Add Sony Spresense platform support

examples/AMY_Spresense_Test/AMY_Spresense_Test.ino

@@ -0,0 +1,99 @@
+#include <AMY-Arduino.h>
+
+// AMY_Spresense_Analog
+//
+// Minimal AMY example for Sony Spresense analog output.
+// Spresense backend in src/spresense_support.cpp handles DAC output.
+
+void setup() {
+#ifdef LED_BUILTIN
+  pinMode(LED_BUILTIN, OUTPUT);
+  digitalWrite(LED_BUILTIN, HIGH);
+#endif
+
+  Serial.begin(115200);
+  delay(1000);
+  Serial.println("AMY Spresense analog output");
+
+  amy_config_t amy_config = amy_default_config();
+  amy_config.features.startup_bleep = 1;
+  amy_config.features.default_synths = 1;
+
+  // Default synth set may require around 90+ oscillators; keep headroom.
+  amy_config.max_oscs = 128;
+
+  // Use Spresense platform audio path (analog DAC output backend).
+  // To use I2S output instead, uncomment the next line.
+  // amy_config.spresense_output_device = SPRESENSE_OUTPUT_I2S;
+  amy_config.audio = AMY_AUDIO_IS_SPRESENSE;
+  amy_config.midi = AMY_MIDI_IS_NONE;
+
+  amy_start(amy_config);
+
+}
+
+void loop() {
+  amy_update();
+
+  static uint32_t last_ms = 0;
+  uint32_t now = millis();
+  if (now - last_ms > 600) {
+    last_ms = now;
+    static int root = 60;
+    static bool play_chord = false;
+    uint32_t t = amy_sysclock();
+
+    if (!play_chord) {
+      Serial.print("single note ");
+      Serial.print(root);
+      Serial.print(" at ");
+      Serial.println(t);
+
+      amy_event on = amy_default_event();
+      on.time = t;
+      on.synth = 1;
+      on.midi_note = root;
+      on.velocity = 0.8f;
+      amy_add_event(&on);
+
+      amy_event off = amy_default_event();
+      off.time = t + 220;
+      off.synth = 1;
+      off.midi_note = root;
+      off.velocity = 0.0f;
+      amy_add_event(&off);
+    } else {
+      const int chord[3] = {root, root + 4, root + 7};
+      Serial.print("chord ");
+      Serial.print(chord[0]);
+      Serial.print(",");
+      Serial.print(chord[1]);
+      Serial.print(",");
+      Serial.print(chord[2]);
+      Serial.print(" at ");
+      Serial.println(t);
+
+      for (int i = 0; i < 3; ++i) {
+        amy_event on = amy_default_event();
+        on.time = t;
+        on.synth = 1;
+        on.midi_note = chord[i];
+        on.velocity = 0.7f;
+        amy_add_event(&on);
+
+        amy_event off = amy_default_event();
+        off.time = t + 220;
+        off.synth = 1;
+        off.midi_note = chord[i];
+        off.velocity = 0.0f;
+        amy_add_event(&off);
+      }
+    }
+
+    play_chord = !play_chord;
+    root += 2;
+    if (root > 72) {
+      root = 60;
+    }
+  }
+}

library.properties

@@ -6,6 +6,6 @@ sentence=AMY, the Music Synthesizer Library
 paragraph=AMY supports many types of oscillators, filters, envelopes, analog, FM, PCM, Karplus-strong, reverb, chorus, echo
 category=Signal Input/Output
 url=http://github.com/shorepine/amy
-architectures=esp32,stm32,rp2040,mbed_rp2040,rp2350,mbed_rp2350,teensy,STM32F1,STM32F4,STM32H7,nrf52,samd,avr
+architectures=esp32,stm32,rp2040,mbed_rp2040,rp2350,mbed_rp2350,teensy,STM32F1,STM32F4,STM32H7,nrf52,samd,avr,spresense
 includes=AMY-Arduino.h
 depends=

src/amy.c

@@ -48,6 +48,9 @@ uint64_t profile_start_us = 0;
 int64_t amy_get_us() { return esp_timer_get_time(); }
 #elif defined PICO_ON_DEVICE
 int64_t amy_get_us() { return to_us_since_boot(get_absolute_time()); }
+#elif defined(ARDUINO_ARCH_SPRESENSE)
+extern unsigned long micros(void);
+int64_t amy_get_us() { return (int64_t)micros(); }
 #elif defined(_WIN32)
 #ifndef WIN32_LEAN_AND_MEAN
 #define WIN32_LEAN_AND_MEAN

src/amy.h

@@ -72,6 +72,8 @@ extern const uint32_t pcm_wavetable_len;
 
 #ifdef AMY_DAISY
 #define AMY_SAMPLE_RATE 48000
+#elif defined(ARDUINO_ARCH_SPRESENSE)
+#define AMY_SAMPLE_RATE 48000
 #elif defined __EMSCRIPTEN__
 #define AMY_SAMPLE_RATE 48000
 #else
@@ -121,6 +123,8 @@ extern const uint32_t pcm_wavetable_len;
 #define AMY_HAS_REVERB (amy_global.config.features.reverb)
 #define AMY_HAS_AUDIO_IN (amy_global.config.features.audio_in)
 #define AMY_HAS_I2S (amy_global.config.audio == AMY_AUDIO_IS_I2S)
+#define AMY_HAS_SPRESENSE_AUDIO (amy_global.config.audio == AMY_AUDIO_IS_SPRESENSE)
+#define AMY_HAS_PLATFORM_AUDIO_OUT (AMY_HAS_I2S || AMY_HAS_SPRESENSE_AUDIO)
 #define AMY_HAS_DEFAULT_SYNTHS (amy_global.config.features.default_synths)
 #define AMY_HAS_CHORUS (amy_global.config.features.chorus)
 #define AMY_HAS_ECHO (amy_global.config.features.echo)
@@ -313,7 +317,7 @@ typedef int amy_err_t;
 
 #include "amy_fixedpoint.h"
 
-#if defined ARDUINO && !defined TLONG && !defined ESP_PLATFORM
+#if defined ARDUINO && !defined TLONG && !defined ESP_PLATFORM && !defined(ARDUINO_ARCH_SPRESENSE)
 #include "avr/pgmspace.h" // for PROGMEM, DMAMEM, FASTRUN
 #else
 #define PROGMEM 
@@ -634,6 +638,13 @@ typedef struct delay_line {
 #define AMY_AUDIO_IS_I2S 0x01
 #define AMY_AUDIO_IS_USB_GADGET 0x02
 #define AMY_AUDIO_IS_MINIAUDIO 0x04
+#define AMY_AUDIO_IS_SPRESENSE 0x08
+
+#if defined(ARDUINO_ARCH_SPRESENSE)
+// Spresense audio output device selection
+#define SPRESENSE_OUTPUT_ANALOG 0
+#define SPRESENSE_OUTPUT_I2S 1
+#endif
 
 #define AMY_MIDI_IS_NONE 0x0
 #define AMY_MIDI_IS_UART 0x01
@@ -721,6 +732,11 @@ typedef struct  {
     int8_t capture_device_id;
     int8_t playback_device_id;
 
+#if defined(ARDUINO_ARCH_SPRESENSE)
+    // Spresense audio output device (SPRESENSE_OUTPUT_ANALOG or SPRESENSE_OUTPUT_I2S)
+    uint8_t spresense_output_device;
+#endif
+
 } amy_config_t;
 
 typedef struct reverb_state {

src/amy_midi.c

@@ -619,6 +619,14 @@ void stop_midi() {
 }
 #endif
 
+#if defined(ARDUINO_ARCH_SPRESENSE)
+void run_midi() {
+}
+
+void stop_midi() {
+}
+#endif
+
 
 #ifdef __linux__
 void stop_midi() {

src/api.c

@@ -95,6 +95,11 @@ amy_config_t amy_default_config() {
     c.midi_uart = 1; // This is MIDI UART _number_, like index
     #endif
 
+    #if defined(ARDUINO_ARCH_SPRESENSE)
+    c.audio = AMY_AUDIO_IS_SPRESENSE;
+    c.spresense_output_device = SPRESENSE_OUTPUT_ANALOG;  // Default to analog DAC output
+    #endif
+
     return c;
 }
 
@@ -407,7 +412,7 @@ int16_t *amy_update() {
     // Single function to update buffers.
     amy_update_tasks();
     int16_t *block = amy_render_audio();
-    if (AMY_HAS_I2S && !amy_global.i2s_is_in_background) {
+    if (AMY_HAS_PLATFORM_AUDIO_OUT && !amy_global.i2s_is_in_background) {
         amy_i2s_write(
             (uint8_t *)block, AMY_BLOCK_SIZE * AMY_NCHANS * sizeof(int16_t)
         );

src/i2s.c

@@ -5,8 +5,8 @@
 // rp2350, rp2040
 // teensy 3.6, 4.0, 4.1
 
-// Only run this code on MCUs
-#if defined(ESP_PLATFORM) || defined(ARDUINO_ARCH_RP2040) || defined(ARDUINO) || defined(ARDUINO_ARCH_RP2350)
+// Only run this code on MCU targets with platform backends in this file.
+#if defined(ESP_PLATFORM) || defined(ARDUINO_ARCH_RP2040) || defined(ARDUINO_ARCH_RP2350) || defined(ARDUINO_ARCH_SPRESENSE)
 
 #include "amy.h"
 
@@ -574,6 +574,39 @@ void amy_platform_deinit() {
 }
 
 
+#elif defined(ARDUINO_ARCH_SPRESENSE)
+
+// Spresense analog output backend is implemented in C++.
+extern void spresense_setup_audio(amy_config_t *config);
+extern void spresense_teardown_audio(amy_config_t *config);
+extern size_t spresense_audio_write(const uint8_t *buffer, size_t nbytes);
+
+void amy_platform_init() {
+    if (AMY_HAS_SPRESENSE_AUDIO) {
+        spresense_setup_audio(&amy_global.config);
+    }
+}
+
+void amy_platform_deinit() {
+    if (AMY_HAS_SPRESENSE_AUDIO) {
+        spresense_teardown_audio(&amy_global.config);
+    }
+}
+
+void amy_update_tasks() {
+    amy_execute_deltas();
+}
+
+int16_t *amy_render_audio() {
+    amy_render(0, AMY_OSCS, 0);
+    return amy_fill_buffer();
+}
+
+size_t amy_i2s_write(const uint8_t *buffer, size_t nbytes) {
+    return spresense_audio_write(buffer, nbytes);
+}
+
+
 #elif defined __IMXRT1062__