Introduce review hal_audio for playback/recording using circular buffer set

platform/embedded/hal_audio.h

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+/*
+ * Copyright (C) 2018 BlueKitchen GmbH
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holders nor the names of
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ * 4. Any redistribution, use, or modification is done solely for
+ *    personal benefit and not for any commercial purpose or for
+ *    monetary gain.
+ *
+ * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
+ * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
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+ */
+
+#ifndef __HAL_AUDIO_H
+#define __HAL_AUDIO_H
+
+#include <stdint.h>
+
+/*
+ *  hal_audio.h
+ *
+ *  Hardware abstraction layer that provides circular audio playback and recording
+ *
+ *  Assumptions: 
+ *  - num buffers n >= 2
+ *  - after start, buffers are played in sequence 0, 1, ... , n-1, 0, 1, .. , n-1, ... 
+ *  - after a buffer is played, the callback is called with tbe index of the played buffer
+ */
+
+/**
+ * @brief Setup audio codec for specified samplerate and number channels
+ * @param Channels
+ * @param Sample rate
+ * @param Buffer played callback
+ * @param Buffer recorded callback (use NULL if no recording)
+ */
+void hal_audio_init(uint8_t channels, 
+                    uint32_t sample_rate,
+                    void (*buffer_played_callback)  (uint8_t buffer_index),
+                    void (*buffer_recorded_callback)(const int16_t * buffer, uint16_t num_samples));
+
+/**
+ * @brief Get number of output buffers in HAL
+ * @returns num buffers
+ */
+uint16_t hal_audio_get_num_output_buffers(void);
+
+/**
+ * @brief Get size of single output buffer in HAL
+ * @returns buffer size
+ */
+uint16_t hal_audio_get_num_output_buffer_samples(void);
+
+/**
+ * @brief Gey output buffer
+ * @param buffer index
+ * @returns buffer
+ */
+int16_t * hal_audio_get_output_buffer(uint8_t buffer_index);
+
+/**
+ * @brief Start stream
+ */
+void hal_audio_start(void);
+
+/**
+ * @brief Close audio codec
+ */
+void hal_audio_close(void);
+
+#endif