Merge remote-tracking branch 'adafruit/master' into ble-pairing

16 files changed, 653 insertions, 58 deletions

diff --git a/ports/nrf/background.c b/ports/nrf/background.c
index 9c4f3ab27..453bc96df 100644
--- a/ports/nrf/background.c
+++ b/ports/nrf/background.c
@@ -33,6 +33,10 @@
 #include "shared-module/displayio/__init__.h"
 #endif
 
+#if CIRCUITPY_AUDIOPWMIO
+#include "common-hal/audiopwmio/PWMAudioOut.h"
+#endif
+
 static bool running_background_tasks = false;
 
 void background_tasks_reset(void) {
@@ -47,6 +51,9 @@ void run_background_tasks(void) {
     running_background_tasks = true;
     filesystem_background();
     usb_background();
+#if CIRCUITPY_AUDIOPWMIO
+    audiopwmout_background();
+#endif
 
     #if CIRCUITPY_DISPLAYIO
     displayio_refresh_displays();
diff --git a/ports/nrf/boards/feather_nrf52840_express/mpconfigboard.h b/ports/nrf/boards/feather_nrf52840_express/mpconfigboard.h
index e1f43e3c9..70ccffc3f 100644
--- a/ports/nrf/boards/feather_nrf52840_express/mpconfigboard.h
+++ b/ports/nrf/boards/feather_nrf52840_express/mpconfigboard.h
@@ -27,8 +27,6 @@
 
 #include "nrfx/hal/nrf_gpio.h"
 
-#define FEATHER52840
-
 #define MICROPY_HW_BOARD_NAME       "Adafruit Feather nRF52840 Express"
 #define MICROPY_HW_MCU_NAME         "nRF52840"
 #define MICROPY_PY_SYS_PLATFORM     "Feather52840Express"
diff --git a/ports/nrf/boards/metro_nrf52840_express/board.c b/ports/nrf/boards/metro_nrf52840_express/board.c
new file mode 100644
index 000000000..4421970ee
--- /dev/null
+++ b/ports/nrf/boards/metro_nrf52840_express/board.c
@@ -0,0 +1,38 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft 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 "boards/board.h"
+
+void board_init(void) {
+}
+
+bool board_requests_safe_mode(void) {
+  return false;
+}
+
+void reset_board(void) {
+
+}
diff --git a/ports/nrf/boards/metro_nrf52840_express/mpconfigboard.h b/ports/nrf/boards/metro_nrf52840_express/mpconfigboard.h
new file mode 100644
index 000000000..520eef90d
--- /dev/null
+++ b/ports/nrf/boards/metro_nrf52840_express/mpconfigboard.h
@@ -0,0 +1,73 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Glenn Ruben Bakke
+ * Copyright (c) 2018 Dan Halbert 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 "nrfx/hal/nrf_gpio.h"
+
+#define MICROPY_HW_BOARD_NAME       "Adafruit Metro nRF52840 Express"
+#define MICROPY_HW_MCU_NAME         "nRF52840"
+#define MICROPY_PY_SYS_PLATFORM     "Metro52840Express"
+
+#define FLASH_SIZE                  (0x100000)
+#define FLASH_PAGE_SIZE             (4096)
+
+#define MICROPY_HW_NEOPIXEL         (&pin_P0_13)
+
+#define MICROPY_HW_LED_STATUS       (&pin_P1_13)
+
+#if QSPI_FLASH_FILESYSTEM
+#define MICROPY_QSPI_DATA0                NRF_GPIO_PIN_MAP(0, 17)
+#define MICROPY_QSPI_DATA1                NRF_GPIO_PIN_MAP(0, 23)
+#define MICROPY_QSPI_DATA2                NRF_GPIO_PIN_MAP(0, 22)
+#define MICROPY_QSPI_DATA3                NRF_GPIO_PIN_MAP(0, 21)
+#define MICROPY_QSPI_SCK                  NRF_GPIO_PIN_MAP(0, 19)
+#define MICROPY_QSPI_CS                   NRF_GPIO_PIN_MAP(0, 20)
+#endif
+
+#if SPI_FLASH_FILESYSTEM
+#define SPI_FLASH_MOSI_PIN &pin_P0_17
+#define SPI_FLASH_MISO_PIN &pin_P0_23
+#define SPI_FLASH_SCK_PIN &pin_P0_19
+#define SPI_FLASH_CS_PIN &pin_P0_20
+#endif
+
+#define CIRCUITPY_AUTORELOAD_DELAY_MS 500
+
+#define CIRCUITPY_INTERNAL_NVM_SIZE (4096)
+
+#define BOARD_FLASH_SIZE (FLASH_SIZE - 0x4000 - CIRCUITPY_INTERNAL_NVM_SIZE)
+
+#define BOARD_HAS_CRYSTAL 1
+
+#define DEFAULT_I2C_BUS_SCL         (&pin_P0_16)
+#define DEFAULT_I2C_BUS_SDA         (&pin_P0_15)
+
+#define DEFAULT_SPI_BUS_SCK         (&pin_P0_07)
+#define DEFAULT_SPI_BUS_MOSI        (&pin_P1_08)
+#define DEFAULT_SPI_BUS_MISO        (&pin_P0_11)
+
+#define DEFAULT_UART_BUS_RX         (&pin_P0_24)
+#define DEFAULT_UART_BUS_TX         (&pin_P0_25)
diff --git a/ports/nrf/boards/metro_nrf52840_express/mpconfigboard.mk b/ports/nrf/boards/metro_nrf52840_express/mpconfigboard.mk
new file mode 100644
index 000000000..4c1c93c10
--- /dev/null
+++ b/ports/nrf/boards/metro_nrf52840_express/mpconfigboard.mk
@@ -0,0 +1,26 @@
+USB_VID = 0x239A
+USB_PID = 0x8040
+USB_PRODUCT = "Metro nRF52840 Express"
+USB_MANUFACTURER = "Adafruit Industries LLC"
+
+MCU_SERIES = m4
+MCU_VARIANT = nrf52
+MCU_SUB_VARIANT = nrf52840
+MCU_CHIP = nrf52840
+SD ?= s140
+SOFTDEV_VERSION ?= 6.1.0
+
+BOOT_SETTING_ADDR = 0xFF000
+
+ifeq ($(SD),)
+	LD_FILE = boards/nrf52840_1M_256k.ld
+else
+	LD_FILE = boards/adafruit_$(MCU_SUB_VARIANT)_$(SD_LOWER)_v$(firstword $(subst ., ,$(SOFTDEV_VERSION))).ld
+	CIRCUITPY_BLEIO = 1
+endif
+
+NRF_DEFINES += -DNRF52840_XXAA -DNRF52840
+
+QSPI_FLASH_FILESYSTEM = 1
+EXTERNAL_FLASH_DEVICE_COUNT = 1
+EXTERNAL_FLASH_DEVICES = "GD25Q16C"
diff --git a/ports/nrf/boards/metro_nrf52840_express/pins.c b/ports/nrf/boards/metro_nrf52840_express/pins.c
new file mode 100644
index 000000000..452e31202
--- /dev/null
+++ b/ports/nrf/boards/metro_nrf52840_express/pins.c
@@ -0,0 +1,56 @@
+#include "shared-bindings/board/__init__.h"
+
+STATIC const mp_rom_map_elem_t board_module_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_P0_04) },
+    { MP_ROM_QSTR(MP_QSTR_A1), MP_ROM_PTR(&pin_P0_05) },
+    { MP_ROM_QSTR(MP_QSTR_A2), MP_ROM_PTR(&pin_P0_28) },
+    { MP_ROM_QSTR(MP_QSTR_A3), MP_ROM_PTR(&pin_P0_30) },
+    { MP_ROM_QSTR(MP_QSTR_A4), MP_ROM_PTR(&pin_P0_02) },
+    { MP_ROM_QSTR(MP_QSTR_A5), MP_ROM_PTR(&pin_P0_03) },
+
+    { MP_ROM_QSTR(MP_QSTR_AREF), MP_ROM_PTR(&pin_P0_31) },
+
+    { MP_ROM_QSTR(MP_QSTR_SWITCH), MP_ROM_PTR(&pin_P1_02) },
+
+    { MP_ROM_QSTR(MP_QSTR_NFC1), MP_ROM_PTR(&pin_P0_09) },
+    { MP_ROM_QSTR(MP_QSTR_NFC2), MP_ROM_PTR(&pin_P0_10) },
+
+    { MP_ROM_QSTR(MP_QSTR_D0), MP_ROM_PTR(&pin_P0_24) },
+    { MP_ROM_QSTR(MP_QSTR_RX), MP_ROM_PTR(&pin_P0_24) },
+
+    { MP_ROM_QSTR(MP_QSTR_D1), MP_ROM_PTR(&pin_P0_25) },
+    { MP_ROM_QSTR(MP_QSTR_TX), MP_ROM_PTR(&pin_P0_25) },
+
+    { MP_ROM_QSTR(MP_QSTR_D2), MP_ROM_PTR(&pin_P1_10) },
+    { MP_ROM_QSTR(MP_QSTR_D3), MP_ROM_PTR(&pin_P1_04) },
+    { MP_ROM_QSTR(MP_QSTR_D4), MP_ROM_PTR(&pin_P1_11) },
+    { MP_ROM_QSTR(MP_QSTR_D5), MP_ROM_PTR(&pin_P1_12) },
+    { MP_ROM_QSTR(MP_QSTR_D6), MP_ROM_PTR(&pin_P1_14) },
+    { MP_ROM_QSTR(MP_QSTR_D7), MP_ROM_PTR(&pin_P0_26) },
+    { MP_ROM_QSTR(MP_QSTR_D8), MP_ROM_PTR(&pin_P0_27) },
+    { MP_ROM_QSTR(MP_QSTR_D9), MP_ROM_PTR(&pin_P0_12) },
+    { MP_ROM_QSTR(MP_QSTR_D10), MP_ROM_PTR(&pin_P0_06) },
+    { MP_ROM_QSTR(MP_QSTR_D11), MP_ROM_PTR(&pin_P0_08) },
+    { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_P1_09) },
+    { MP_ROM_QSTR(MP_QSTR_D13),MP_ROM_PTR(&pin_P0_14) },
+
+    { MP_ROM_QSTR(MP_QSTR_SDA), MP_ROM_PTR(&pin_P0_15) },
+    { MP_ROM_QSTR(MP_QSTR_SCL), MP_ROM_PTR(&pin_P0_16) },
+
+    { MP_ROM_QSTR(MP_QSTR_NEOPIXEL),MP_ROM_PTR(&pin_P0_13) },
+
+    { MP_ROM_QSTR(MP_QSTR_SCK),  MP_ROM_PTR(&pin_P0_07) },
+    { MP_ROM_QSTR(MP_QSTR_MOSI), MP_ROM_PTR(&pin_P1_08) },
+    { MP_ROM_QSTR(MP_QSTR_MISO), MP_ROM_PTR(&pin_P0_11) },
+
+    { MP_ROM_QSTR(MP_QSTR_L), MP_ROM_PTR(&pin_P1_13) },
+    { MP_ROM_QSTR(MP_QSTR_RED_LED), MP_ROM_PTR(&pin_P1_13) },
+
+    { MP_ROM_QSTR(MP_QSTR_BLUE_LED), MP_ROM_PTR(&pin_P1_15) },
+
+    { MP_ROM_QSTR(MP_QSTR_UART), MP_ROM_PTR(&board_uart_obj) },
+    { MP_ROM_QSTR(MP_QSTR_SPI), MP_ROM_PTR(&board_spi_obj) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
+};
+
+MP_DEFINE_CONST_DICT(board_module_globals, board_module_globals_table);
diff --git a/ports/nrf/boards/particle_argon/mpconfigboard.h b/ports/nrf/boards/particle_argon/mpconfigboard.h
index 0ee785c31..a4ecb2bb4 100644
--- a/ports/nrf/boards/particle_argon/mpconfigboard.h
+++ b/ports/nrf/boards/particle_argon/mpconfigboard.h
@@ -27,8 +27,6 @@
 
 #include "nrfx/hal/nrf_gpio.h"
 
-#define FEATHER52840
-
 #define MICROPY_HW_BOARD_NAME       "Particle Argon"
 #define MICROPY_HW_MCU_NAME         "nRF52840"
 #define MICROPY_PY_SYS_PLATFORM     "Particle Argon"
diff --git a/ports/nrf/boards/particle_boron/mpconfigboard.h b/ports/nrf/boards/particle_boron/mpconfigboard.h
index b814fc694..5e817311f 100644
--- a/ports/nrf/boards/particle_boron/mpconfigboard.h
+++ b/ports/nrf/boards/particle_boron/mpconfigboard.h
@@ -27,8 +27,6 @@
 
 #include "nrfx/hal/nrf_gpio.h"
 
-#define FEATHER52840
-
 #define MICROPY_HW_BOARD_NAME       "Particle Boron"
 #define MICROPY_HW_MCU_NAME         "nRF52840"
 #define MICROPY_PY_SYS_PLATFORM     "Particle Boron"
diff --git a/ports/nrf/boards/particle_xenon/mpconfigboard.h b/ports/nrf/boards/particle_xenon/mpconfigboard.h
index c8da66736..6c8cc7cef 100644
--- a/ports/nrf/boards/particle_xenon/mpconfigboard.h
+++ b/ports/nrf/boards/particle_xenon/mpconfigboard.h
@@ -27,8 +27,6 @@
 
 #include "nrfx/hal/nrf_gpio.h"
 
-#define FEATHER52840
-
 #define MICROPY_HW_BOARD_NAME       "Particle Xenon"
 #define MICROPY_HW_MCU_NAME         "nRF52840"
 #define MICROPY_PY_SYS_PLATFORM     "Particle Xenon"
diff --git a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c
new file mode 100644
index 000000000..0321b751c
--- /dev/null
+++ b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c
@@ -0,0 +1,316 @@
+/*
+ * 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 <stdint.h>
+#include <string.h>
+
+#include "extmod/vfs_fat.h"
+#include "py/gc.h"
+#include "py/mperrno.h"
+#include "py/runtime.h"
+#include "common-hal/audiopwmio/PWMAudioOut.h"
+#include "common-hal/pulseio/PWMOut.h"
+#include "shared-bindings/audiopwmio/PWMAudioOut.h"
+#include "shared-bindings/microcontroller/__init__.h"
+#include "shared-bindings/microcontroller/Pin.h"
+#include "supervisor/shared/translate.h"
+
+// TODO: This should be the same size as PWMOut.c:pwms[], but there's no trivial way to accomplish that
+STATIC audiopwmio_pwmaudioout_obj_t* active_audio[4];
+
+#define F_TARGET (62500)
+#define F_PWM (16000000)
+// return the REFRESH value, store the TOP value in an out-parameter
+// Tested for key values (worst relative error = 0.224% = 3.84 cents)
+//  8000: top = 250 refresh = 7 [ 8000.0]
+// 22050: top = 242 refresh = 2 [22038.5]
+// 24000: top = 222 refresh = 2 [24024.0]
+// 44100: top = 181 refresh = 1 [44198.8]
+// 48000: top = 167 refresh = 1 [47904.1]
+STATIC uint32_t calculate_pwm_parameters(uint32_t sample_rate, uint32_t *top_out) {
+    // the desired frequency is the closest integer multiple of sample_rate not less than F_TARGET
+    uint32_t desired_frequency = (F_TARGET + sample_rate - 1) / sample_rate * sample_rate;
+    // The top value is the PWM frequency divided by the desired frequency (round to nearest)
+    uint32_t top = (F_PWM + desired_frequency/2) / desired_frequency;
+    // The actual frequency is the PWM frequency divided by the top value (round to nearest)
+    uint32_t actual_frequency = (F_PWM + top/2) / top;
+    // The multiplier is the actual frequency divided by the sample rate (round to nearest)
+    uint32_t multiplier = (actual_frequency + sample_rate/2) / sample_rate;
+    *top_out = top;
+    return multiplier - 1;
+}
+
+STATIC void activate_audiopwmout_obj(audiopwmio_pwmaudioout_obj_t *self) {
+    for(size_t i=0; i < MP_ARRAY_SIZE(active_audio); i++) {
+        if(!active_audio[i]) {
+            active_audio[i] = self;
+            break;
+        }
+    }
+}
+STATIC void deactivate_audiopwmout_obj(audiopwmio_pwmaudioout_obj_t *self) {
+    for(size_t i=0; i < MP_ARRAY_SIZE(active_audio); i++) {
+        if(active_audio[i] == self)
+            active_audio[i] = NULL;
+    }
+}
+
+void audiopwmout_reset() {
+    for(size_t i=0; i < MP_ARRAY_SIZE(active_audio); i++)
+        active_audio[i] = NULL;
+}
+
+STATIC void fill_buffers(audiopwmio_pwmaudioout_obj_t *self, int buf) {
+    self->pwm->EVENTS_SEQSTARTED[1-buf] = 0;
+    uint16_t *dev_buffer = self->buffers[buf];
+    uint8_t *buffer;
+    uint32_t buffer_length;
+    audioio_get_buffer_result_t get_buffer_result =
+        audiosample_get_buffer(self->sample, false, 0,
+                               &buffer, &buffer_length);
+    if (get_buffer_result == GET_BUFFER_ERROR) {
+        common_hal_audiopwmio_pwmaudioout_stop(self);
+        return;
+    }
+    uint32_t num_samples = buffer_length / self->bytes_per_sample / self->spacing;
+
+    if(self->bytes_per_sample == 1) {
+        uint8_t offset = self->signed_to_unsigned ? 0x80 : 0;
+        uint16_t scale = self->scale;
+        for(uint32_t i=0; i<buffer_length/self->spacing; i++) {
+            uint8_t rawval = (*buffer++ + offset);
+            uint16_t val = (uint16_t)(((uint32_t)rawval * (uint32_t)scale) >> 8);
+            *dev_buffer++ = val;
+            if(self->spacing == 1)
+                *dev_buffer++ = val;
+        }
+    } else {
+        uint16_t offset = self->signed_to_unsigned ? 0x8000 : 0;
+        uint16_t scale = self->scale;
+        uint16_t *buffer16 = (uint16_t*)buffer;
+        for(uint32_t i=0; i<buffer_length/2/self->spacing; i++) {
+            uint16_t rawval = (*buffer16++ + offset);
+            uint16_t val = (uint16_t)((rawval * (uint32_t)scale) >> 16);
+            *dev_buffer++ = val;
+            if(self->spacing == 1)
+                *dev_buffer++ = val;
+        }
+    }
+    self->pwm->SEQ[buf].PTR = (intptr_t)self->buffers[buf];
+    self->pwm->SEQ[buf].CNT = num_samples*2;
+
+    if (self->loop && get_buffer_result == GET_BUFFER_DONE) {
+        audiosample_reset_buffer(self->sample, false, 0);
+    } else if(get_buffer_result == GET_BUFFER_DONE) {
+        self->pwm->SHORTS = NRF_PWM_SHORT_SEQEND0_STOP_MASK | NRF_PWM_SHORT_SEQEND1_STOP_MASK;
+        self->stopping = true;
+    }
+}
+
+STATIC void audiopwmout_background_obj(audiopwmio_pwmaudioout_obj_t *self) {
+    if(!common_hal_audiopwmio_pwmaudioout_get_playing(self))
+        return;
+    if(self->stopping) {
+        bool stopped =
+            (self->pwm->EVENTS_SEQEND[0] || !self->pwm->EVENTS_SEQSTARTED[0]) &&
+            (self->pwm->EVENTS_SEQEND[1] || !self->pwm->EVENTS_SEQSTARTED[1]);
+        if(stopped)
+            self->pwm->TASKS_STOP = 1;
+    } else if(!self->paused && !self->single_buffer) {
+        if(self->pwm->EVENTS_SEQSTARTED[0]) fill_buffers(self, 1);
+        if(self->pwm->EVENTS_SEQSTARTED[1]) fill_buffers(self, 0);
+    }
+}
+
+void audiopwmout_background() {
+    for(size_t i=0; i < MP_ARRAY_SIZE(active_audio); i++) {
+        if(!active_audio[i]) continue;
+        audiopwmout_background_obj(active_audio[i]);
+    }
+}
+
+void common_hal_audiopwmio_pwmaudioout_construct(audiopwmio_pwmaudioout_obj_t* self,
+        const mcu_pin_obj_t* left_channel, const mcu_pin_obj_t* right_channel, uint16_t quiescent_value) {
+    assert_pin_free(left_channel);
+    assert_pin_free(right_channel);
+    self->pwm = pwmout_allocate(256, PWM_PRESCALER_PRESCALER_DIV_1, true, NULL, NULL);
+    if(!self->pwm) {
+        mp_raise_RuntimeError(translate("All timers in use"));
+    }
+
+    self->pwm->PRESCALER = PWM_PRESCALER_PRESCALER_DIV_1;
+    // two uint16_t values per sample when Grouped
+    // n.b. SEQ[#].CNT "counts" are 2 per sample (left and right channels)
+    self->pwm->DECODER = PWM_DECODER_LOAD_Grouped;
+
+    // we use channels 0 and 2 because these are GROUPED; it lets us save half
+    // the space for sample data (no additional optimization is possible for
+    // single channel)
+    self->pwm->PSEL.OUT[0] = self->left_channel_number = left_channel->number;
+    claim_pin(left_channel);
+
+    if(right_channel)
+    {
+        self->pwm->PSEL.OUT[2] = self->right_channel_number = right_channel->number;
+        claim_pin(right_channel);
+    }
+
+    self->quiescent_value = quiescent_value >> 8;
+
+    self->pwm->ENABLE = 1;
+    // TODO: Ramp from 0 to quiescent value
+}
+
+bool common_hal_audiopwmio_pwmaudioout_deinited(audiopwmio_pwmaudioout_obj_t* self) {
+    return !self->pwm;
+}
+
+void common_hal_audiopwmio_pwmaudioout_deinit(audiopwmio_pwmaudioout_obj_t* self) {
+    if (common_hal_audiopwmio_pwmaudioout_deinited(self)) {
+        return;
+    }
+    // TODO: ramp the pwm down from quiescent value to 0
+    self->pwm->ENABLE = 0;
+
+    if(self->left_channel_number)
+        reset_pin_number(self->left_channel_number);
+    if(self->right_channel_number)
+        reset_pin_number(self->right_channel_number);
+
+    pwmout_free_channel(self->pwm, 0);
+    pwmout_free_channel(self->pwm, 2);
+
+    self->pwm = NULL;
+
+    m_free(self->buffers[0]);
+    self->buffers[0] = NULL;
+
+    m_free(self->buffers[1]);
+    self->buffers[1] = NULL;
+}
+
+void common_hal_audiopwmio_pwmaudioout_play(audiopwmio_pwmaudioout_obj_t* self, mp_obj_t sample, bool loop) {
+    if (common_hal_audiopwmio_pwmaudioout_get_playing(self)) {
+        common_hal_audiopwmio_pwmaudioout_stop(self);
+    }
+    self->sample = sample;
+    self->loop = loop;
+
+    uint32_t sample_rate = audiosample_sample_rate(sample);
+    uint32_t max_sample_rate = 62500;
+    if (sample_rate > max_sample_rate) {
+        mp_raise_ValueError_varg(translate("Sample rate too high. It must be less than %d"), max_sample_rate);
+    }
+    self->bytes_per_sample = audiosample_bits_per_sample(sample) / 8;
+
+    uint32_t max_buffer_length;
+    audiosample_get_buffer_structure(sample, /* single channel */ false,
+        &self->single_buffer, &self->signed_to_unsigned, &max_buffer_length,
+        &self->spacing);
+    if(max_buffer_length > UINT16_MAX) {
+        mp_raise_ValueError_varg(translate("Buffer length %d too big. It must be less than %d"), max_buffer_length, UINT16_MAX);
+    }
+    self->buffer_length = (uint16_t)max_buffer_length;
+    self->buffers[0] = m_malloc(self->buffer_length * 2 * sizeof(uint16_t), false);
+    if(!self->single_buffer)
+        self->buffers[1] = m_malloc(self->buffer_length * 2 * sizeof(uint16_t), false);
+
+
+    uint32_t top;
+    self->pwm->SEQ[0].REFRESH = self->pwm->SEQ[1].REFRESH = calculate_pwm_parameters(sample_rate, &top);
+    self->scale = top-1;
+    self->pwm->COUNTERTOP = top;
+
+    self->pwm->LOOP = 1;
+    audiosample_reset_buffer(self->sample, false, 0);
+    activate_audiopwmout_obj(self);
+    fill_buffers(self, 0);
+    self->pwm->SEQ[1].PTR = self->pwm->SEQ[0].PTR;
+    self->pwm->SEQ[1].CNT = self->pwm->SEQ[0].CNT;
+    self->pwm->EVENTS_SEQSTARTED[0] = 0;
+    self->pwm->EVENTS_SEQSTARTED[1] = 0;
+    self->pwm->EVENTS_STOPPED = 0;
+    self->pwm->SHORTS = NRF_PWM_SHORT_LOOPSDONE_SEQSTART0_MASK;
+    self->pwm->TASKS_SEQSTART[0] = 1;
+    self->playing = true;
+    self->stopping = false;
+    self->paused = false;
+}
+
+void common_hal_audiopwmio_pwmaudioout_stop(audiopwmio_pwmaudioout_obj_t* self) {
+    deactivate_audiopwmout_obj(self);
+    self->pwm->TASKS_STOP = 1;
+    self->stopping = false;
+    self->paused = false;
+
+    m_free(self->buffers[0]);
+    self->buffers[0] = NULL;
+
+    m_free(self->buffers[1]);
+    self->buffers[1] = NULL;
+}
+
+bool common_hal_audiopwmio_pwmaudioout_get_playing(audiopwmio_pwmaudioout_obj_t* self) {
+    if(!self->paused && self->pwm->EVENTS_STOPPED) {
+        self->playing = false;
+        self->pwm->EVENTS_STOPPED = 0;
+    }
+    return self->playing;
+}
+
+/* pause/resume present difficulties for the NRF PWM audio module.
+ *
+ * A PWM sequence can be stopped in its tracks by sending a TASKS_STOP event,
+ * but there's no way to pick up the sequence where it was stopped; you could
+ * start at the start of one of the two sequences, but especially for "single buffer"
+ * sample, this seems undesirable.
+ *
+ * Or, you can stop at the end of a sequence so that you don't duplicate anything
+ * when restarting, but again this is unsatisfactory for a "single buffer" sample.
+ *
+ * For now, I've taken the coward's way and left these methods unimplemented.
+ * Perhaps the way forward is to divide even "single buffer" samples into tasks of
+ * only a few ms long, so that they can be stopped/restarted quickly enough that it
+ * feels instant. (This also saves on memory, for long in-memory "single buffer"
+ * samples, since we have to locally take a resampled copy!)
+ */
+void common_hal_audiopwmio_pwmaudioout_pause(audiopwmio_pwmaudioout_obj_t* self) {
+    self->paused = true;
+    self->pwm->SHORTS = NRF_PWM_SHORT_SEQEND1_STOP_MASK;
+}
+
+void common_hal_audiopwmio_pwmaudioout_resume(audiopwmio_pwmaudioout_obj_t* self) {
+    self->paused = false;
+    self->pwm->SHORTS = NRF_PWM_SHORT_LOOPSDONE_SEQSTART0_MASK;
+    if (self->pwm->EVENTS_STOPPED) {
+        self->pwm->EVENTS_STOPPED = 0;
+        self->pwm->TASKS_SEQSTART[0] = 1;
+    }
+}
+
+bool common_hal_audiopwmio_pwmaudioout_get_paused(audiopwmio_pwmaudioout_obj_t* self) {
+    return self->paused;
+}
diff --git a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h
new file mode 100644
index 000000000..8deff5d34
--- /dev/null
+++ b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h
@@ -0,0 +1,59 @@
+/*
+ * 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_AUDIOPWM_AUDIOOUT_H
+#define MICROPY_INCLUDED_NRF_COMMON_HAL_AUDIOPWM_AUDIOOUT_H
+
+#include "common-hal/microcontroller/Pin.h"
+
+typedef struct {
+    mp_obj_base_t base;
+    mp_obj_t *sample;
+    NRF_PWM_Type *pwm;
+    uint16_t *buffers[2];
+
+    uint16_t buffer_length;
+    uint16_t quiescent_value;
+    uint16_t scale;
+
+    uint8_t left_channel_number;
+    uint8_t right_channel_number;
+    uint8_t spacing;
+    uint8_t bytes_per_sample;
+
+    bool playing;
+    bool stopping;
+    bool paused;
+    bool loop;
+    bool signed_to_unsigned;
+    bool single_buffer;
+} audiopwmio_pwmaudioout_obj_t;
+
+void audiopwmout_reset(void);
+
+void audiopwmout_background(void);
+
+#endif
diff --git a/ports/nrf/common-hal/audiopwmio/__init__.c b/ports/nrf/common-hal/audiopwmio/__init__.c
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/ports/nrf/common-hal/audiopwmio/__init__.c
diff --git a/ports/nrf/common-hal/pulseio/PWMOut.c b/ports/nrf/common-hal/pulseio/PWMOut.c
index 5233c9adc..b827470d3 100644
--- a/ports/nrf/common-hal/pulseio/PWMOut.c
+++ b/ports/nrf/common-hal/pulseio/PWMOut.c
@@ -57,6 +57,12 @@ STATIC uint16_t pwm_seq[MP_ARRAY_SIZE(pwms)][CHANNELS_PER_PWM];
 
 static uint8_t never_reset_pwm[MP_ARRAY_SIZE(pwms)];
 
+STATIC int pwm_idx(NRF_PWM_Type *pwm) {
+    for(size_t i=0; i < MP_ARRAY_SIZE(pwms); i++)
+        if(pwms[i] == pwm) return i;
+    return -1;
+}
+
 void common_hal_pulseio_pwmout_never_reset(pulseio_pwmout_obj_t *self) {
     for(size_t i=0; i < MP_ARRAY_SIZE(pwms); i++) {
         NRF_PWM_Type* pwm = pwms[i];
@@ -133,29 +139,11 @@ bool convert_frequency(uint32_t frequency, uint16_t *countertop, nrf_pwm_clk_t *
     return false;
 }
 
-pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
-                                                    const mcu_pin_obj_t* pin,
-                                                    uint16_t duty,
-                                                    uint32_t frequency,
-                                                    bool variable_frequency) {
-
-    // We don't use the nrfx driver here because we want to dynamically allocate channels
-    // as needed in an already-enabled PWM.
-
-    uint16_t countertop;
-    nrf_pwm_clk_t base_clock;
-    if (frequency == 0 || !convert_frequency(frequency, &countertop, &base_clock)) {
-        return PWMOUT_INVALID_FREQUENCY;
-    }
-
-    self->pwm = NULL;
-    self->channel = CHANNELS_PER_PWM;    // out-of-range value.
-    bool pwm_already_in_use;
-    NRF_PWM_Type* pwm;
-    size_t pwm_index = 0;
-    for (; pwm_index < MP_ARRAY_SIZE(pwms); pwm_index++) {
-        pwm = pwms[pwm_index];
-        pwm_already_in_use = pwm->ENABLE & SPIM_ENABLE_ENABLE_Msk;
+NRF_PWM_Type *pwmout_allocate(uint16_t countertop, nrf_pwm_clk_t base_clock,
+        bool variable_frequency, int8_t *channel_out, bool *pwm_already_in_use_out) {
+    for (size_t pwm_index = 0; pwm_index < MP_ARRAY_SIZE(pwms); pwm_index++) {
+        NRF_PWM_Type *pwm = pwms[pwm_index];
+        bool pwm_already_in_use = pwm->ENABLE & SPIM_ENABLE_ENABLE_Msk;
         if (pwm_already_in_use) {
             if (variable_frequency) {
                 // Variable frequency requires exclusive use of a PWM, so try the next one.
@@ -168,28 +156,65 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
                 for (size_t chan = 0; chan < CHANNELS_PER_PWM; chan++) {
                     if (pwm->PSEL.OUT[chan] == 0xFFFFFFFF) {
                         // Channel is free.
-                        self->pwm = pwm;
-                        self->channel = chan;
-                        break;
+                        if(channel_out)
+                            *channel_out = chan;
+                        if(pwm_already_in_use_out)
+                            *pwm_already_in_use_out = pwm_already_in_use;
+                        return pwm;
                     }
                 }
-                // Did we find a channel? If not, loop and check the next pwm.
-                if (self->pwm != NULL) {
-                    break;
-                }
             }
         } else {
             // PWM not yet in use, so we can start to use it. Use channel 0.
-            self->pwm = pwm;
-            self->channel = 0;
-            break;
+            if(channel_out)
+                *channel_out = 0;
+            if(pwm_already_in_use_out)
+                *pwm_already_in_use_out = pwm_already_in_use;
+            return pwm;
         }
     }
+    return NULL;
+}
+
+void pwmout_free_channel(NRF_PWM_Type *pwm, int8_t channel) {
+    // Disconnect pin from channel.
+    pwm->PSEL.OUT[channel] = 0xFFFFFFFF;
+
+    for(int i=0; i < CHANNELS_PER_PWM; i++) {
+        if (pwm->PSEL.OUT[i] != 0xFFFFFFFF) {
+            // Some channel is still being used, so don't disable.
+            return;
+        }
+    }
+
+    nrf_pwm_disable(pwm);
+}
+
+pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
+                                                    const mcu_pin_obj_t* pin,
+                                                    uint16_t duty,
+                                                    uint32_t frequency,
+                                                    bool variable_frequency) {
+
+    // We don't use the nrfx driver here because we want to dynamically allocate channels
+    // as needed in an already-enabled PWM.
+
+    uint16_t countertop;
+    nrf_pwm_clk_t base_clock;
+    if (frequency == 0 || !convert_frequency(frequency, &countertop, &base_clock)) {
+        return PWMOUT_INVALID_FREQUENCY;
+    }
+
+    int8_t channel;
+    bool pwm_already_in_use;
+    self->pwm = pwmout_allocate(countertop, base_clock, variable_frequency,
+        &channel, &pwm_already_in_use);
 
     if (self->pwm == NULL) {
         return PWMOUT_ALL_TIMERS_IN_USE;
     }
 
+    self->channel = channel;
     self->pin_number = pin->number;
     claim_pin(pin);
 
@@ -200,17 +225,17 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
     nrf_gpio_cfg_output(self->pin_number);
 
     // disable before mapping pin channel
-    nrf_pwm_disable(pwm);
+    nrf_pwm_disable(self->pwm);
 
     if (!pwm_already_in_use) {
-        reset_single_pwmout(pwm_index);
-        nrf_pwm_configure(pwm, base_clock, NRF_PWM_MODE_UP, countertop);
+        reset_single_pwmout(pwm_idx(self->pwm));
+        nrf_pwm_configure(self->pwm, base_clock, NRF_PWM_MODE_UP, countertop);
     }
 
     // Connect channel to pin, without disturbing other channels.
-    pwm->PSEL.OUT[self->channel] = pin->number;
+    self->pwm->PSEL.OUT[self->channel] = pin->number;
 
-    nrf_pwm_enable(pwm);
+    nrf_pwm_enable(self->pwm);
 
     common_hal_pulseio_pwmout_set_duty_cycle(self, duty);
     return PWMOUT_OK;
@@ -230,17 +255,7 @@ void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t* self) {
     NRF_PWM_Type* pwm = self->pwm;
     self->pwm = NULL;
 
-    // Disconnect pin from channel.
-    pwm->PSEL.OUT[self->channel] = 0xFFFFFFFF;
-
-    for(int i=0; i < CHANNELS_PER_PWM; i++) {
-        if (self->pwm->PSEL.OUT[i] != 0xFFFFFFFF) {
-            // Some channel is still being used, so don't disable.
-            return;
-        }
-    }
-
-    nrf_pwm_disable(pwm);
+    pwmout_free_channel(pwm, self->channel);
 }
 
 void common_hal_pulseio_pwmout_set_duty_cycle(pulseio_pwmout_obj_t* self, uint16_t duty_cycle) {
diff --git a/ports/nrf/common-hal/pulseio/PWMOut.h b/ports/nrf/common-hal/pulseio/PWMOut.h
index a4e58dc1a..b6798cb68 100644
--- a/ports/nrf/common-hal/pulseio/PWMOut.h
+++ b/ports/nrf/common-hal/pulseio/PWMOut.h
@@ -41,5 +41,8 @@ typedef struct {
 } pulseio_pwmout_obj_t;
 
 void pwmout_reset(void);
+NRF_PWM_Type *pwmout_allocate(uint16_t countertop, nrf_pwm_clk_t base_clock,
+    bool variable_frequency, int8_t *channel_out, bool *pwm_already_in_use_out);
+void pwmout_free_channel(NRF_PWM_Type *pwm, int8_t channel);
 
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_PULSEIO_PWMOUT_H
diff --git a/ports/nrf/mpconfigport.mk b/ports/nrf/mpconfigport.mk
index 83166708a..57879bbaa 100644
--- a/ports/nrf/mpconfigport.mk
+++ b/ports/nrf/mpconfigport.mk
@@ -10,8 +10,10 @@ USB_SERIAL_NUMBER_LENGTH = 16
 # All nRF ports have longints.
 LONGINT_IMPL = MPZ
 
-# No DAC, so no regular audio.
+# Audio via PWM
+CIRCUITPY_AUDIOCORE = 1
 CIRCUITPY_AUDIOIO = 0
+CIRCUITPY_AUDIOPWMIO = 1
 
 # No I2S yet.
 CIRCUITPY_AUDIOBUSIO = 0
diff --git a/ports/nrf/supervisor/port.c b/ports/nrf/supervisor/port.c
index 8fbf75498..03f787624 100644
--- a/ports/nrf/supervisor/port.c
+++ b/ports/nrf/supervisor/port.c
@@ -50,6 +50,10 @@
 
 #include "shared-bindings/rtc/__init__.h"
 
+#ifdef CIRCUITPY_AUDIOPWMIO
+#include "common-hal/audiopwmio/PWMAudioOut.h"
+#endif
+
 static void power_warning_handler(void) {
     reset_into_safe_mode(BROWNOUT);
 }
@@ -94,6 +98,10 @@ void reset_port(void) {
     spi_reset();
     uart_reset();
 
+#ifdef CIRCUITPY_AUDIOPWMIO
+    audiopwmout_reset();
+#endif
+
 #if CIRCUITPY_PULSEIO
     pwmout_reset();
     pulseout_reset();