUs += 125;
-                audioTick();
-            }
             for (uint8_t b = 0; b < 2; b++) {
                 if (!g_bufReady[b] && g_nextReadAddr < g_playEnd) {
-                    uint32_t toRead = min((uint32_t)AUDIO_BUF_SIZE, g_playEnd - g_nextReadAddr);
+                    audioFillBuf(b);
-                    g_pocFile.read(g_audioBuf[b], toRead);
-                    for (uint32_t i = toRead; i < AUDIO_BUF_SIZE; i++) g_audioBuf[b][i] = SILENCE;
-                    g_nextReadAddr += toRead;
-                    g_bufReady[b] = true;
                 }
             }
         }
@@ -1212,43 +1184,22 @@ static void serUploadTick() {
 #endif
 
 void loop() {
-    // ---- Audio sample output (8kHz, loop-driven) ----
+    if (g_playing) g_lastActivity = millis();
-    if (g_playing) {
-        g_lastActivity = millis();  // stay awake while audio is playing
-        uint32_t now = micros();
-        if ((int32_t)(now - g_nextSampleUs) >= 0) {
-            g_nextSampleUs += 125;  // 1/8000s = 125µs
-            audioTick();
-        }
-    }
 
     // ---- Serial upload (POC mode) ----
 #ifdef POC_INTERNAL_FLASH
     serUploadTick();
 #endif
 
-    // ---- Refill audio buffers ----
+    // ---- Refill audio buffers (ISR sets g_bufReady[b]=false when buffer done) ----
     if (g_playing) {
         for (uint8_t b = 0; b < 2; b++) {
             if (!g_bufReady[b] && g_nextReadAddr < g_playEnd) {
-                uint32_t remaining = g_playEnd - g_nextReadAddr;
+                audioFillBuf(b);
-                uint32_t toRead = min((uint32_t)AUDIO_BUF_SIZE, remaining);
-
-#ifdef POC_INTERNAL_FLASH
-                g_pocFile.read(g_audioBuf[b], toRead);
-#else
-                flashReadBytes(g_nextReadAddr, g_audioBuf[b], toRead);
-#endif
-                // Pad with silence
-                for (uint32_t i = toRead; i < AUDIO_BUF_SIZE; i++) {
-                    g_audioBuf[b][i] = SILENCE;
-                }
-                g_nextReadAddr += toRead;
-                g_bufReady[b] = true;
             }
         }
 
-        // Track finished? Auto-advance and loop
+        // Track finished — both buffers drained and no data left
         if (!g_bufReady[0] && !g_bufReady[1] && g_nextReadAddr >= g_playEnd) {
             audioStop();
             if (g_numTracks > 0) {

baby_mobile_v2/upload_track.py

@@ -44,12 +44,12 @@ def convert_to_pcm(path: str) -> bytes:
                 sample_rate   = struct.unpack_from("<I", data, 24)[0]
                 bits_per_samp = struct.unpack_from("<H", data, 34)[0]
                 needs_convert = (audio_format != 1 or num_channels != 1
-                                 or sample_rate != 8000 or bits_per_samp != 8)
+                                 or sample_rate != 16000 or bits_per_samp != 8)
             except Exception:
                 needs_convert = True
 
             if not needs_convert:
-                print("WAV is already 8-bit mono 8kHz — stripping header")
+                print("WAV is already 8-bit mono 16kHz — stripping header")
                 return data[44:]
             print("WAV needs resampling — converting via ffmpeg")
         # fall through to ffmpeg conversion
@@ -64,14 +64,14 @@ def convert_to_pcm(path: str) -> bytes:
     print(f"Converting {os.path.basename(path)} via ffmpeg...")
     result = subprocess.run(
         ['ffmpeg', '-y', '-i', path,
-         '-ar', '8000', '-ac', '1', '-f', 'u8', '-acodec', 'pcm_u8', 'pipe:1'],
+         '-ar', '16000', '-ac', '1', '-f', 'u8', '-acodec', 'pcm_u8', 'pipe:1'],
         capture_output=True
     )
     if result.returncode != 0:
         sys.exit(f"ERROR: ffmpeg failed:\n{result.stderr.decode(errors='replace')[-400:]}")
 
     pcm = result.stdout
-    duration = len(pcm) / 8000
+    duration = len(pcm) / 16000
     print(f"  Converted: {len(pcm):,} bytes ({duration:.1f}s)")
     return pcm
 
@@ -133,10 +133,10 @@ def upload(port: str, track_num: int, pcm: bytes) -> None:
             if "at=" in err_line:
                 accepted = int(err_line.split("at=")[1].split()[0])
                 safe = int(accepted * 0.9)  # 10% headroom
-                max_s = safe / 8000
+                max_s = safe / 16000
                 print(f"  LittleFS accepted {accepted} bytes before full.")
                 print(f"  Safe clip length: ~{max_s:.1f}s")
-                print(f"  Trim with:  ffmpeg -i input.mp3 -t {max_s:.0f} -ar 8000 -ac 1 -f u8 out.raw")
+                print(f"  Trim with:  ffmpeg -i input.mp3 -t {max_s:.0f} -ar 16000 -ac 1 -f u8 out.raw")
             sys.exit(1)
 
         # Wait for OK