codal_port/modaudio: Support playing a tuple/list of SoundEffect's.

For simplicity of implementation, this just concatenates the tuple/list of
SoundEffect's into a big string to be passed directly to CODAL.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/microbit_soundeffect.c

@@ -28,8 +28,6 @@
 #include "modmicrobit.h"
 #include "modaudio.h"
 
-#define SOUND_EXPR_TOTAL_LENGTH                 (72)
-
 #define SOUND_EXPR_WAVE_OFFSET                  (0)
 #define SOUND_EXPR_WAVE_LENGTH                  (1)
 #define SOUND_EXPR_VOLUME_START_OFFSET          (1)

src/codal_port/modaudio.c

@@ -143,6 +143,24 @@ void microbit_audio_play_source(mp_obj_t src, mp_obj_t pin_select, bool wait, ui
         sound_expr_data = sound->name;
     } else if (mp_obj_is_type(src, &microbit_soundeffect_type)) {
         sound_expr_data = microbit_soundeffect_get_sound_expr_data(src);
+    } else if (mp_obj_is_type(src, &mp_type_tuple) || mp_obj_is_type(src, &mp_type_list)) {
+        // A tuple/list passed in.  Need to check if it contains SoundEffect instances.
+        size_t len;
+        mp_obj_t *items;
+        mp_obj_get_array(src, &len, &items);
+        if (len > 0 && mp_obj_is_type(items[0], &microbit_soundeffect_type)) {
+            // A tuple/list of SoundEffect instances.  Convert it to a long string of
+            // sound expression data, each effect separated by a ",".
+            char *data = m_new(char, len * (SOUND_EXPR_TOTAL_LENGTH + 1));
+            sound_expr_data = data;
+            for (size_t i = 0; i < len; ++i) {
+                memcpy(data, microbit_soundeffect_get_sound_expr_data(items[i]), SOUND_EXPR_TOTAL_LENGTH);
+                data += SOUND_EXPR_TOTAL_LENGTH;
+                *data++ = ',';
+            }
+            // Replace last "," with a string null terminator.
+            data[-1] = '\0';
+        }
     }
 
     if (sound_expr_data != NULL) {

src/codal_port/modaudio.h

@@ -32,6 +32,8 @@
 #define LOG_AUDIO_CHUNK_SIZE (5)
 #define AUDIO_CHUNK_SIZE (1 << LOG_AUDIO_CHUNK_SIZE)
 
+#define SOUND_EXPR_TOTAL_LENGTH (72)
+
 typedef struct _microbit_audio_frame_obj_t {
     mp_obj_base_t base;
     uint8_t data[AUDIO_CHUNK_SIZE];