diff --git a/src/btstack_sco_transport.h b/src/btstack_sco_transport.h
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+/*
+ * Copyright (C) 2021 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,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * Please inquire about commercial licensing options at
+ * contact@bluekitchen-gmbh.com
+ *
+ */
+
+/*
+ * btstack_sco_transport.h
+ * Hardware abstraction for PCM/I2S Inteface used for HSP/HFP profiles
+ */
+
+#ifndef BTSTACK_SCO_TRANSPORT_H
+#define BTSTACK_SCO_TRANSPORT_H
+
+#include "btstack_config.h"
+
+#include "bluetooth.h"
+#include "btstack_defines.h"
+
+#include <stdint.h>
+
+#if defined __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+    SCO_FORMAT_8_BIT,
+    SCO_FORMAT_16_BIT,
+} sco_format_t;
+
+typedef struct {
+
+    /**
+     * register packet handler for SCO HCI packets
+     */
+    void (*register_packet_handler)(void (*handler)(uint8_t packet_type, uint8_t *packet, uint16_t size));
+
+    /**
+     * open transport
+     * @param con_handle of SCO connection
+     * @param sco_format
+     */
+    void (*open)(hci_con_handle_t con_handle, sco_format_t sco_format);
+
+    /**
+     * send SCO packet
+     */
+    void (*send_packet)(const uint8_t *buffer, uint16_t length);
+
+    /**
+     * close transport
+     * @param con_handle of SCO connection
+     */
+    void (*close)(hci_con_handle_t con_handle);
+
+} btstack_sco_transport_t;
+
+#if defined __cplusplus
+}
+#endif
+
+#endif
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