synthio: add (untested) phase offset

Author: jepler

shared-bindings/synthio/LFO.c

@@ -63,6 +63,7 @@
 //|         rate: BlockInput = 1.0,
 //|         scale: BlockInput = 1.0,
 //|         offset: BlockInput = 0,
+//|         phase_offset: BlockInput = 0,
 //|         once=False
 //|     ):
 //|         pass
@@ -71,6 +72,7 @@ static const mp_arg_t lfo_properties[] = {
     { MP_QSTR_rate, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(1) } },
     { MP_QSTR_scale, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(1) } },
     { MP_QSTR_offset, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(0) } },
+    { MP_QSTR_phase_offset, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(0) } },
     { MP_QSTR_once, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(0) } },
 };
 
@@ -141,6 +143,24 @@ MP_PROPERTY_GETSET(synthio_lfo_offset_obj,
     (mp_obj_t)&synthio_lfo_get_offset_obj,
     (mp_obj_t)&synthio_lfo_set_offset_obj);
 
+//|     phase_offset: BlockInput
+//|     """An additive value applied to the LFO's phase"""
+STATIC mp_obj_t synthio_lfo_get_phase_offset(mp_obj_t self_in) {
+    synthio_lfo_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return common_hal_synthio_lfo_get_phase_offset_obj(self);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(synthio_lfo_get_phase_offset_obj, synthio_lfo_get_phase_offset);
+
+STATIC mp_obj_t synthio_lfo_set_phase_offset(mp_obj_t self_in, mp_obj_t arg) {
+    synthio_lfo_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    common_hal_synthio_lfo_set_phase_offset_obj(self, arg);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(synthio_lfo_set_phase_offset_obj, synthio_lfo_set_phase_offset);
+MP_PROPERTY_GETSET(synthio_lfo_phase_offset_obj,
+    (mp_obj_t)&synthio_lfo_get_phase_offset_obj,
+    (mp_obj_t)&synthio_lfo_set_phase_offset_obj);
+
 //|     scale: BlockInput
 //|     """An additive value applied to the LFO's output"""
 STATIC mp_obj_t synthio_lfo_get_scale(mp_obj_t self_in) {
@@ -161,7 +181,9 @@ MP_PROPERTY_GETSET(synthio_lfo_scale_obj,
 
 //|
 //|     once: bool
-//|     """True if the waveform should stop when it reaches its last output value, false if it should re-start at the beginning of its waveform"""
+//|     """True if the waveform should stop when it reaches its last output value, false if it should re-start at the beginning of its waveform
+//|
+//|     This applies to the ``phase`` *before* the addition of any ``phase_offset`` """
 STATIC mp_obj_t synthio_lfo_get_once(mp_obj_t self_in) {
     synthio_lfo_obj_t *self = MP_OBJ_TO_PTR(self_in);
     return mp_obj_new_bool(common_hal_synthio_lfo_get_once(self));
@@ -226,6 +248,7 @@ STATIC const mp_rom_map_elem_t synthio_lfo_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_rate), MP_ROM_PTR(&synthio_lfo_rate_obj) },
     { MP_ROM_QSTR(MP_QSTR_scale), MP_ROM_PTR(&synthio_lfo_scale_obj) },
     { MP_ROM_QSTR(MP_QSTR_offset), MP_ROM_PTR(&synthio_lfo_offset_obj) },
+    { MP_ROM_QSTR(MP_QSTR_phase_offset), MP_ROM_PTR(&synthio_lfo_phase_offset_obj) },
     { MP_ROM_QSTR(MP_QSTR_once), MP_ROM_PTR(&synthio_lfo_once_obj) },
     { MP_ROM_QSTR(MP_QSTR_value), MP_ROM_PTR(&synthio_lfo_value_obj) },
     { MP_ROM_QSTR(MP_QSTR_phase), MP_ROM_PTR(&synthio_lfo_phase_obj) },

shared-bindings/synthio/LFO.h

@@ -40,6 +40,9 @@ void common_hal_synthio_lfo_set_rate_obj(synthio_lfo_obj_t *self, mp_obj_t arg);
 mp_obj_t common_hal_synthio_lfo_get_scale_obj(synthio_lfo_obj_t *self);
 void common_hal_synthio_lfo_set_scale_obj(synthio_lfo_obj_t *self, mp_obj_t arg);
 
+mp_obj_t common_hal_synthio_lfo_get_phase_offset_obj(synthio_lfo_obj_t *self);
+void common_hal_synthio_lfo_set_phase_offset_obj(synthio_lfo_obj_t *self, mp_obj_t arg);
+
 mp_obj_t common_hal_synthio_lfo_get_offset_obj(synthio_lfo_obj_t *self);
 void common_hal_synthio_lfo_set_offset_obj(synthio_lfo_obj_t *self, mp_obj_t arg);
 

shared-module/synthio/LFO.c

@@ -35,32 +35,32 @@ mp_float_t common_hal_synthio_lfo_tick(mp_obj_t self_in) {
     synthio_lfo_obj_t *lfo = MP_OBJ_TO_PTR(self_in);
 
     mp_float_t rate = synthio_block_slot_get(&lfo->rate) * synthio_global_rate_scale;
+    mp_float_t phase_offset = synthio_block_slot_get(&lfo->phase_offset);
 
-    mp_float_t accum = lfo->accum + rate;
-    mp_float_t frac = accum - MICROPY_FLOAT_C_FUN(floor)(accum);
-    size_t idx = (int)(frac * len);
+    mp_float_t accum = lfo->accum + rate + phase_offset;
 
     if (lfo->once) {
         if (rate > 0) {
             if (accum >= ONE) {
-                frac = ONE;
-                idx = len - 1;
+                accum = ONE;
             }
         } else if (rate < 0 && accum < ZERO) {
-            frac = ZERO;
-            idx = 0;
+            accum = ZERO;
         }
+    } else {
+        accum = accum - MICROPY_FLOAT_C_FUN(floor)(accum);
     }
 
     int len = lfo->waveform_bufinfo.len;
-    lfo->accum = frac;
+    size_t idx = (int)(accum * len); // rounds down towards zero
+    assert(idx < lfo->waveform_bufinfo.len);
 
-    int16_t *waveform = lfo->waveform_bufinfo.buf;
-    assert(idx < lfo->waveform_bufinfo.len / 2);
     mp_float_t scale = synthio_block_slot_get(&lfo->scale);
     mp_float_t offset = synthio_block_slot_get(&lfo->offset);
+    int16_t *waveform = lfo->waveform_bufinfo.buf;
     mp_float_t value = MICROPY_FLOAT_C_FUN(ldexp)(waveform[idx], -15) * scale + offset;
 
+    lfo->accum = accum - phase_offset;
     return value;
 }
 
@@ -83,6 +83,13 @@ void common_hal_synthio_lfo_set_scale_obj(synthio_lfo_obj_t *self, mp_obj_t arg)
     synthio_block_assign_slot(arg, &self->scale, MP_QSTR_scale);
 }
 
+mp_obj_t common_hal_synthio_lfo_get_phase_offset_obj(synthio_lfo_obj_t *self) {
+    return self->phase_offset.obj;
+}
+void common_hal_synthio_lfo_set_phase_offset_obj(synthio_lfo_obj_t *self, mp_obj_t arg) {
+    synthio_block_assign_slot(arg, &self->phase_offset, MP_QSTR_phase_offset);
+}
+
 mp_obj_t common_hal_synthio_lfo_get_offset_obj(synthio_lfo_obj_t *self) {
     return self->offset.obj;
 }

shared-module/synthio/LFO.h

@@ -32,7 +32,7 @@ typedef struct synthio_lfo_obj {
     synthio_block_base_t base;
     bool once;
 
-    synthio_block_slot_t rate, scale, offset;
+    synthio_block_slot_t rate, scale, offset, phase_offset;
     mp_float_t accum;
 
     mp_obj_t waveform_obj;