RP2040 I2S Support

Author: pschatzmann

examples/examples-stream/streams-generator-i2s/streams-generator-i2s.ino

@@ -7,19 +7,19 @@
 
 #include "AudioTools.h"
 
-typedef int16_t sound_t;                                   // sound will be represented as int16_t (with 2 bytes)
 uint16_t sample_rate=44100;
 uint8_t channels = 2;                                      // The stream will have 2 channels 
-SineWaveGenerator<sound_t> sineWave(32000);                // subclass of SoundGenerator with max amplitude of 32000
-GeneratedSoundStream<sound_t> sound(sineWave);             // Stream generated from sine wave
+SineWaveGenerator<int16_t> sineWave(32000);                // subclass of SoundGenerator with max amplitude of 32000
+GeneratedSoundStream<int16_t> sound(sineWave);             // Stream generated from sine wave
 I2SStream out; 
 StreamCopy copier(out, sound);                             // copies sound into i2s
 
 // Arduino Setup
 void setup(void) {  
   // Open Serial 
   Serial.begin(115200);
-  AudioLogger::instance().begin(Serial, AudioLogger::Warning);
+  while(!Serial);
+  AudioLogger::instance().begin(Serial, AudioLogger::Info);
 
   // start I2S
   Serial.println("starting I2S...");

src/AudioConfig.h

@@ -91,6 +91,12 @@
 #ifndef COPY_DELAY_ON_NODATA 
 #define COPY_DELAY_ON_NODATA 10
 #endif
+
+#ifndef COPY_RETRY_LIMIT 
+#define COPY_RETRY_LIMIT 20
+#endif
+
+
 /**
  * ------------------------------------------------------------------------- 
  * @brief PWM

src/AudioI2S/I2SRP2040.h

@@ -33,7 +33,7 @@ class I2SBasePIO {
     }
 
     /// starts the DAC with the default config in TX Mode
-    bool begin(RxTxMode mode = TX_MODE) {
+    bool begin(RxTxMode mode = TX_MODE)  {
       LOGD(LOG_METHOD);
       return begin(defaultConfig(mode));
     }
@@ -58,19 +58,26 @@ class I2SBasePIO {
           LOGE("Unsupported bits_per_sample: %d", cfg.bits_per_sample);
           return false;
       }
-      if (cfg.channels != 2 ){
+
+      if (cfg.channels < 1 || cfg.channels > 2 ){
           LOGE("Unsupported channels: '%d' - only 2 is supported", cfg.channels);
           return false;
       }
-      if (!I2S.begin(cfg.sample_rate)){
+
+      int rate = cfg.sample_rate; 
+      if (cfg.channels==1){
+        rate = rate /2;
+      } 
+
+      if (!I2S.begin(rate)){
           LOGE("Could not start I2S");
           return false;
       }
       return true;
     }
 
     /// stops the I2C and unistalls the driver
-    void end(){
+    void end()  {
       I2S.end();
     }
 
@@ -80,37 +87,80 @@ class I2SBasePIO {
     }
 
     /// writes the data to the I2S interface 
-    size_t writeBytes(const void *src, size_t size_bytes){
+    size_t writeBytes(const void *src, size_t size_bytes)  {
       LOGD(LOG_METHOD);
-      // size_t result = I2S.write(src, frames); 
       size_t result = 0;
-      uint32_t *p32 = (uint32_t *)src;
-      for (int j=0;j<size_bytes/4;j++){
-        while (!I2S.write((void*)p32[j], 4)){
-          delay(5);
-        }
-        result = j*4;
-      }
-      LOGD("%s: %d -> %d ", LOG_METHOD, size_bytes, result);
+      int16_t *p16 = (int16_t *)src;
+      
+      if (cfg.channels==1){
+        int samples = size_bytes/2;
+        // multiply 1 channel into 2
+        int16_t buffer[samples*2]; // from 1 byte to 2 bytes
+        for (int j=0;j<samples;j++){
+          buffer[j*2]= p16[j];
+          buffer[j*2+1]= p16[j];
+        } 
+        result = I2S.write((const uint8_t*)buffer, size_bytes*2)*2;
+      } else if (cfg.channels==2){
+        result = I2S.write((const uint8_t*)src, size_bytes)*4;
+      } 
       return result;
     }
 
-    size_t readBytes(void *dest, size_t size_bytes){
-      LOGD(LOG_METHOD);
+    size_t readBytes(void *dest, size_t size_bytes)  {
+      LOGE(LOG_METHOD);
       size_t result = 0;
       return result;
     }
 
-    virtual int availableForWrite() {
-      return I2S.availableForWrite();
+    int availableForWrite()  {
+      int result = 0;
+      if (cfg.channels == 1){
+        // it should be a multiple of 2
+        result = I2S.availableForWrite()/2*2;
+        // return half of it because we double when writing
+        result = result / 2;
+      } else {
+        // it should be a multiple of 4
+        result = I2S.availableForWrite()/4*4;
+      } 
+      if (result<4){
+        result = 0;
+      }
+      return result;
+    }
+
+    int available()  {
+      return 0;
     }
 
-    int available() {
-      return I2S.available();
+    void flush()   {
+      return I2S.flush();
     }
 
   protected:
     I2SConfig cfg;
+
+    // blocking write
+    void writeSample(int16_t sample){
+        int written = I2S.write(sample);
+        while (!written) {
+          delay(5);
+          LOGW("written: %d ", written);
+          written = I2S.write(sample);
+        }
+    }
+
+    int writeSamples(int samples, int16_t* values){
+        int result=0;
+        for (int j=0;j<samples;j++){
+          int16_t sample = values[j];
+          writeSample(sample);
+          writeSample(sample);
+          result++;
+        }
+        return result;
+    }
 
 };
 

src/AudioTools/AudioCopy.h

@@ -234,7 +234,7 @@ class StreamCopyT {
         void *onWriteObj = nullptr;
         bool is_first = false;
         const char* actual_mime = nullptr;
-        int retryLimit = 20;
+        int retryLimit = COPY_RETRY_LIMIT;
         int delay_on_no_data = COPY_DELAY_ON_NODATA;
 
         // blocking write - until everything is processed

tests/README.md

@@ -1,4 +1,4 @@
 
-In the subdirectories you find the test sketches that can be build on the desktop. 
-For details [see the wiki](https://github.com/pschatzmann/arduino-audio-tools/wiki/Running-an-Audio-Sketch-on-the-Desktop)
+In the subdirectories you find the test sketches that can be built on the desktop. 
+For details [see the Wiki](https://github.com/pschatzmann/arduino-audio-tools/wiki/Running-an-Audio-Sketch-on-the-Desktop)