merge from upstream and make translate

50 files changed, 513 insertions, 123 deletions

diff --git a/.travis.yml b/.travis.yml
index 9bfcd61f0..9a058aa64 100755
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,20 +12,32 @@ git:
 # pip packages, and so forth.  By gathering activities together in optimal
 # ways, the "run time" and "total time" of the travis jobs can be minimized.
 #
-# Since at the time of writing Travis generally starts 5 or 6 jobs, the
-# builds have been organized into 5 groups of *approximately* equal durations.
-# Additionally, the jobs that need extra SDKs are also organized together.
+# Builds are organized so some will complete quickly, and others are of
+# approximately equal size. Try not to freeze out other Travis users.
+#
+# Board names are in alphabetical order for easy finding, but grouped by
+# Adafruit/modified-Adafruit and Other. Ideally they'd be separated into
+# separate jobs, but there are too many.
 #
 # When adding new boards, take a look on the travis CI page
 # https://travis-ci.org/adafruit/circuitpython to which build that installs
 # that SDK is shortest and add it there.  In the case of major re-organizations,
 # just try to make the builds "about equal in run time"
 env:
-  - TRAVIS_TESTS="unix docs translations website" TRAVIS_BOARDS="trinket_m0_haxpress circuitplayground_express mini_sam_m4 grandcentral_m4_express capablerobot_usbhub pygamer pca10056 pca10059 feather_nrf52840_express metro_nrf52840_express circuitplayground_bluefruit makerdiary_nrf52840_mdk makerdiary_nrf52840_mdk_usb_dongle particle_boron particle_argon particle_xenon sparkfun_nrf52840_mini electronut_labs_papyr electronut_labs_blip" TRAVIS_SDK=arm:nrf
-  - TRAVIS_BOARDS="metro_m0_express metro_m4_express metro_m4_airlift_lite pirkey_m0 trellis_m4_express trinket_m0 sparkfun_lumidrive sparkfun_redboard_turbo bast_pro_mini_m0 datum_distance pyruler" TRAVIS_SDK=arm
-  - TRAVIS_BOARDS="cp32-m4 feather_radiofruit_zigbee gemma_m0 hallowing_m0_express itsybitsy_m0_express itsybitsy_m4_express meowmeow sam32 uchip escornabot_makech pygamer_advance datum_imu snekboard" TRAVIS_SDK=arm
-  - TRAVIS_BOARDS="feather_m0_supersized feather_m0_express_crickit feather_m0_rfm69 feather_m0_rfm9x feather_m4_express arduino_zero arduino_mkr1300 arduino_mkrzero pewpew10 kicksat-sprite ugame10 robohatmm1_m0 robohatmm1_m4 datum_light" TRAVIS_SDK=arm
-  - TRAVIS_BOARDS="datalore_ip_m4 circuitplayground_express_crickit feather_m0_adalogger feather_m0_basic feather_m0_express catwan_usbstick pyportal sparkfun_samd21_mini sparkfun_samd21_dev pybadge pybadge_airlift datum_weather pyportal_titano" TRAVIS_SDK=arm
+  # Non-board tasks
+  - TRAVIS_TESTS="unix docs translations website" TRAVIS_BOARDS=""
+  # Adafruit and Nordic nRF boards
+  - TRAVIS_BOARDS="circuitplayground_bluefruit feather_nrf52840_express metro_nrf52840_express pca10056 pca10059" TRAVIS_SDK=arm
+  # Other nRF boards
+  - TRAVIS_BOARDS="electronut_labs_blip electronut_labs_papyr makerdiary_nrf52840_mdk makerdiary_nrf52840_mdk_usb_dongle particle_argon particle_boron particle_xenon sparkfun_nrf52840_mini" TRAVIS_SDK=arm
+  # Adafruit and modified Adafruit SAMD21 (M0) + Other SAMD21 (M0)
+  - TRAVIS_BOARDS="circuitplayground_express circuitplayground_express_crickit feather_m0_adalogger feather_m0_basic feather_m0_express feather_m0_express_crickit feather_m0_rfm69 feather_m0_rfm9x feather_m0_supersized feather_radiofruit_zigbee gemma_m0 hallowing_m0_express " TRAVIS_SDK=arm
+  - TRAVIS_BOARDS="itsybitsy_m0_express metro_m0_express pirkey_m0 pyruler trinket_m0 trinket_m0_haxpress arduino_mkr1300 arduino_mkrzero arduino_zero bast_pro_mini_m0 catwan_usbstick datum_distance datum_imu datum_weather" TRAVIS_SDK=arm
+  - TRAVIS_BOARDS="escornabot_makech meowmeow pewpew10 robohatmm1_m0 snekboard sparkfun_lumidrive sparkfun_redboard_turbo sparkfun_samd21_dev sparkfun_samd21_mini uchip ugame10" TRAVIS_SDK=arm
+  # Adafruit SAMD51 (M4) + Other SAMD51
+  - TRAVIS_BOARDS="feather_m4_express grandcentral_m4_express itsybitsy_m4_express metro_m4_airlift_lite metro_m4_express pybadge pybadge_airlift pygamer pygamer_advance" TRAVIS_SDK=arm
+  - TRAVIS_BOARDS="pyportal pyportal_titano trellis_m4_express capablerobot_usbhub cp32-m4 datalore_ip_m4 datum_light kicksat-sprite mini_sam_m4 robohatmm1_m4 sam32" TRAVIS_SDK=arm
+
 
 addons:
   artifacts:
diff --git a/locale/ID.po b/locale/ID.po
index 9041b4cb0..d8758374e 100644
--- a/locale/ID.po
+++ b/locale/ID.po
@@ -1138,7 +1138,7 @@ msgid "Slices not supported"
 msgstr ""
 
 #: ports/nrf/common-hal/bleio/Adapter.c
-#, c-format
+#, fuzzy, c-format
 msgid "Soft device assert, id: 0x%08lX, pc: 0x%08lX"
 msgstr "Dukungan soft device, id: 0x%08lX, pc: 0x%08l"
 
@@ -2284,6 +2284,14 @@ msgstr "panjang data string memiliki keganjilan (odd-length)"
 msgid "offset out of bounds"
 msgstr "modul tidak ditemukan"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/circuitpython.pot b/locale/circuitpython.pot
index fa189db79..2ccb77d5f 100644
--- a/locale/circuitpython.pot
+++ b/locale/circuitpython.pot
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2019-08-20 13:01-0400\n"
+"POT-Creation-Date: 2019-08-20 13:06-0400\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -2248,6 +2248,14 @@ msgstr ""
 msgid "offset out of bounds"
 msgstr ""
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/de_DE.po b/locale/de_DE.po
index aadff2ac9..a90e5c46e 100644
--- a/locale/de_DE.po
+++ b/locale/de_DE.po
@@ -2295,6 +2295,14 @@ msgstr "String mit ungerader Länge"
 msgid "offset out of bounds"
 msgstr "offset außerhalb der Grenzen"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/en_US.po b/locale/en_US.po
index 1b1c44d86..c7599388f 100644
--- a/locale/en_US.po
+++ b/locale/en_US.po
@@ -2248,6 +2248,14 @@ msgstr ""
 msgid "offset out of bounds"
 msgstr ""
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/en_x_pirate.po b/locale/en_x_pirate.po
index c6bb116e5..34bb307f3 100644
--- a/locale/en_x_pirate.po
+++ b/locale/en_x_pirate.po
@@ -2252,6 +2252,14 @@ msgstr ""
 msgid "offset out of bounds"
 msgstr ""
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/es.po b/locale/es.po
index 8be76c9df..5a4f270ef 100644
--- a/locale/es.po
+++ b/locale/es.po
@@ -635,7 +635,7 @@ msgstr "No se puede leer el valor del atributo. err 0x%02x"
 
 #: ports/nrf/common-hal/bleio/Characteristic.c
 #: ports/nrf/common-hal/bleio/Descriptor.c
-#, c-format
+#, fuzzy, c-format
 msgid "Failed to read attribute value, err 0x%04x"
 msgstr "Error al leer valor del atributo, err 0x%04"
 
@@ -2311,6 +2311,14 @@ msgstr "string de longitud impar"
 msgid "offset out of bounds"
 msgstr "address fuera de límites"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/fil.po b/locale/fil.po
index 93afc5998..65b73cc6d 100644
--- a/locale/fil.po
+++ b/locale/fil.po
@@ -2320,6 +2320,14 @@ msgstr "odd-length string"
 msgid "offset out of bounds"
 msgstr "wala sa sakop ang address"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/fr.po b/locale/fr.po
index 4a1b9c312..cf35d2044 100644
--- a/locale/fr.po
+++ b/locale/fr.po
@@ -2356,6 +2356,14 @@ msgstr "chaîne de longueur impaire"
 msgid "offset out of bounds"
 msgstr "adresse hors limites"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/it_IT.po b/locale/it_IT.po
index f8080fe85..96227d0ce 100644
--- a/locale/it_IT.po
+++ b/locale/it_IT.po
@@ -112,7 +112,7 @@ msgid "'%s' expects {r0, r1, ...}"
 msgstr "'%s' aspetta un registro"
 
 #: py/emitinlinextensa.c
-#, c-format
+#, fuzzy, c-format
 msgid "'%s' integer %d is not within range %d..%d"
 msgstr "intero '%s' non è nell'intervallo %d..%d"
 
@@ -1566,7 +1566,7 @@ msgid "can't assign to expression"
 msgstr "impossibile assegnare all'espressione"
 
 #: py/obj.c
-#, c-format
+#, fuzzy, c-format
 msgid "can't convert %s to complex"
 msgstr "non è possibile convertire a complex"
 
@@ -2316,6 +2316,14 @@ msgstr "stringa di lunghezza dispari"
 msgid "offset out of bounds"
 msgstr "indirizzo fuori limite"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
@@ -2637,7 +2645,7 @@ msgid "unindent does not match any outer indentation level"
 msgstr ""
 
 #: py/objstr.c
-#, c-format
+#, fuzzy, c-format
 msgid "unknown conversion specifier %c"
 msgstr "specificatore di conversione %s sconosciuto"
 
diff --git a/locale/pl.po b/locale/pl.po
index 33a825239..7a242835d 100644
--- a/locale/pl.po
+++ b/locale/pl.po
@@ -559,12 +559,12 @@ msgid "Failed sending command."
 msgstr ""
 
 #: ports/nrf/sd_mutex.c
-#, c-format
+#, fuzzy, c-format
 msgid "Failed to acquire mutex, err 0x%04x"
 msgstr "Nie udało się uzyskać blokady, błąd 0x$04x"
 
 #: ports/nrf/common-hal/bleio/Service.c
-#, c-format
+#, fuzzy, c-format
 msgid "Failed to add characteristic, err 0x%04x"
 msgstr "Nie udało się dodać charakterystyki, błąd 0x$04x"
 
@@ -2273,6 +2273,14 @@ msgstr "łańcuch o nieparzystej długości"
 msgid "offset out of bounds"
 msgstr "offset poza zakresem"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/pt_BR.po b/locale/pt_BR.po
index aed356137..2a5b62ec1 100644
--- a/locale/pt_BR.po
+++ b/locale/pt_BR.po
@@ -2274,6 +2274,14 @@ msgstr ""
 msgid "offset out of bounds"
 msgstr ""
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
diff --git a/locale/zh_Latn_pinyin.po b/locale/zh_Latn_pinyin.po
index d3bfa2fe7..67f329080 100644
--- a/locale/zh_Latn_pinyin.po
+++ b/locale/zh_Latn_pinyin.po
@@ -2287,6 +2287,14 @@ msgstr "jīshù zìfú chuàn"
 msgid "offset out of bounds"
 msgstr "piānlí biānjiè"
 
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only bit_depth=16 is supported"
+msgstr ""
+
+#: ports/nrf/common-hal/audiobusio/PDMIn.c
+msgid "only sample_rate=16000 is supported"
+msgstr ""
+
 #: py/objarray.c py/objstr.c py/objstrunicode.c py/objtuple.c
 #: shared-bindings/nvm/ByteArray.c
 msgid "only slices with step=1 (aka None) are supported"
@@ -2607,7 +2615,7 @@ msgid "unknown conversion specifier %c"
 msgstr "wèizhī de zhuǎnhuàn biāozhù %c"
 
 #: py/objstr.c
-#, c-format
+#, fuzzy, c-format
 msgid "unknown format code '%c' for object of type '%s'"
 msgstr "lèixíng '%s' duìxiàng wèizhī de géshì dàimǎ '%c'"
 
diff --git a/ports/atmel-samd/common-hal/audiobusio/PDMIn.c b/ports/atmel-samd/common-hal/audiobusio/PDMIn.c
index da5c220a8..76010a684 100644
--- a/ports/atmel-samd/common-hal/audiobusio/PDMIn.c
+++ b/ports/atmel-samd/common-hal/audiobusio/PDMIn.c
@@ -408,9 +408,7 @@ uint32_t common_hal_audiobusio_pdmin_record_to_buffer(audiobusio_pdmin_obj_t* se
         // If wait_counts exceeds the max count, buffer has probably stopped filling;
         // DMA may have missed an I2S trigger event.
         while (!event_interrupt_active(event_channel) && ++wait_counts < MAX_WAIT_COUNTS) {
-            #ifdef MICROPY_VM_HOOK_LOOP
-                MICROPY_VM_HOOK_LOOP
-            #endif
+            RUN_BACKGROUND_TASKS;
         }
 
         // The mic is running all the time, so we don't need to wait the usual 10msec or 100msec
diff --git a/ports/atmel-samd/common-hal/audioio/AudioOut.c b/ports/atmel-samd/common-hal/audioio/AudioOut.c
index a75abd324..90f1aa41f 100644
--- a/ports/atmel-samd/common-hal/audioio/AudioOut.c
+++ b/ports/atmel-samd/common-hal/audioio/AudioOut.c
@@ -69,9 +69,7 @@ static void ramp_value(uint16_t start, uint16_t end) {
         DAC->DATA.reg = value;
         DAC->DATABUF.reg = value;
         common_hal_mcu_delay_us(50);
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
     }
 }
 #endif
@@ -94,9 +92,7 @@ static void ramp_value(uint16_t start, uint16_t end) {
         DAC->DATABUF[1].reg = value;
 
         common_hal_mcu_delay_us(50);
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
     }
 }
 #endif
diff --git a/ports/atmel-samd/common-hal/busio/UART.c b/ports/atmel-samd/common-hal/busio/UART.c
index f04594842..2505e894a 100644
--- a/ports/atmel-samd/common-hal/busio/UART.c
+++ b/ports/atmel-samd/common-hal/busio/UART.c
@@ -291,13 +291,11 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
             // Reset the timeout on every character read.
             start_ticks = ticks_ms;
         }
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
+        RUN_BACKGROUND_TASKS;
         // Allow user to break out of a timeout with a KeyboardInterrupt.
         if (mp_hal_is_interrupted()) {
             break;
         }
-#endif
         // If we are zero timeout, make sure we don't loop again (in the event
         // we read in under 1ms)
         if (self->timeout_ms == 0) {
@@ -339,9 +337,7 @@ size_t common_hal_busio_uart_write(busio_uart_obj_t *self, const uint8_t *data,
             done = true;
             break;
         }
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
     }
 
     if (!done) {
diff --git a/ports/atmel-samd/common-hal/pulseio/PulseOut.c b/ports/atmel-samd/common-hal/pulseio/PulseOut.c
index 528a5c808..8b8bc6dc6 100644
--- a/ports/atmel-samd/common-hal/pulseio/PulseOut.c
+++ b/ports/atmel-samd/common-hal/pulseio/PulseOut.c
@@ -198,9 +198,7 @@ void common_hal_pulseio_pulseout_send(pulseio_pulseout_obj_t* self, uint16_t* pu
     while(pulse_index < length) {
         // Do other things while we wait. The interrupts will handle sending the
         // signal.
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
     }
 
     tc->COUNT16.CTRLBSET.reg = TC_CTRLBSET_CMD_STOP;
diff --git a/ports/atmel-samd/common-hal/touchio/TouchIn.c b/ports/atmel-samd/common-hal/touchio/TouchIn.c
index 0658c1d05..908d8d722 100644
--- a/ports/atmel-samd/common-hal/touchio/TouchIn.c
+++ b/ports/atmel-samd/common-hal/touchio/TouchIn.c
@@ -52,9 +52,7 @@ static uint16_t get_raw_reading(touchio_touchin_obj_t *self) {
 
     while (!adafruit_ptc_is_conversion_finished(PTC)) {
         // wait
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
     }
 
     return adafruit_ptc_get_conversion_result(PTC);
diff --git a/ports/atmel-samd/mphalport.c b/ports/atmel-samd/mphalport.c
index 5c34a576a..957bf6073 100644
--- a/ports/atmel-samd/mphalport.c
+++ b/ports/atmel-samd/mphalport.c
@@ -53,9 +53,7 @@ void mp_hal_delay_ms(mp_uint_t delay) {
     uint64_t start_tick = ticks_ms;
     uint64_t duration = 0;
     while (duration < delay) {
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
         // Check to see if we've been CTRL-Ced by autoreload or the user.
         if(MP_STATE_VM(mp_pending_exception) == MP_OBJ_FROM_PTR(&MP_STATE_VM(mp_kbd_exception)) ||
            MP_STATE_VM(mp_pending_exception) == MP_OBJ_FROM_PTR(&MP_STATE_VM(mp_reload_exception))) {
diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index 9da2c498d..9a461f9d8 100755
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -95,8 +95,7 @@ ifeq ($(DEBUG), 1)
   CFLAGS += -fno-inline -fno-ipa-sra
 else
   CFLAGS += -Os -DNDEBUG
-  # TODO: Test with -flto
-  ### CFLAGS += -flto
+  CFLAGS += -flto -flto-partition=none
 endif
 
 
@@ -185,8 +184,7 @@ SRC_C += \
 # USB source files for nrf52840
 ifeq ($(MCU_SUB_VARIANT),nrf52840)
 SRC_C += \
-	lib/tinyusb/src/portable/nordic/nrf5x/dcd_nrf5x.c \
-	lib/tinyusb/src/portable/nordic/nrf5x/hal_nrf5x.c
+	lib/tinyusb/src/portable/nordic/nrf5x/dcd_nrf5x.c
 endif
 
 SRC_COMMON_HAL_EXPANDED = $(addprefix shared-bindings/, $(SRC_COMMON_HAL)) \
diff --git a/ports/nrf/bluetooth/ble_uart.c b/ports/nrf/bluetooth/ble_uart.c
index 91d10cff1..d83cf3980 100644
--- a/ports/nrf/bluetooth/ble_uart.c
+++ b/ports/nrf/bluetooth/ble_uart.c
@@ -138,9 +138,7 @@ void ble_uart_init(void) {
     m_cccd_enabled = false;
 
     while (!m_cccd_enabled) {
-#ifdef MICROPY_VM_HOOK_LOOP
-    MICROPY_VM_HOOK_LOOP
-#endif
+        RUN_BACKGROUND_TASKS;
     }
 }
 
@@ -150,9 +148,7 @@ bool ble_uart_connected(void) {
 
 char ble_uart_rx_chr(void) {
     while (isBufferEmpty(&m_rx_ring_buffer)) {
-#ifdef MICROPY_VM_HOOK_LOOP
-    MICROPY_VM_HOOK_LOOP
-#endif
+        RUN_BACKGROUND_TASKS;
     }
 
     uint8_t byte;
diff --git a/ports/nrf/common-hal/audiobusio/I2SOut.c b/ports/nrf/common-hal/audiobusio/I2SOut.c
new file mode 100644
index 000000000..8be1fb2f8
--- /dev/null
+++ b/ports/nrf/common-hal/audiobusio/I2SOut.c
@@ -0,0 +1,70 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "common-hal/microcontroller/Pin.h"
+#include "common-hal/audiobusio/I2SOut.h"
+
+#include "py/obj.h"
+#include "py/runtime.h"
+
+void common_hal_audiobusio_i2sout_construct(audiobusio_i2sout_obj_t* self,
+        const mcu_pin_obj_t* bit_clock, const mcu_pin_obj_t* word_select,
+        const mcu_pin_obj_t* data, bool left_justified) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+bool common_hal_audiobusio_i2sout_deinited(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+void common_hal_audiobusio_i2sout_deinit(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+void common_hal_audiobusio_i2sout_play(audiobusio_i2sout_obj_t* self,
+                                       mp_obj_t sample, bool loop) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+void common_hal_audiobusio_i2sout_pause(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+void common_hal_audiobusio_i2sout_resume(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+bool common_hal_audiobusio_i2sout_get_paused(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+void common_hal_audiobusio_i2sout_stop(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
+
+bool common_hal_audiobusio_i2sout_get_playing(audiobusio_i2sout_obj_t* self) {
+    mp_raise_NotImplementedError(NULL);
+}
diff --git a/ports/nrf/common-hal/audiobusio/I2SOut.h b/ports/nrf/common-hal/audiobusio/I2SOut.h
new file mode 100644
index 000000000..01c944e72
--- /dev/null
+++ b/ports/nrf/common-hal/audiobusio/I2SOut.h
@@ -0,0 +1,36 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef MICROPY_INCLUDED_NRF_COMMON_HAL_AUDIOBUSIO_I2SOUT_H
+#define MICROPY_INCLUDED_NRF_COMMON_HAL_AUDIOBUSIO_I2SOUT_H
+
+#include "py/obj.h"
+
+typedef struct {
+    mp_obj_base_t base;
+} audiobusio_i2sout_obj_t;
+
+#endif // MICROPY_INCLUDED_NRF_COMMON_HAL_AUDIOBUSIO_I2SOUT_H
diff --git a/ports/nrf/common-hal/audiobusio/PDMIn.c b/ports/nrf/common-hal/audiobusio/PDMIn.c
new file mode 100644
index 000000000..a7f9c9d74
--- /dev/null
+++ b/ports/nrf/common-hal/audiobusio/PDMIn.c
@@ -0,0 +1,130 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "common-hal/audiobusio/PDMIn.h"
+#include "shared-bindings/microcontroller/Pin.h"
+
+#include "py/runtime.h"
+
+__attribute__((used))
+NRF_PDM_Type *nrf_pdm = NRF_PDM;
+
+static uint32_t dummy_buffer[4];
+
+void common_hal_audiobusio_pdmin_construct(audiobusio_pdmin_obj_t* self,
+                                           const mcu_pin_obj_t* clock_pin,
+                                           const mcu_pin_obj_t* data_pin,
+                                           uint32_t sample_rate,
+                                           uint8_t bit_depth,
+                                           bool mono,
+                                           uint8_t oversample) {
+    assert_pin_free(clock_pin);
+    assert_pin_free(data_pin);
+    claim_pin(clock_pin);
+    claim_pin(data_pin);
+
+    self->mono = mono;
+    self->clock_pin_number = clock_pin->number;
+    self->data_pin_number = data_pin->number;
+
+    if (sample_rate != 16000) {
+        mp_raise_ValueError(translate("only sample_rate=16000 is supported"));
+    }
+    if (bit_depth != 16) {
+        mp_raise_ValueError(translate("only bit_depth=16 is supported"));
+    }
+    nrf_pdm->PSEL.CLK = self->clock_pin_number;
+    nrf_pdm->PSEL.DIN = self->data_pin_number;
+    nrf_pdm->PDMCLKCTRL = PDM_PDMCLKCTRL_FREQ_Default; // For Ratio64
+    nrf_pdm->RATIO = PDM_RATIO_RATIO_Ratio64;
+    nrf_pdm->GAINL = PDM_GAINL_GAINL_DefaultGain;
+    nrf_pdm->GAINR = PDM_GAINR_GAINR_DefaultGain;
+    nrf_pdm->ENABLE = 1;
+
+    nrf_pdm->SAMPLE.PTR = (uintptr_t)&dummy_buffer;
+    nrf_pdm->SAMPLE.MAXCNT = 1;
+    nrf_pdm->TASKS_START = 1;
+}
+
+bool common_hal_audiobusio_pdmin_deinited(audiobusio_pdmin_obj_t* self) {
+    return !self->clock_pin_number;
+}
+
+void common_hal_audiobusio_pdmin_deinit(audiobusio_pdmin_obj_t* self) {
+    nrf_pdm->ENABLE = 0;
+
+    reset_pin_number(self->clock_pin_number);
+    self->clock_pin_number = 0;
+    reset_pin_number(self->data_pin_number);
+    self->data_pin_number = 0;
+}
+
+uint8_t common_hal_audiobusio_pdmin_get_bit_depth(audiobusio_pdmin_obj_t* self) {
+    return 16;
+}
+
+uint32_t common_hal_audiobusio_pdmin_get_sample_rate(audiobusio_pdmin_obj_t* self) {
+    return 16000;
+}
+
+uint32_t common_hal_audiobusio_pdmin_record_to_buffer(audiobusio_pdmin_obj_t* self,
+        uint16_t* output_buffer, uint32_t output_buffer_length) {
+    // Note: Adafruit's module has SELECT pulled to GND, which makes the DATA
+    // valid when the CLK is low, therefore it must be sampled on the rising edge.
+    if (self->mono) {
+        nrf_pdm->MODE = PDM_MODE_OPERATION_Stereo | PDM_MODE_EDGE_LeftRising;
+    } else {
+        nrf_pdm->MODE = PDM_MODE_OPERATION_Mono | PDM_MODE_EDGE_LeftRising;
+    }
+
+    // step 1. Redirect to real buffer
+    nrf_pdm->SAMPLE.PTR = (uintptr_t)output_buffer;
+    nrf_pdm->SAMPLE.MAXCNT = output_buffer_length;
+
+    // a delay is the safest simple way to ensure that the above requested sample has started
+    mp_hal_delay_us(200);
+    nrf_pdm->EVENTS_END = 0;
+
+    // step 2. Registers are double buffered, so pre-redirect back to dummy buffer
+    nrf_pdm->SAMPLE.PTR = (uintptr_t)&dummy_buffer;
+    nrf_pdm->SAMPLE.MAXCNT = 1;
+
+    // Step 3. wait for PDM to end
+    while (!nrf_pdm->EVENTS_END) {
+       MICROPY_VM_HOOK_LOOP;
+    }
+
+    // Step 4. They want unsigned
+    for (uint32_t i=0; i<output_buffer_length; i++) {
+        output_buffer[i] += 32768;
+    }
+
+    if (self->mono) {
+        return (output_buffer_length / 2) * 2;
+    } else {
+        return (output_buffer_length / 4) * 4;
+    }
+}
diff --git a/ports/nrf/common-hal/audiobusio/PDMIn.h b/ports/nrf/common-hal/audiobusio/PDMIn.h
new file mode 100644
index 000000000..d921e42ff
--- /dev/null
+++ b/ports/nrf/common-hal/audiobusio/PDMIn.h
@@ -0,0 +1,40 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef MICROPY_INCLUDED_NRF_COMMON_HAL_AUDIOBUSIO_AUDIOOUT_H
+#define MICROPY_INCLUDED_NRF_COMMON_HAL_AUDIOBUSIO_AUDIOOUT_H
+
+#include "common-hal/microcontroller/Pin.h"
+
+#include "py/obj.h"
+
+typedef struct {
+    mp_obj_base_t base;
+    uint8_t clock_pin_number, data_pin_number;
+    bool mono;
+} audiobusio_pdmin_obj_t;
+
+#endif
diff --git a/ports/nrf/common-hal/audiobusio/__init__.c b/ports/nrf/common-hal/audiobusio/__init__.c
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/ports/nrf/common-hal/audiobusio/__init__.c
diff --git a/ports/nrf/common-hal/bleio/Central.c b/ports/nrf/common-hal/bleio/Central.c
index d771437d6..3c5d97784 100644
--- a/ports/nrf/common-hal/bleio/Central.c
+++ b/ports/nrf/common-hal/bleio/Central.c
@@ -115,7 +115,7 @@ void common_hal_bleio_central_connect(bleio_central_obj_t *self, bleio_address_o
     }
 
     while (self->waiting_to_connect) {
-        MICROPY_VM_HOOK_LOOP;
+        RUN_BACKGROUND_TASKS;
     }
 
     if (self->conn_handle == BLE_CONN_HANDLE_INVALID) {
diff --git a/ports/nrf/common-hal/bleio/Characteristic.c b/ports/nrf/common-hal/bleio/Characteristic.c
index f8b6ce06c..45e8d2495 100644
--- a/ports/nrf/common-hal/bleio/Characteristic.c
+++ b/ports/nrf/common-hal/bleio/Characteristic.c
@@ -94,7 +94,7 @@ STATIC void characteristic_gatts_notify_indicate(uint16_t handle, uint16_t conn_
         // TX buffer is full
         // We could wait for an event indicating the write is complete, but just retrying is easier.
         if (err_code == NRF_ERROR_RESOURCES) {
-            MICROPY_VM_HOOK_LOOP;
+            RUN_BACKGROUND_TASKS;
             continue;
         }
 
@@ -118,7 +118,7 @@ STATIC void characteristic_gattc_read(bleio_characteristic_obj_t *characteristic
     }
 
     while (m_read_characteristic != NULL) {
-        MICROPY_VM_HOOK_LOOP;
+        RUN_BACKGROUND_TASKS;
     }
 
     ble_drv_remove_event_handler(characteristic_on_gattc_read_rsp_evt, characteristic);
@@ -258,7 +258,7 @@ void common_hal_bleio_characteristic_set_cccd(bleio_characteristic_obj_t *self,
         // Write without reponse will return NRF_ERROR_RESOURCES if too many writes are pending.
         if (err_code == NRF_ERROR_BUSY || err_code == NRF_ERROR_RESOURCES) {
             // We could wait for an event indicating the write is complete, but just retrying is easier.
-            MICROPY_VM_HOOK_LOOP;
+            RUN_BACKGROUND_TASKS;
             continue;
         }
 
diff --git a/ports/nrf/common-hal/bleio/CharacteristicBuffer.c b/ports/nrf/common-hal/bleio/CharacteristicBuffer.c
index a6d834d7d..64ab5e8a7 100644
--- a/ports/nrf/common-hal/bleio/CharacteristicBuffer.c
+++ b/ports/nrf/common-hal/bleio/CharacteristicBuffer.c
@@ -99,7 +99,7 @@ int common_hal_bleio_characteristic_buffer_read(bleio_characteristic_buffer_obj_
 
     // Wait for all bytes received or timeout
     while ( (ringbuf_count(&self->ringbuf) < len) && (ticks_ms - start_ticks < self->timeout_ms) ) {
-        MICROPY_VM_HOOK_LOOP;
+        RUN_BACKGROUND_TASKS;
         // Allow user to break out of a timeout with a KeyboardInterrupt.
         if ( mp_hal_is_interrupted() ) {
             return 0;
diff --git a/ports/nrf/common-hal/busio/UART.c b/ports/nrf/common-hal/busio/UART.c
index b9e9e5538..54a66ddbe 100644
--- a/ports/nrf/common-hal/busio/UART.c
+++ b/ports/nrf/common-hal/busio/UART.c
@@ -235,13 +235,11 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
 
     // Wait for all bytes received or timeout
     while ( (ringbuf_count(&self->rbuf) < len) && (ticks_ms - start_ticks < self->timeout_ms) ) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
+        RUN_BACKGROUND_TASKS;
         // Allow user to break out of a timeout with a KeyboardInterrupt.
         if ( mp_hal_is_interrupted() ) {
             return 0;
         }
-#endif
     }
 
     // prevent conflict with uart irq
@@ -271,9 +269,7 @@ size_t common_hal_busio_uart_write (busio_uart_obj_t *self, const uint8_t *data,
 
     // Wait for on-going transfer to complete
     while ( nrfx_uarte_tx_in_progress(self->uarte) && (ticks_ms - start_ticks < self->timeout_ms) ) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP
-#endif
+        RUN_BACKGROUND_TASKS;
     }
 
     // Time up
@@ -295,9 +291,7 @@ size_t common_hal_busio_uart_write (busio_uart_obj_t *self, const uint8_t *data,
     (*errcode) = 0;
 
     while ( nrfx_uarte_tx_in_progress(self->uarte) && (ticks_ms - start_ticks < self->timeout_ms) ) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP
-#endif
+        RUN_BACKGROUND_TASKS;
     }
 
     if ( !nrfx_is_in_ram(data) ) {
diff --git a/ports/nrf/common-hal/neopixel_write/__init__.c b/ports/nrf/common-hal/neopixel_write/__init__.c
index 78e0038e8..3b67778a6 100644
--- a/ports/nrf/common-hal/neopixel_write/__init__.c
+++ b/ports/nrf/common-hal/neopixel_write/__init__.c
@@ -200,9 +200,7 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
 
         // But we have to wait for the flag to be set.
         while ( !nrf_pwm_event_check(pwm, NRF_PWM_EVENT_SEQEND0) ) {
-#ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-#endif
+            RUN_BACKGROUND_TASKS;
         }
 
         // Before leave we clear the flag for the event.
diff --git a/ports/nrf/common-hal/pulseio/PulseOut.c b/ports/nrf/common-hal/pulseio/PulseOut.c
index be5deca9f..d0433247a 100644
--- a/ports/nrf/common-hal/pulseio/PulseOut.c
+++ b/ports/nrf/common-hal/pulseio/PulseOut.c
@@ -155,9 +155,7 @@ void common_hal_pulseio_pulseout_send(pulseio_pulseout_obj_t* self, uint16_t* pu
     while(pulse_array_index < length) {
         // Do other things while we wait. The interrupts will handle sending the
         // signal.
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
     }
 
     nrfx_timer_disable(timer);
diff --git a/ports/nrf/device/nrf52/startup_nrf52840.c b/ports/nrf/device/nrf52/startup_nrf52840.c
index 30634a1b5..8e1c36012 100644
--- a/ports/nrf/device/nrf52/startup_nrf52840.c
+++ b/ports/nrf/device/nrf52/startup_nrf52840.c
@@ -116,7 +116,7 @@ void CRYPTOCELL_IRQHandler       (void) __attribute__ ((weak, alias("Default_Han
 void SPIM3_IRQHandler            (void) __attribute__ ((weak, alias("Default_Handler")));
 void PWM3_IRQHandler             (void) __attribute__ ((weak, alias("Default_Handler")));
 
-const func __Vectors[] __attribute__ ((section(".isr_vector"))) = {
+const func __Vectors[] __attribute__ ((used, section(".isr_vector"))) = {
     (func)&_estack,
     Reset_Handler,
     NMI_Handler,
diff --git a/ports/nrf/mpconfigport.mk b/ports/nrf/mpconfigport.mk
index 57879bbaa..55920b3f4 100644
--- a/ports/nrf/mpconfigport.mk
+++ b/ports/nrf/mpconfigport.mk
@@ -14,9 +14,7 @@ LONGINT_IMPL = MPZ
 CIRCUITPY_AUDIOCORE = 1
 CIRCUITPY_AUDIOIO = 0
 CIRCUITPY_AUDIOPWMIO = 1
-
-# No I2S yet.
-CIRCUITPY_AUDIOBUSIO = 0
+CIRCUITPY_AUDIOBUSIO = 1
 
 # No I2CSlave implementation
 CIRCUITPY_I2CSLAVE = 0
diff --git a/ports/nrf/mphalport.c b/ports/nrf/mphalport.c
index 7d9463d0b..bcd9fb114 100644
--- a/ports/nrf/mphalport.c
+++ b/ports/nrf/mphalport.c
@@ -39,9 +39,7 @@ void mp_hal_delay_ms(mp_uint_t delay) {
     uint64_t start_tick = ticks_ms;
     uint64_t duration = 0;
     while (duration < delay) {
-        #ifdef MICROPY_VM_HOOK_LOOP
-            MICROPY_VM_HOOK_LOOP
-        #endif
+        RUN_BACKGROUND_TASKS;
         // Check to see if we've been CTRL-Ced by autoreload or the user.
         if(MP_STATE_VM(mp_pending_exception) == MP_OBJ_FROM_PTR(&MP_STATE_VM(mp_kbd_exception)) ||
            MP_STATE_VM(mp_pending_exception) == MP_OBJ_FROM_PTR(&MP_STATE_VM(mp_reload_exception))) {
diff --git a/ports/nrf/sd_mutex.c b/ports/nrf/sd_mutex.c
index 7682ffa62..b3162e6af 100644
--- a/ports/nrf/sd_mutex.c
+++ b/ports/nrf/sd_mutex.c
@@ -37,9 +37,7 @@ void sd_mutex_acquire_check(nrf_mutex_t* p_mutex) {
 
 void sd_mutex_acquire_wait(nrf_mutex_t* p_mutex) {
     while (sd_mutex_acquire(p_mutex) == NRF_ERROR_SOC_MUTEX_ALREADY_TAKEN) {
-#ifdef MICROPY_VM_HOOK_LOOP
-    MICROPY_VM_HOOK_LOOP
-#endif
+        RUN_BACKGROUND_TASKS;
     }
 }
 
diff --git a/py/circuitpy_mpconfig.h b/py/circuitpy_mpconfig.h
index 1dbca8c61..393b7600c 100644
--- a/py/circuitpy_mpconfig.h
+++ b/py/circuitpy_mpconfig.h
@@ -596,8 +596,8 @@ extern const struct _mp_obj_module_t ustack_module;
       WIZNET_MODULE \
     PEW_MODULE \
     PIXELBUF_MODULE \
-    PULSEIO_MODULE \
     PS2IO_MODULE \
+    PULSEIO_MODULE \
     RANDOM_MODULE \
     RE_MODULE \
     ROTARYIO_MODULE \
@@ -645,6 +645,7 @@ extern const struct _mp_obj_module_t ustack_module;
     NETWORK_ROOT_POINTERS \
 
 void run_background_tasks(void);
+#define RUN_BACKGROUND_TASKS (run_background_tasks())
 
 // TODO: Used in wiznet5k driver, but may not be needed in the long run.
 #define MICROPY_THREAD_YIELD()
diff --git a/py/circuitpy_mpconfig.mk b/py/circuitpy_mpconfig.mk
index 7469fbf3f..949cd1d18 100644
--- a/py/circuitpy_mpconfig.mk
+++ b/py/circuitpy_mpconfig.mk
@@ -74,6 +74,12 @@ CIRCUITPY_AUDIOIO = $(CIRCUITPY_FULL_BUILD)
 endif
 CFLAGS += -DCIRCUITPY_AUDIOIO=$(CIRCUITPY_AUDIOIO)
 
+ifndef CIRCUITPY_AUDIOIO_COMPAT
+CIRCUITPY_AUDIOIO_COMPAT = $(CIRCUITPY_AUDIOIO)
+endif
+CFLAGS += -DCIRCUITPY_AUDIOIO_COMPAT=$(CIRCUITPY_AUDIOIO_COMPAT)
+
+
 ifndef CIRCUITPY_AUDIOPWMIO
 CIRCUITPY_AUDIOPWMIO = 0
 endif
diff --git a/shared-bindings/_stage/__init__.c b/shared-bindings/_stage/__init__.c
index 485fa80c5..6096f6b6d 100644
--- a/shared-bindings/_stage/__init__.c
+++ b/shared-bindings/_stage/__init__.c
@@ -96,9 +96,7 @@ STATIC mp_obj_t stage_render(size_t n_args, const mp_obj_t *args) {
     }
 
     while (!displayio_display_begin_transaction(display)) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
-#endif
+        RUN_BACKGROUND_TASKS;
     }
     displayio_area_t area;
     area.x1 = x0;
diff --git a/shared-bindings/audiocore/WaveFile.c b/shared-bindings/audiocore/WaveFile.c
index edb190d3a..1b3a94ff3 100644
--- a/shared-bindings/audiocore/WaveFile.c
+++ b/shared-bindings/audiocore/WaveFile.c
@@ -39,13 +39,16 @@
 //| ========================================================
 //|
 //| A .wav file prepped for audio playback. Only mono and stereo files are supported. Samples must
-//| be 8 bit unsigned or 16 bit signed.
+//| be 8 bit unsigned or 16 bit signed. If a buffer is provided, it will be used instead of allocating
+//| an internal buffer.
 //|
-//| .. class:: WaveFile(file)
+//| .. class:: WaveFile(file[, buffer])
 //|
 //|   Load a .wav file for playback with `audioio.AudioOut` or `audiobusio.I2SOut`.
 //|
 //|   :param typing.BinaryIO file: Already opened wave file
+//|   :param bytearray buffer: Optional pre-allocated buffer, that will be split in half and used for double-buffering of the data. If not provided, two 512 byte buffers are allocated internally.
+//|
 //|
 //|   Playing a wave file from flash::
 //|
@@ -69,15 +72,23 @@
 //|     print("stopped")
 //|
 STATIC mp_obj_t audioio_wavefile_make_new(const mp_obj_type_t *type, size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
-    mp_arg_check_num(n_args, kw_args, 1, 1, false);
+    mp_arg_check_num(n_args, kw_args, 1, 2, false);
 
     audioio_wavefile_obj_t *self = m_new_obj(audioio_wavefile_obj_t);
     self->base.type = &audioio_wavefile_type;
-    if (MP_OBJ_IS_TYPE(args[0], &mp_type_fileio)) {
-        common_hal_audioio_wavefile_construct(self, MP_OBJ_TO_PTR(args[0]));
-    } else {
+    if (!MP_OBJ_IS_TYPE(args[0], &mp_type_fileio)) {
         mp_raise_TypeError(translate("file must be a file opened in byte mode"));
     }
+    uint8_t *buffer = NULL;
+    size_t buffer_size = 0;
+    if (n_args >= 2) {
+        mp_buffer_info_t bufinfo;
+        mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
+        buffer = bufinfo.buf;
+        buffer_size = bufinfo.len;
+    }
+    common_hal_audioio_wavefile_construct(self, MP_OBJ_TO_PTR(args[0]),
+                                          buffer, buffer_size);
 
     return MP_OBJ_FROM_PTR(self);
 }
diff --git a/shared-bindings/audiocore/WaveFile.h b/shared-bindings/audiocore/WaveFile.h
index d2572318b..f4a172319 100644
--- a/shared-bindings/audiocore/WaveFile.h
+++ b/shared-bindings/audiocore/WaveFile.h
@@ -35,7 +35,7 @@
 extern const mp_obj_type_t audioio_wavefile_type;
 
 void common_hal_audioio_wavefile_construct(audioio_wavefile_obj_t* self,
-    pyb_file_obj_t* file);
+    pyb_file_obj_t* file, uint8_t *buffer, size_t buffer_size);
 
 void common_hal_audioio_wavefile_deinit(audioio_wavefile_obj_t* self);
 bool common_hal_audioio_wavefile_deinited(audioio_wavefile_obj_t* self);
diff --git a/shared-bindings/audioio/__init__.c b/shared-bindings/audioio/__init__.c
index 3fecf2708..bd771dda2 100644
--- a/shared-bindings/audioio/__init__.c
+++ b/shared-bindings/audioio/__init__.c
@@ -33,6 +33,12 @@
 #include "shared-bindings/audioio/__init__.h"
 #include "shared-bindings/audioio/AudioOut.h"
 
+#ifdef CIRCUITPY_AUDIOIO_COMPAT
+#include "shared-bindings/audiocore/Mixer.h"
+#include "shared-bindings/audiocore/RawSample.h"
+#include "shared-bindings/audiocore/WaveFile.h"
+#endif
+
 //| :mod:`audioio` --- Support for audio input and output
 //| ======================================================
 //|
@@ -57,10 +63,19 @@
 //| Since CircuitPython 5, `Mixer`, `RawSample` and `WaveFile` are moved
 //| to :mod:`audiocore`.
 //|
+//| For compatibility with CircuitPython 4.x, some builds allow the items in
+//| `audiocore` to be imported from `audioio`.  This will be removed for all
+//| boards in a future build of CicuitPython.
+//|
 
 STATIC const mp_rom_map_elem_t audioio_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_audioio) },
     { MP_ROM_QSTR(MP_QSTR_AudioOut), MP_ROM_PTR(&audioio_audioout_type) },
+#ifdef CIRCUITPY_AUDIOIO_COMPAT
+    { MP_ROM_QSTR(MP_QSTR_Mixer), MP_ROM_PTR(&audioio_mixer_type) },
+    { MP_ROM_QSTR(MP_QSTR_RawSample), MP_ROM_PTR(&audioio_rawsample_type) },
+    { MP_ROM_QSTR(MP_QSTR_WaveFile), MP_ROM_PTR(&audioio_wavefile_type) },
+#endif
 };
 
 STATIC MP_DEFINE_CONST_DICT(audioio_module_globals, audioio_module_globals_table);
diff --git a/shared-bindings/displayio/FourWire.c b/shared-bindings/displayio/FourWire.c
index af64a2028..0d41359ee 100644
--- a/shared-bindings/displayio/FourWire.c
+++ b/shared-bindings/displayio/FourWire.c
@@ -119,9 +119,7 @@ STATIC mp_obj_t displayio_fourwire_obj_send(mp_obj_t self, mp_obj_t command_obj,
 
     // Wait for display bus to be available.
     while (!common_hal_displayio_fourwire_begin_transaction(self)) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
-#endif
+        RUN_BACKGROUND_TASKS;
     }
     common_hal_displayio_fourwire_send(self, true, &command, 1);
     common_hal_displayio_fourwire_send(self, false, ((uint8_t*) bufinfo.buf), bufinfo.len);
diff --git a/shared-bindings/displayio/I2CDisplay.c b/shared-bindings/displayio/I2CDisplay.c
index 1f74e8c9e..9ef989d71 100644
--- a/shared-bindings/displayio/I2CDisplay.c
+++ b/shared-bindings/displayio/I2CDisplay.c
@@ -111,9 +111,7 @@ STATIC mp_obj_t displayio_i2cdisplay_obj_send(mp_obj_t self, mp_obj_t command_ob
 
     // Wait for display bus to be available.
     while (!common_hal_displayio_i2cdisplay_begin_transaction(self)) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
-#endif
+        RUN_BACKGROUND_TASKS;
     }
     uint8_t full_command[bufinfo.len + 1];
     full_command[0] = command;
diff --git a/shared-bindings/displayio/ParallelBus.c b/shared-bindings/displayio/ParallelBus.c
index 00a96d230..c29c79fff 100644
--- a/shared-bindings/displayio/ParallelBus.c
+++ b/shared-bindings/displayio/ParallelBus.c
@@ -122,9 +122,7 @@ STATIC mp_obj_t displayio_parallelbus_obj_send(mp_obj_t self, mp_obj_t command_o
 
     // Wait for display bus to be available.
     while (!common_hal_displayio_parallelbus_begin_transaction(self)) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
-#endif
+        RUN_BACKGROUND_TASKS;
     }
     common_hal_displayio_parallelbus_send(self, true, &command, 1);
     common_hal_displayio_parallelbus_send(self, false, ((uint8_t*) bufinfo.buf), bufinfo.len);
diff --git a/shared-bindings/i2cslave/I2CSlave.c b/shared-bindings/i2cslave/I2CSlave.c
index 2598accbb..c98ea52e0 100644
--- a/shared-bindings/i2cslave/I2CSlave.c
+++ b/shared-bindings/i2cslave/I2CSlave.c
@@ -182,7 +182,7 @@ STATIC mp_obj_t i2cslave_i2c_slave_request(size_t n_args, const mp_obj_t *pos_ar
         bool is_read;
         bool is_restart;
 
-        MICROPY_VM_HOOK_LOOP
+        RUN_BACKGROUND_TASKS;
         if (mp_hal_is_interrupted()) {
             return mp_const_none;
         }
@@ -337,7 +337,7 @@ STATIC mp_obj_t i2cslave_i2c_slave_request_read(size_t n_args, const mp_obj_t *p
     uint8_t *buffer = NULL;
     uint64_t timeout_end = common_hal_time_monotonic() + 10 * 1000;
     while (common_hal_time_monotonic() < timeout_end) {
-        MICROPY_VM_HOOK_LOOP
+        RUN_BACKGROUND_TASKS;
         if (mp_hal_is_interrupted()) {
             break;
         }
@@ -382,7 +382,7 @@ STATIC mp_obj_t i2cslave_i2c_slave_request_write(mp_obj_t self_in, mp_obj_t buf_
     mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_READ);
 
     for (size_t i = 0; i < bufinfo.len; i++) {
-        MICROPY_VM_HOOK_LOOP
+        RUN_BACKGROUND_TASKS;
         if (mp_hal_is_interrupted()) {
             break;
         }
diff --git a/shared-bindings/time/__init__.c b/shared-bindings/time/__init__.c
index f34cb9c46..2654de09a 100644
--- a/shared-bindings/time/__init__.c
+++ b/shared-bindings/time/__init__.c
@@ -236,9 +236,16 @@ STATIC mp_obj_t time_localtime(size_t n_args, const mp_obj_t *args) {
         return rtc_get_time_source_time();
     }
 
-    mp_int_t secs = mp_obj_int_get_checked(args[0]);
-    if (secs < EPOCH1970_EPOCH2000_DIFF_SECS)
+    mp_obj_t arg = args[0];
+    if (mp_obj_is_float(arg)) {
+        arg = mp_obj_new_int_from_float(mp_obj_get_float(arg));
+    }
+
+    mp_int_t secs = mp_obj_get_int(arg);
+
+    if (secs < EPOCH1970_EPOCH2000_DIFF_SECS) {
         mp_raise_msg(&mp_type_OverflowError, translate("timestamp out of range for platform time_t"));
+    }
 
     timeutils_struct_time_t tm;
     timeutils_seconds_since_epoch_to_struct_time(secs, &tm);
@@ -270,8 +277,9 @@ STATIC mp_obj_t time_mktime(mp_obj_t t) {
         mp_raise_TypeError(translate("function takes exactly 9 arguments"));
     }
 
-    if (mp_obj_get_int(elem[0]) < 2000)
+    if (mp_obj_get_int(elem[0]) < 2000) {
         mp_raise_msg(&mp_type_OverflowError, translate("timestamp out of range for platform time_t"));
+    }
 
     mp_uint_t secs = timeutils_mktime(mp_obj_get_int(elem[0]), mp_obj_get_int(elem[1]), mp_obj_get_int(elem[2]),
                                       mp_obj_get_int(elem[3]), mp_obj_get_int(elem[4]), mp_obj_get_int(elem[5]));
diff --git a/shared-module/audiocore/WaveFile.c b/shared-module/audiocore/WaveFile.c
index 810d9c33b..df5d4b61d 100644
--- a/shared-module/audiocore/WaveFile.c
+++ b/shared-module/audiocore/WaveFile.c
@@ -46,7 +46,9 @@ struct wave_format_chunk {
 };
 
 void common_hal_audioio_wavefile_construct(audioio_wavefile_obj_t* self,
-                                           pyb_file_obj_t* file) {
+                                           pyb_file_obj_t* file,
+                                           uint8_t *buffer,
+                                           size_t buffer_size) {
     // Load the wave
     self->file = file;
     uint8_t chunk_header[16];
@@ -84,7 +86,6 @@ void common_hal_audioio_wavefile_construct(audioio_wavefile_obj_t* self,
     }
     // Get the sample_rate
     self->sample_rate = format.sample_rate;
-    self->len = 256;
     self->channel_count = format.num_channels;
     self->bits_per_sample = format.bits_per_sample;
 
@@ -111,21 +112,31 @@ void common_hal_audioio_wavefile_construct(audioio_wavefile_obj_t* self,
 
     // Try to allocate two buffers, one will be loaded from file and the other
     // DMAed to DAC.
-    self->buffer = m_malloc(self->len, false);
-    if (self->buffer == NULL) {
-        common_hal_audioio_wavefile_deinit(self);
-        mp_raise_msg(&mp_type_MemoryError, translate("Couldn't allocate first buffer"));
-    }
+    if (buffer_size) {
+        self->len = buffer_size / 2;
+        self->buffer = buffer;
+        self->second_buffer = buffer + self->len;
+    } else {
+        self->len = 256;
+        self->buffer = m_malloc(self->len, false);
+        if (self->buffer == NULL) {
+            common_hal_audioio_wavefile_deinit(self);
+            mp_raise_msg(&mp_type_MemoryError,
+                         translate("Couldn't allocate first buffer"));
+        }
 
-    self->second_buffer = m_malloc(self->len, false);
-    if (self->second_buffer == NULL) {
-        common_hal_audioio_wavefile_deinit(self);
-        mp_raise_msg(&mp_type_MemoryError, translate("Couldn't allocate second buffer"));
+        self->second_buffer = m_malloc(self->len, false);
+        if (self->second_buffer == NULL) {
+            common_hal_audioio_wavefile_deinit(self);
+            mp_raise_msg(&mp_type_MemoryError,
+                         translate("Couldn't allocate second buffer"));
+        }
     }
 }
 
 void common_hal_audioio_wavefile_deinit(audioio_wavefile_obj_t* self) {
     self->buffer = NULL;
+    self->second_buffer = NULL;
 }
 
 bool common_hal_audioio_wavefile_deinited(audioio_wavefile_obj_t* self) {
diff --git a/shared-module/displayio/Display.c b/shared-module/displayio/Display.c
index aa36ee982..c23c66b8b 100644
--- a/shared-module/displayio/Display.c
+++ b/shared-module/displayio/Display.c
@@ -85,9 +85,7 @@ void common_hal_displayio_display_construct(displayio_display_obj_t* self,
 
     uint32_t i = 0;
     while (!self->begin_transaction(self->bus)) {
-#ifdef MICROPY_VM_HOOK_LOOP
-        MICROPY_VM_HOOK_LOOP ;
-#endif
+        RUN_BACKGROUND_TASKS;
     }
     while (i < init_sequence_len) {
         uint8_t *cmd = init_sequence + i;
@@ -242,7 +240,7 @@ int32_t common_hal_displayio_display_wait_for_frame(displayio_display_obj_t* sel
     uint64_t last_refresh = self->last_refresh;
     // Don't try to refresh if we got an exception.
     while (last_refresh == self->last_refresh && MP_STATE_VM(mp_pending_exception) == NULL) {
-        MICROPY_VM_HOOK_LOOP
+        RUN_BACKGROUND_TASKS;
     }
     return 0;
 }
diff --git a/tools/check_translations.py b/tools/check_translations.py
index 4bea040bf..7c008d3da 100644
--- a/tools/check_translations.py
+++ b/tools/check_translations.py
@@ -16,8 +16,10 @@ for po_filename in po_filenames:
     po_file = polib.pofile(po_filename)
     po_ids = set([x.msgid for x in po_file])
 
-    if all_ids - po_ids:
+    missing = all_ids - po_ids
+    if missing:
         print("Missing message id. Please run `make translate`")
+        print(missing)
         sys.exit(-1)
     else:
         print("ok")