diff --git a/ports/nrf/common-hal/audiobusio/I2SOut.c b/ports/nrf/common-hal/audiobusio/I2SOut.c
index ead92b0000..65c153e1a0 100644
--- a/ports/nrf/common-hal/audiobusio/I2SOut.c
+++ b/ports/nrf/common-hal/audiobusio/I2SOut.c
@@ -283,6 +283,9 @@ void common_hal_audiobusio_i2sout_play(audiobusio_i2sout_obj_t* self,
     i2s_buffer_fill(self);
 
     NRF_I2S->RXTXD.MAXCNT = self->buffer_length / 4;
+    // Turn on the interrupt to the NVIC but not within the NVIC itself. This will wake the CPU and
+    // keep it awake until it is serviced without triggering an interrupt handler.
+    NRF_I2S->INTENSET = I2S_INTENSET_TXPTRUPD_Msk;
     NRF_I2S->ENABLE = I2S_ENABLE_ENABLE_Enabled;
 
     NRF_I2S->TASKS_START = 1;
@@ -305,6 +308,7 @@ bool common_hal_audiobusio_i2sout_get_paused(audiobusio_i2sout_obj_t* self) {
 void common_hal_audiobusio_i2sout_stop(audiobusio_i2sout_obj_t* self) {
     NRF_I2S->TASKS_STOP = 1;
     self->stopping = true;
+    NRF_I2S->INTENCLR = I2S_INTENSET_TXPTRUPD_Msk;
 }
 
 bool common_hal_audiobusio_i2sout_get_playing(audiobusio_i2sout_obj_t* self) {
@@ -316,7 +320,7 @@ bool common_hal_audiobusio_i2sout_get_playing(audiobusio_i2sout_obj_t* self) {
 }
 
 void i2s_background(void) {
-    if (NRF_I2S->EVENTS_TXPTRUPD) {
+    if (NVIC_GetPendingIRQ(I2S_IRQn) && NRF_I2S->EVENTS_TXPTRUPD) {
         NRF_I2S->EVENTS_TXPTRUPD = 0;
         if (instance) {
             i2s_buffer_fill(instance);
@@ -328,6 +332,7 @@ void i2s_background(void) {
 
 void i2s_reset(void) {
     NRF_I2S->TASKS_STOP = 1;
+    NRF_I2S->INTENCLR = I2S_INTENSET_TXPTRUPD_Msk;
     NRF_I2S->ENABLE = I2S_ENABLE_ENABLE_Disabled;
     NRF_I2S->PSEL.MCK = 0xFFFFFFFF;
     NRF_I2S->PSEL.SCK = 0xFFFFFFFF;
diff --git a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c
index 7b99901d5c..239b491351 100644
--- a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c
+++ b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c
@@ -72,6 +72,8 @@ STATIC void activate_audiopwmout_obj(audiopwmio_pwmaudioout_obj_t *self) {
     }
 }
 STATIC void deactivate_audiopwmout_obj(audiopwmio_pwmaudioout_obj_t *self) {
+    // Turn off the interrupts to the CPU.
+    self->pwm->INTENCLR = PWM_INTENSET_SEQSTARTED0_Msk | PWM_INTENSET_SEQSTARTED1_Msk;
     for (size_t i=0; i < MP_ARRAY_SIZE(active_audio); i++) {
         if (active_audio[i] == self) {
             active_audio[i] = NULL;
@@ -149,6 +151,14 @@ STATIC void audiopwmout_background_obj(audiopwmio_pwmaudioout_obj_t *self) {
 }
 
 void audiopwmout_background() {
+    // Check the NVIC first because it is part of the CPU and fast to read.
+    if (!NVIC_GetPendingIRQ(PWM0_IRQn) &&
+        !NVIC_GetPendingIRQ(PWM1_IRQn) &&
+        !NVIC_GetPendingIRQ(PWM2_IRQn) &&
+        !NVIC_GetPendingIRQ(PWM3_IRQn)) {
+        return;
+    }
+    // Check our objects because the PWM could be active for some other reason.
     for (size_t i=0; i < MP_ARRAY_SIZE(active_audio); i++) {
         if (!active_audio[i]) continue;
         audiopwmout_background_obj(active_audio[i]);
@@ -260,6 +270,9 @@ void common_hal_audiopwmio_pwmaudioout_play(audiopwmio_pwmaudioout_obj_t* self,
     self->pwm->EVENTS_SEQEND[0] = 0;
     self->pwm->EVENTS_SEQEND[1] = 0;
     self->pwm->EVENTS_STOPPED = 0;
+    // Enable the SEQSTARTED interrupts so that they wake the CPU and keep it awake until serviced.
+    // We don't enable them in the NVIC because we don't actually want an interrupt routine to run.
+    self->pwm->INTENSET = PWM_INTENSET_SEQSTARTED0_Msk | PWM_INTENSET_SEQSTARTED1_Msk;
     self->pwm->TASKS_SEQSTART[0] = 1;
     self->playing = true;
     self->paused = false;
diff --git a/ports/nrf/supervisor/internal_flash.c b/ports/nrf/supervisor/internal_flash.c
index a44f047ff6..737bab2036 100644
--- a/ports/nrf/supervisor/internal_flash.c
+++ b/ports/nrf/supervisor/internal_flash.c
@@ -67,7 +67,7 @@ uint32_t supervisor_flash_get_block_count(void) {
     return CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE / FILESYSTEM_BLOCK_SIZE ;
 }
 
-void supervisor_flash_flush(void) {
+void port_internal_flash_flush(void) {
     if (_flash_page_addr == NO_CACHE) return;
 
     // Skip if data is the same
diff --git a/supervisor/flash.h b/supervisor/flash.h
index 0a124353e6..a8a77bf040 100644
--- a/supervisor/flash.h
+++ b/supervisor/flash.h
@@ -34,7 +34,7 @@
 #ifdef EXTERNAL_FLASH_DEVICE_COUNT
 #include "supervisor/shared/external_flash/external_flash.h"
 #else
-#include "supervisor/internal_flash.h"
+#include "supervisor/shared/internal_flash.h"
 #endif
 
 void supervisor_flash_init(void);
diff --git a/supervisor/shared/external_flash/external_flash.c b/supervisor/shared/external_flash/external_flash.c
index 9d38c07d89..69eeec43d1 100644
--- a/supervisor/shared/external_flash/external_flash.c
+++ b/supervisor/shared/external_flash/external_flash.c
@@ -23,11 +23,12 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-#include "external_flash.h"
+#include "supervisor/shared/external_flash/external_flash.h"
 
 #include <stdint.h>
 #include <string.h>
 
+#include "supervisor/flash.h"
 #include "supervisor/spi_flash_api.h"
 #include "supervisor/shared/external_flash/common_commands.h"
 #include "extmod/vfs.h"
@@ -451,7 +452,7 @@ static void spi_flash_flush_keep_cache(bool keep_cache) {
     #endif
 }
 
-void supervisor_flash_flush(void) {
+void supervisor_external_flash_flush(void) {
     spi_flash_flush_keep_cache(true);
 }
 
diff --git a/supervisor/shared/external_flash/external_flash.h b/supervisor/shared/external_flash/external_flash.h
index 72b619a2a8..db5c677eb0 100644
--- a/supervisor/shared/external_flash/external_flash.h
+++ b/supervisor/shared/external_flash/external_flash.h
@@ -45,4 +45,6 @@
 #define SPI_FLASH_MAX_BAUDRATE 8000000
 #endif
 
+void supervisor_external_flash_flush(void);
+
 #endif  // MICROPY_INCLUDED_SUPERVISOR_SHARED_EXTERNAL_FLASH_EXTERNAL_FLASH_H
diff --git a/supervisor/shared/flash.c b/supervisor/shared/flash.c
index 6b1f24b4bc..e0bf83490c 100644
--- a/supervisor/shared/flash.c
+++ b/supervisor/shared/flash.c
@@ -28,6 +28,7 @@
 #include "extmod/vfs_fat.h"
 #include "py/runtime.h"
 #include "lib/oofatfs/ff.h"
+#include "supervisor/shared/tick.h"
 
 #define VFS_INDEX 0
 
@@ -110,6 +111,8 @@ mp_uint_t flash_read_blocks(uint8_t *dest, uint32_t block_num, uint32_t num_bloc
     return supervisor_flash_read_blocks(dest, block_num - PART1_START_BLOCK, num_blocks);
 }
 
+volatile bool filesystem_dirty;
+
 mp_uint_t flash_write_blocks(const uint8_t *src, uint32_t block_num, uint32_t num_blocks) {
     if (block_num == 0) {
         if (num_blocks > 1) {
@@ -118,10 +121,26 @@ mp_uint_t flash_write_blocks(const uint8_t *src, uint32_t block_num, uint32_t nu
         // can't write MBR, but pretend we did
         return 0;
     } else {
+        if (!filesystem_dirty) {
+            // Turn on ticks so that we can flush after a period of time elapses.
+            supervisor_enable_tick();
+            filesystem_dirty = true;
+        }
         return supervisor_flash_write_blocks(src, block_num - PART1_START_BLOCK, num_blocks);
     }
 }
 
+void supervisor_flash_flush(void) {
+    #if INTERNAL_FLASH_FILESYSTEM
+    port_internal_flash_flush();
+    #else
+    supervisor_external_flash_flush();
+    #endif
+    // Turn off ticks now that our filesystem has been flushed.
+    supervisor_disable_tick();
+    filesystem_dirty = false;
+}
+
 STATIC mp_obj_t supervisor_flash_obj_readblocks(mp_obj_t self, mp_obj_t block_num, mp_obj_t buf) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_WRITE);
diff --git a/supervisor/shared/internal_flash.h b/supervisor/shared/internal_flash.h
new file mode 100644
index 0000000000..80257a2901
--- /dev/null
+++ b/supervisor/shared/internal_flash.h
@@ -0,0 +1,33 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 Scott Shawcroft, for Adafruit Industries LLC
+ *
+ * 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_SUPERVISOR_SHARED_INTERNAL_FLASH_H
+#define MICROPY_INCLUDED_SUPERVISOR_SHARED_INTERNAL_FLASH_H
+
+#include "supervisor/internal_flash.h" // This is per-port.
+
+void port_internal_flash_flush(void);
+
+#endif  // MICROPY_INCLUDED_SUPERVISOR_SHARED_INTERNAL_FLASH_H