codal_port/microbit_pinmode: Allow grabbing a pin in music mode if idle.

If a pin is in music mode but there is no audio/music currently active,
then allow it to be grabbed for use as any other mode.  Otherwise raise an
exception that it is in use in music mode.

Addresses issue #50.

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

Author: dpgeorge

src/codal_port/microbit_pinmode.c

@@ -25,7 +25,9 @@
  */
 
 #include "py/runtime.h"
+#include "modaudio.h"
 #include "modmicrobit.h"
+#include "modmusic.h"
 
 uint8_t microbit_pinmode_indices[32] = { 0 };
 
@@ -84,14 +86,22 @@ static void analog_release(const microbit_pin_obj_t *pin) {
     // TODO: pwm_release()
 }
 
+static void music_release(const microbit_pin_obj_t *pin) {
+    if (microbit_audio_is_playing() || microbit_music_is_playing()) {
+        pinmode_error(pin);
+    } else {
+        microbit_pin_audio_free();
+    }
+}
+
 const microbit_pinmode_t microbit_pinmodes[] = {
     [MODE_UNUSED]        = { MP_QSTR_unused, noop },
     [MODE_WRITE_ANALOG]  = { MP_QSTR_write_analog, analog_release },
     [MODE_READ_DIGITAL]  = { MP_QSTR_read_digital, noop },
     [MODE_WRITE_DIGITAL] = { MP_QSTR_write_digital, noop },
     [MODE_DISPLAY]       = { MP_QSTR_display, pinmode_error },
     [MODE_BUTTON]        = { MP_QSTR_button, pinmode_error },
-    [MODE_MUSIC]         = { MP_QSTR_music, pinmode_error },
+    [MODE_MUSIC]         = { MP_QSTR_music, music_release },
     [MODE_AUDIO_PLAY]    = { MP_QSTR_audio, noop },
     [MODE_TOUCH]         = { MP_QSTR_touch, noop },
     [MODE_I2C]           = { MP_QSTR_i2c, pinmode_error },

src/codal_port/modaudio.c

@@ -205,11 +205,11 @@ STATIC mp_obj_t play(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_ar
 MP_DEFINE_CONST_FUN_OBJ_KW(microbit_audio_play_obj, 0, play);
 
 bool microbit_audio_is_playing(void) {
-    return audio_running;
+    return audio_running || microbit_hal_audio_is_expression_active();
 }
 
 mp_obj_t is_playing(void) {
-    return mp_obj_new_bool(audio_running);
+    return mp_obj_new_bool(microbit_audio_is_playing());
 }
 MP_DEFINE_CONST_FUN_OBJ_0(microbit_audio_is_playing_obj, is_playing);
 

src/codal_port/modmusic.c

@@ -76,6 +76,10 @@ STATIC int music_output_period_us(uint32_t period) {
     return microbit_hal_pin_set_analog_period_us(MICROBIT_HAL_PIN_MIXER, period);
 }
 
+bool microbit_music_is_playing(void) {
+    return music_data != NULL && music_data->async_state != ASYNC_MUSIC_STATE_IDLE;
+}
+
 // This runs on a hardware interrupt.
 void microbit_music_tick(void) {
     if (music_data == NULL) {

src/codal_port/modmusic.h

@@ -51,6 +51,7 @@ extern const struct _mp_obj_tuple_t microbit_music_tune_power_up_obj;
 extern const struct _mp_obj_tuple_t microbit_music_tune_power_down_obj;
 
 void microbit_music_volume_changed(void);
+bool microbit_music_is_playing(void);
 void microbit_music_tick(void);
 
 #endif // MICROPY_INCLUDED_MICROBIT_MUSIC_H