Prevent freezing USB during high frequency PulseIn.

We now track the last time the background task ran and bail on the
PulseIn if it starves the background work. In practice, this
happens after the numbers from pulsein are no longer accurate.

This also adjusts interrupt priorities so most are the lowest level
except for the tick and USB interrupts.

Fixes #516 and #876

2 files changed, 24 insertions, 0 deletions

diff --git a/shared-bindings/pulseio/PulseIn.c b/shared-bindings/pulseio/PulseIn.c
index 736441c74..862dbd99d 100644
--- a/shared-bindings/pulseio/PulseIn.c
+++ b/shared-bindings/pulseio/PulseIn.c
@@ -219,6 +219,26 @@ const mp_obj_property_t pulseio_pulsein_maxlen_obj = {
               (mp_obj_t)&mp_const_none_obj},
 };
 
+//|   .. attribute:: paused
+//|
+//|     True when pulse capture is paused as a result of :py:func:`pause` or an error during capture
+//|     such as a signal that is too fast.
+//|
+STATIC mp_obj_t pulseio_pulsein_obj_get_paused(mp_obj_t self_in) {
+    pulseio_pulsein_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    raise_error_if_deinited(common_hal_pulseio_pulsein_deinited(self));
+
+    return mp_obj_new_bool(common_hal_pulseio_pulsein_get_paused(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(pulseio_pulsein_get_paused_obj, pulseio_pulsein_obj_get_paused);
+
+const mp_obj_property_t pulseio_pulsein_paused_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&pulseio_pulsein_get_paused_obj,
+              (mp_obj_t)&mp_const_none_obj,
+              (mp_obj_t)&mp_const_none_obj},
+};
+
 //|   .. method:: __len__()
 //|
 //|     Returns the current pulse length
@@ -285,7 +305,10 @@ STATIC const mp_rom_map_elem_t pulseio_pulsein_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_resume), MP_ROM_PTR(&pulseio_pulsein_resume_obj) },
     { MP_ROM_QSTR(MP_QSTR_clear), MP_ROM_PTR(&pulseio_pulsein_clear_obj) },
     { MP_ROM_QSTR(MP_QSTR_popleft), MP_ROM_PTR(&pulseio_pulsein_popleft_obj) },
+
+    // Properties
     { MP_ROM_QSTR(MP_QSTR_maxlen), MP_ROM_PTR(&pulseio_pulsein_maxlen_obj) },
+    { MP_ROM_QSTR(MP_QSTR_paused), MP_ROM_PTR(&pulseio_pulsein_paused_obj) },
 };
 STATIC MP_DEFINE_CONST_DICT(pulseio_pulsein_locals_dict, pulseio_pulsein_locals_dict_table);
 
diff --git a/shared-bindings/pulseio/PulseIn.h b/shared-bindings/pulseio/PulseIn.h
index 88b6f356e..e28a3c2df 100644
--- a/shared-bindings/pulseio/PulseIn.h
+++ b/shared-bindings/pulseio/PulseIn.h
@@ -41,6 +41,7 @@ extern void common_hal_pulseio_pulsein_resume(pulseio_pulsein_obj_t* self, uint1
 extern void common_hal_pulseio_pulsein_clear(pulseio_pulsein_obj_t* self);
 extern uint16_t common_hal_pulseio_pulsein_popleft(pulseio_pulsein_obj_t* self);
 extern uint16_t common_hal_pulseio_pulsein_get_maxlen(pulseio_pulsein_obj_t* self);
+extern bool common_hal_pulseio_pulsein_get_paused(pulseio_pulsein_obj_t* self);
 extern uint16_t common_hal_pulseio_pulsein_get_len(pulseio_pulsein_obj_t* self);
 extern uint16_t common_hal_pulseio_pulsein_get_item(pulseio_pulsein_obj_t* self, int16_t index);