text: // Copyright 2015 Emilie Gillet.
  //
  // Author: Emilie Gillet (emilie.o.gillet@gmail.com)
  //
  // 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 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.
  // 
  // See http://creativecommons.org/licenses/MIT/ for more information.
  //
  // -----------------------------------------------------------------------------
  //
  // Driver for quad SPI DAC.
  
  #ifndef MARBLES_DRIVERS_DAC_H_
  #define MARBLES_DRIVERS_DAC_H_
  
  #include "stmlib/stmlib.h"
  
  #include <stm32f4xx_conf.h>
  
  #include "marbles/io_buffer.h"
  
  namespace marbles {
  
  enum DacChannel {
    DAC_CHANNEL_X_1,
    DAC_CHANNEL_X_2,
    DAC_CHANNEL_X_3,
    DAC_CHANNEL_Y,
    DAC_CHANNEL_LAST
  };
  
  const size_t kMaxDacBlockSize = 8;
  const size_t kNumDacChannels = 4;
  
  class Dac {
   public:
    Dac() { }
    ~Dac() { }
    
    typedef IOBuffer::Slice (*FillBufferCallback)(size_t size);
    
    void Init(int sample_rate, size_t block_size);
    void Start(FillBufferCallback callback);
    void Stop();
    void Fill(size_t offset);
    
    static Dac* GetInstance() { return instance_; }
    
   private:
    void InitializeGPIO();
    void InitializeAudioInterface(int sample_rate);
    void InitializeDMA(size_t block_size);
    static Dac* instance_;
    
    size_t block_size_;
    FillBufferCallback callback_;
    
    // There are 8 16-bit words per frame.
    uint16_t tx_dma_buffer_[2 * kMaxDacBlockSize * kNumDacChannels * 2];
  
    DISALLOW_COPY_AND_ASSIGN(Dac);
  };
  
  }  // namespace marbles
  
  #endif  // MARBLES_DRIVERS_DAC_H_
  