fork from github

src/AudioOutputULP.h

@@ -0,0 +1,69 @@
+/*
+  AudioOutputULP
+  Outputs to ESP32 DAC through the ULP, freeing I2S for other uses
+  
+  Copyright (C) 2020  Martin Laclaustra, based on bitluni's code
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+// Instructions:
+// AudioOutputULP out = new AudioOutputULP(); // stereo
+// Connect left channel on pin 25
+// Connect right channel on pin 26
+// OR
+// Connect mono channel on either of them (stereo samples are downmixed)
+// AudioOutputULP out = new AudioOutputULP(1); // mono, only DAC 1
+// OR
+// AudioOutputULP out = new AudioOutputULP(2); // mono, only DAC 2
+
+
+#ifndef _AUDIOOUTPUTULP_H
+#define _AUDIOOUTPUTULP_H
+
+#include "AudioOutput.h"
+
+#ifdef ESP32
+
+class AudioOutputULP : public AudioOutput
+{
+  public:
+    AudioOutputULP(int argActiveDACs=3) {if(argActiveDACs<1||argActiveDACs>2)argActiveDACs=3;activeDACs=argActiveDACs;stereoOutput=activeDACs==3;};
+    ~AudioOutputULP() {};
+    virtual bool begin() override;
+    virtual bool ConsumeSample(int16_t sample[2]) override;
+    virtual bool stop() override;
+    enum : int { DAC1 = 1, DAC2 = 2 };
+  private:
+    int lastFilledWord = 0;
+    uint8_t bufferedOddSample = 128;
+    bool waitingOddSample = true; // must be set to false for mono output
+    int activeDACs = 3; // 1:DAC1; 2:DAC2; 3:both;
+    bool stereoOutput = true;
+    const int opcodeCount = 20;
+    const uint32_t dacTableStart1 = 2048 - 512;
+    const uint32_t dacTableStart2 = dacTableStart1 - 512;
+    uint32_t totalSampleWords = 2048 - 512 - 512 - (opcodeCount + 1); // add 512 for mono
+    const int totalSamples = totalSampleWords * 2;
+    const uint32_t indexAddress = opcodeCount;
+    const uint32_t bufferStart = indexAddress + 1;
+};
+
+#else
+
+#error Only the ESP32 supports ULP audio output
+
+#endif
+
+#endif