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module_usb_midi/src/midioutparse.xc

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+/**
+ * @file midioutparse.xc
+ * @brief Parses USB-MIDI events into set of MIDI bytes
+ * @author Russell Gallop, XMOS Semiconductor 
+ * @version 0.1
+ */
+
+#include "midioutparse.h"
+
+/** 
+ * @brief Breaks a USB-MIDI event into it's constituant fields
+ *
+ * @param[in]   ev    USB-MIDI event
+ */
+{unsigned, unsigned, unsigned, unsigned, unsigned} breakEvent(unsigned ev) {
+    unsigned cable_number = (ev >> 28) & 0xf;
+    unsigned codeIndexNumber = (ev >> 24) & 0xf;
+    unsigned midi0 = (ev >> 16) & 0xff;
+    unsigned midi1 = (ev >> 8) & 0xff;
+    unsigned midi2 = (ev >> 0) & 0xff;
+    return {cable_number, codeIndexNumber, midi0, midi1, midi2};
+}
+
+/** 
+ * @brief Parse a USB-MIDI event into the MIDI bytes and a length field
+ *
+ * @param[in]   ev    USB-MIDI event
+ */
+{unsigned, unsigned, unsigned, unsigned} midi_out_parse(unsigned event) {
+    unsigned cable_number; // ignore this for now!
+    unsigned codeIndexNumber;
+    unsigned midi[3];
+    unsigned size = 0;
+
+    {cable_number, codeIndexNumber, midi[0], midi[1], midi[2]} = breakEvent(event);
+    // Not doing anything with cable number
+    switch (codeIndexNumber) {
+    case 0x3: // Three-byte system Common messages like SPP, etc.
+    case 0x4: // SysEx starts or continues
+    case 0x7: // SysEx ends with the following three bytes
+    case 0x8: // Note-off
+    case 0x9: // Note-on
+    case 0xA: // Poly-KeyPress
+    case 0xB: // Control Change
+    case 0xE: // PitchBend Change
+    {
+        size = 3;
+        break;
+    }
+    case 0x2: // Two-byte system Common messages like MTC, SongSelect, etc.
+    case 0x6: // SysEx ends with the following two bytes
+    case 0xC: // Program Change
+    case 0xD: // Channel Pressure
+    {
+        size = 2;
+        break;
+    }
+    case 0x5: // Single-byte System Common Message or SysEx ends with following single byte.
+    case 0xF: // Single byte
+    {
+        size = 1;
+        break;
+    }
+    default:
+        break;
+    }
+    return {midi[0], midi[1], midi[2], size};
+}