Trial add of PDM code

module_usb_audio/pcm_pdm_mic.xc

@@ -0,0 +1,103 @@
+#include <xscope.h>
+#include <platform.h>
+#include <xs1.h>
+#include <stdlib.h>
+#include "beam.h"
+#include <print.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "static_constants.h"
+#if 1
+on tile[0]: in port p_pdm_clk = XS1_PORT_1E;
+on tile[0]: in buffered port:8 p_pdm_mics = XS1_PORT_8B;
+in port p_mclk                 = on tile[0]: XS1_PORT_1F;
+clock mclk                     = on tile[0]: XS1_CLKBLK_1;
+clock pdmclk                   = on tile[0]: XS1_CLKBLK_3;
+
+in port p_buttons = on tile[0]: XS1_PORT_4C;
+
+typedef struct {
+    unsigned ch_a;
+    unsigned ch_b;
+} double_packed_audio;
+
+typedef struct {
+    double_packed_audio data[4][1<<FRAME_SIZE_LOG2];
+} synchronised_audio;
+
+
+void example(streaming chanend c_ds_output_0, streaming chanend c_ds_output_1, streaming chanend c_pcm_out)
+{
+
+
+    unsigned buffer = 1;            //buffer index
+    synchronised_audio audio[2];    //double buffered
+    memset(audio, sizeof(synchronised_audio), 2);
+
+
+    unsafe
+    {
+        c_ds_output_0 <: (synchronised_audio * unsafe)audio[0].data[0];
+        c_ds_output_1 <: (synchronised_audio * unsafe)audio[0].data[2];
+
+        while(1)
+        {   
+
+            schkct(c_ds_output_0, 8);
+            schkct(c_ds_output_1, 8);
+
+            c_ds_output_0 <: (synchronised_audio * unsafe)audio[buffer].data[0];
+            c_ds_output_1 <: (synchronised_audio * unsafe)audio[buffer].data[2];
+
+            buffer = 1 - buffer;
+
+            //The data has already been bit reversed in the downsampler
+
+            // audio[buffer] is good to go
+            //xscope_int(0, audio[buffer].data[0][0].ch_a);
+            //xscope_int(1, audio[buffer].data[0][0].ch_b);
+            c_pcm_out :> unsigned req;
+            c_pcm_out <: audio[buffer].data[0][0].ch_a;
+            c_pcm_out <: audio[buffer].data[0][0].ch_b;
+            printintln(audio[buffer].data[0][0].ch_b);
+        }
+    }
+}
+
+
+void pcm_pdm_mic(streaming chanend c_pcm_out)
+{
+    streaming chan c_multi_channel_pdm, c_sync, c_4x_pdm_mic_0, c_4x_pdm_mic_1;
+    streaming chan c_ds_output_0, c_ds_output_1;
+    streaming chan c_buffer_mic0, c_buffer_mic1;
+    unsigned long long shared_memory[2] = {0};
+
+    configure_clock_src(mclk, p_mclk);
+    configure_clock_src_divide(pdmclk, p_mclk, 2);
+    configure_port_clock_output(p_pdm_clk, pdmclk);
+    configure_in_port(p_pdm_mics, pdmclk);
+    start_clock(mclk);
+    start_clock(pdmclk);
+
+    unsafe 
+    {
+        unsigned long long * unsafe p_shared_memory = shared_memory;
+        par
+        {
+
+            //Input stage
+            pdm_first_stage(p_pdm_mics, p_shared_memory,
+                            PDM_BUFFER_LENGTH_LOG2, c_sync,
+                            c_4x_pdm_mic_0, c_4x_pdm_mic_1);
+
+            pdm_to_pcm_4x(c_4x_pdm_mic_0, c_ds_output_0);
+                    pdm_to_pcm_4x(c_4x_pdm_mic_1, c_ds_output_1);
+
+            example(c_ds_output_0, c_ds_output_1, c_pcm_out);
+
+        }
+    }
+}
+
+#endif