apps: add Auracast USB sample with LC3 codec

This adds sample that acts as USB sound device. Audio signal is coded
using LC3 and broadacasted using Auracast package.

Author: KKopyscinski

apps/auracast_usb/include/tusb_config.h

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef H_USB_AUDIO_
+#define H_USB_AUDIO_
+
+#include <stdint.h>
+
+typedef void (* usb_audio_sample_rate_cb_t)(uint32_t);
+
+/* Set default sample rate, should only be used before USB is initialized */
+void usb_desc_sample_rate_set(uint32_t sample_rate);
+
+#endif /* H_USB_AUDIO_ */

apps/auracast_usb/include/usb_audio.h

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+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+pkg.name: apps/auracast_usb
+pkg.type: app
+pkg.description: Auracast sample application.
+
+pkg.author: "Krzysztof Kopyściński"
+pkg.email: "[email protected]"
+pkg.homepage: "http://mynewt.apache.org/"
+pkg.keywords:
+
+pkg.deps:
+    - "@apache-mynewt-core/sys/config"
+    - nimble/host
+    - nimble/host/util
+    - nimble/host/services/gap
+    - nimble/host/store/config
+    - "@apache-mynewt-core/kernel/os"
+    - "@apache-mynewt-core/sys/console"
+    - "@apache-mynewt-core/sys/log"
+    - "@apache-mynewt-core/sys/stats"
+    - "@apache-mynewt-core/sys/sysinit"
+    - "@apache-mynewt-core/sys/id"
+    - "@apache-mynewt-core/hw/usb/tinyusb"
+    - "@apache-mynewt-nimble/nimble/host/audio/services/auracast"
+    - "@apache-mynewt-nimble/ext/liblc3"
+    - "@apache-mynewt-nimble/ext/libsamplerate"
+
+pkg.init:
+    audio_usb_init: 402

apps/auracast_usb/pkg.yml

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef H_APP_PRIV_
+#define H_APP_PRIV_
+
+#include <syscfg/syscfg.h>
+
+#ifndef MIN
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+#endif
+
+#define AUDIO_CHANNELS          MYNEWT_VAL(AURACAST_CHAN_NUM)
+#define AUDIO_SAMPLE_SIZE       sizeof(int16_t)
+#define AUDIO_PCM_SAMPLE_RATE   MYNEWT_VAL(USB_AUDIO_OUT_SAMPLE_RATE)
+
+#define LC3_FRAME_DURATION      (MYNEWT_VAL(LC3_FRAME_DURATION))
+#define LC3_SAMPLING_FREQ       (MYNEWT_VAL(LC3_SAMPLING_FREQ))
+#define LC3_BITRATE             (MYNEWT_VAL(LC3_BITRATE))
+#define LC3_FPDT                (LC3_SAMPLING_FREQ * LC3_FRAME_DURATION / 1000000)
+#define BIG_NUM_BIS             (MIN(AUDIO_CHANNELS, MYNEWT_VAL(BIG_NUM_BIS)))
+
+struct chan {
+    void *encoder;
+    uint16_t handle;
+};
+
+extern struct chan chans[AUDIO_CHANNELS];
+#endif /* H_APP_PRIV_ */