- Added test_mixer_routing_output

- Various buffers no longer marked static to allow for easier unit testing 
- Added some comments and removed some dead code from the implementation
- Moved mixer control comms to functions for unit test convenience

tests/test_mixer_routing_output/src/xua_conf.h

@@ -0,0 +1,45 @@
+// Copyright 2016-2022 XMOS LIMITED.
+// This Software is subject to the terms of the XMOS Public Licence: Version 1.
+#ifndef _XUA_CONF_H_
+#define _XUA_CONF_H_
+
+#define NUM_USB_CHAN_OUT        (10)
+#define NUM_USB_CHAN_IN         (10)
+#define I2S_CHANS_DAC           (10)
+#define I2S_CHANS_ADC           (10)
+
+#define EXCLUDE_USB_AUDIO_MAIN
+
+#define MIXER                   (1)
+#define MAX_MIX_COUNT           (8)
+
+#define UAC_FORCE_FEEDBACK_EP   (0)
+#define XUA_NUM_PDM_MICS 0
+#define XUD_TILE 1
+#define AUDIO_IO_TILE 0
+
+#ifndef MCLK_441
+#define MCLK_441 (512 * 44100)
+#endif
+
+#ifndef MCLK_48
+#define MCLK_48 (512 * 48000)
+#endif
+
+#define MIN_FREQ (44100)
+#define MAX_FREQ (192000)
+#define SPDIF_TX_INDEX 0
+#define VENDOR_STR "XMOS"
+#define VENDOR_ID 0x20B1
+#define PRODUCT_STR_A2 "Test device"
+#define PRODUCT_STR_A1 "Test device"
+#define PID_AUDIO_1 1
+#define PID_AUDIO_2 2
+#define AUDIO_CLASS 2
+#define AUDIO_CLASS_FALLBACK 0
+#define BCD_DEVICE 0x1234
+#define XUA_DFU_EN          0
+#define MIC_DUAL_ENABLED 1        //Use single thread, dual PDM mic
+#define XUA_MIC_FRAME_SIZE 240
+
+#endif