codal_port/modaudio: Add audio.set_rate() function.

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

Author: dpgeorge

src/codal_port/modaudio.c

@@ -246,6 +246,16 @@ void microbit_audio_play_source(mp_obj_t src, mp_obj_t pin_select, bool wait, ui
     }
 }
 
+STATIC mp_obj_t microbit_audio_set_rate(mp_obj_t sample_rate_in) {
+    mp_float_t sample_rate = mp_obj_get_float(sample_rate_in);
+    if (sample_rate <= 0) {
+        mp_raise_ValueError(MP_ERROR_TEXT("invalid sample rate"));
+    }
+    microbit_hal_audio_raw_set_rate(sample_rate);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_1(microbit_audio_set_rate_obj, microbit_audio_set_rate);
+
 STATIC mp_obj_t stop(void) {
     microbit_audio_stop();
     return mp_const_none;
@@ -285,6 +295,7 @@ MP_DEFINE_CONST_FUN_OBJ_0(microbit_audio_is_playing_obj, is_playing);
 
 STATIC const mp_rom_map_elem_t audio_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_audio) },
+    { MP_ROM_QSTR(MP_QSTR_set_rate), MP_ROM_PTR(&microbit_audio_set_rate_obj) },
     { MP_ROM_QSTR(MP_QSTR_stop), MP_ROM_PTR(&microbit_audio_stop_obj) },
     { MP_ROM_QSTR(MP_QSTR_play), MP_ROM_PTR(&microbit_audio_play_obj) },
     { MP_ROM_QSTR(MP_QSTR_is_playing), MP_ROM_PTR(&microbit_audio_is_playing_obj) },