diff --git a/locale/circuitpython.pot b/locale/circuitpython.pot
index 7b0020aa18..3bec8b622b 100644
--- a/locale/circuitpython.pot
+++ b/locale/circuitpython.pot
@@ -1535,6 +1535,11 @@ msgstr ""
 msgid "Microphone startup delay must be in range 0.0 to 1.0"
 msgstr ""
 
+#: ports/raspberrypi/bindings/rp2pio/StateMachine.c
+#: ports/raspberrypi/common-hal/rp2pio/StateMachine.c
+msgid "Mismatched data size"
+msgstr ""
+
 #: ports/mimxrt10xx/common-hal/busio/SPI.c ports/stm/common-hal/busio/SPI.c
 msgid "Missing MISO or MOSI Pin"
 msgstr ""
diff --git a/ports/raspberrypi/audio_dma.c b/ports/raspberrypi/audio_dma.c
index b7e5a0db44..7fef1a52e0 100644
--- a/ports/raspberrypi/audio_dma.c
+++ b/ports/raspberrypi/audio_dma.c
@@ -29,6 +29,7 @@
 #include "shared-bindings/audiocore/RawSample.h"
 #include "shared-bindings/audiocore/WaveFile.h"
 #include "shared-bindings/microcontroller/__init__.h"
+#include "bindings/rp2pio/StateMachine.h"
 #include "supervisor/background_callback.h"
 
 #include "py/mpstate.h"
@@ -324,7 +325,9 @@ void audio_dma_stop(audio_dma_t *dma) {
         channel_mask |= 1 << dma->channel[1];
     }
     dma_hw->inte0 &= ~channel_mask;
-    irq_set_mask_enabled(1 << DMA_IRQ_0, false);
+    if (!dma_hw->inte0) {
+        irq_set_mask_enabled(1 << DMA_IRQ_0, false);
+    }
 
     // Run any remaining audio tasks because we remove ourselves from
     // playing_audio.
@@ -442,12 +445,23 @@ STATIC void dma_callback_fun(void *arg) {
 void isr_dma_0(void) {
     for (size_t i = 0; i < NUM_DMA_CHANNELS; i++) {
         uint32_t mask = 1 << i;
-        if ((dma_hw->intr & mask) != 0 && MP_STATE_PORT(playing_audio)[i] != NULL) {
+        if ((dma_hw->intr & mask) == 0) {
+            continue;
+        }
+        // acknowledge interrupt early. Doing so late means that you could lose an
+        // interrupt if the buffer is very small and the DMA operation
+        // completed by the time callback_add() / dma_complete() returned. This
+        // affected PIO continuous write more than audio.
+        dma_hw->ints0 = mask;
+        if (MP_STATE_PORT(playing_audio)[i] != NULL) {
             audio_dma_t *dma = MP_STATE_PORT(playing_audio)[i];
             // Record all channels whose DMA has completed; they need loading.
             dma->channels_to_load_mask |= mask;
             background_callback_add(&dma->callback, dma_callback_fun, (void *)dma);
-            dma_hw->ints0 = mask;
+        }
+        if (MP_STATE_PORT(background_pio)[i] != NULL) {
+            rp2pio_statemachine_obj_t *pio = MP_STATE_PORT(background_pio)[i];
+            rp2pio_statemachine_dma_complete(pio, i);
         }
     }
 }
diff --git a/ports/raspberrypi/bindings/rp2pio/StateMachine.c b/ports/raspberrypi/bindings/rp2pio/StateMachine.c
index 98213be265..722b1f7c7f 100644
--- a/ports/raspberrypi/bindings/rp2pio/StateMachine.c
+++ b/ports/raspberrypi/bindings/rp2pio/StateMachine.c
@@ -426,6 +426,141 @@ STATIC mp_obj_t rp2pio_statemachine_write(size_t n_args, const mp_obj_t *pos_arg
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(rp2pio_statemachine_write_obj, 2, rp2pio_statemachine_write);
 
+//|     def background_write(self, once: Optional[ReadableBuffer]=None, *, loop: Optional[ReadableBuffer]=None) -> None:
+//|         """Write data to the TX fifo in the background, with optional looping.
+//|
+//|         First, if any previous ``once`` or ``loop`` buffer has not been started, this function blocks until they have.
+//|         This means that any ``once`` or ``loop`` buffer will be written at least once.
+//|         Then the ``once`` and/or ``loop`` buffers are queued. and the function returns.
+//|         The ``once`` buffer (if specified) will be written just once.
+//|         Finally, the ``loop`` buffer (if specified) will continue being looped indefinitely.
+//|
+//|         Writes to the FIFO will match the input buffer's element size. For example, bytearray elements
+//|         will perform 8 bit writes to the PIO FIFO. The RP2040's memory bus will duplicate the value into
+//|         the other byte positions. So, pulling more data in the PIO assembly will read the duplicated values.
+//|
+//|         To perform 16 or 32 bits writes into the FIFO use an `array.array` with a type code of the desired
+//|         size, or use `memoryview.cast` to change the interpretation of an
+//|         existing buffer.  To send just part of a larger buffer, slice a `memoryview`
+//|         of it.
+//|
+//|         If a buffer is modified while it is being written out, the updated
+//|         values will be used. However, because of interactions between CPU
+//|         writes, DMA and the PIO FIFO are complex, it is difficult to predict
+//|         the result of modifying multiple values. Instead, alternate between
+//|         a pair of buffers.
+//|
+//|         Having both a ``once`` and a ``loop`` parameter is to support a special case in PWM generation
+//|         where a change in duty cycle requires a special transitional buffer to be used exactly once. Most
+//|         use cases will probably only use one of ``once`` or ``loop``.
+//|
+//|         :param ~Optional[circuitpython_typing.ReadableBuffer] once: Data to be written once
+//|         :param ~Optional[circuitpython_typing.ReadableBuffer] loop: Data to be written repeatedly
+//|         """
+//|         ...
+//|
+
+STATIC void fill_buf_info(sm_buf_info *info, mp_obj_t obj, size_t *stride_in_bytes) {
+    if (obj != mp_const_none) {
+        info->obj = obj;
+        mp_get_buffer_raise(obj, &info->info, MP_BUFFER_READ);
+        size_t stride = mp_binary_get_size('@', info->info.typecode, NULL);
+        if (stride > 4) {
+            mp_raise_ValueError(translate("Buffer elements must be 4 bytes long or less"));
+        }
+        if (*stride_in_bytes && stride != *stride_in_bytes) {
+            mp_raise_ValueError(translate("Mismatched data size"));
+        }
+        *stride_in_bytes = stride;
+    } else {
+        memset(info, 0, sizeof(*info));
+    }
+}
+
+STATIC mp_obj_t rp2pio_statemachine_background_write(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_once, ARG_loop };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_once,     MP_ARG_OBJ, {.u_obj = mp_const_none} },
+        { MP_QSTR_loop,     MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none} },
+    };
+    rp2pio_statemachine_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
+    check_for_deinit(self);
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    sm_buf_info once_info;
+    sm_buf_info loop_info;
+    size_t stride_in_bytes = 0;
+    fill_buf_info(&once_info, args[ARG_once].u_obj, &stride_in_bytes);
+    fill_buf_info(&loop_info, args[ARG_loop].u_obj, &stride_in_bytes);
+    if (!stride_in_bytes) {
+        return mp_const_none;
+    }
+
+    bool ok = common_hal_rp2pio_statemachine_background_write(self, &once_info, &loop_info, stride_in_bytes);
+
+    if (mp_hal_is_interrupted()) {
+        return mp_const_none;
+    }
+    if (!ok) {
+        mp_raise_OSError(MP_EIO);
+    }
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(rp2pio_statemachine_background_write_obj, 1, rp2pio_statemachine_background_write);
+
+//|     def stop_background_write(self) -> None:
+//|         """Immediately stop a background write, if one is in progress.  Items already in the TX FIFO are not affected."""
+//|
+STATIC mp_obj_t rp2pio_statemachine_obj_stop_background_write(mp_obj_t self_in) {
+    rp2pio_statemachine_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    bool ok = common_hal_rp2pio_statemachine_stop_background_write(self);
+    if (mp_hal_is_interrupted()) {
+        return mp_const_none;
+    }
+    if (!ok) {
+        mp_raise_OSError(MP_EIO);
+    }
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_1(rp2pio_statemachine_stop_background_write_obj, rp2pio_statemachine_obj_stop_background_write);
+
+//|     @property
+//|     def writing(self) -> bool:
+//|         """Returns True if a background write is in progress"""
+//|
+STATIC mp_obj_t rp2pio_statemachine_obj_get_writing(mp_obj_t self_in) {
+    rp2pio_statemachine_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return mp_obj_new_bool(common_hal_rp2pio_statemachine_get_writing(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(rp2pio_statemachine_get_writing_obj, rp2pio_statemachine_obj_get_writing);
+
+const mp_obj_property_t rp2pio_statemachine_writing_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&rp2pio_statemachine_get_writing_obj,
+              MP_ROM_NONE,
+              MP_ROM_NONE},
+};
+
+
+//|     @property
+//|     def pending(self) -> int:
+//|         """Returns the number of pending buffers for background writing.
+//|
+//|         If the number is 0, then a `StateMachine.background_write` call will not block."""
+//|
+STATIC mp_obj_t rp2pio_statemachine_obj_get_pending(mp_obj_t self_in) {
+    rp2pio_statemachine_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return mp_obj_new_int(common_hal_rp2pio_statemachine_get_pending(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(rp2pio_statemachine_get_pending_obj, rp2pio_statemachine_obj_get_pending);
+
+const mp_obj_property_t rp2pio_statemachine_pending_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&rp2pio_statemachine_get_pending_obj,
+              MP_ROM_NONE,
+              MP_ROM_NONE},
+};
 
 //|     def readinto(self, buffer: WriteableBuffer, *, start: int = 0, end: Optional[int] = None) -> None:
 //|         """Read into ``buffer``. If the number of bytes to read is 0, nothing happens. The buffer
@@ -646,6 +781,10 @@ STATIC const mp_rom_map_elem_t rp2pio_statemachine_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&rp2pio_statemachine_readinto_obj) },
     { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&rp2pio_statemachine_write_obj) },
     { MP_ROM_QSTR(MP_QSTR_write_readinto), MP_ROM_PTR(&rp2pio_statemachine_write_readinto_obj) },
+    { MP_ROM_QSTR(MP_QSTR_background_write), MP_ROM_PTR(&rp2pio_statemachine_background_write_obj) },
+    { MP_ROM_QSTR(MP_QSTR_stop_background_write), MP_ROM_PTR(&rp2pio_statemachine_stop_background_write_obj) },
+    { MP_ROM_QSTR(MP_QSTR_writing), MP_ROM_PTR(&rp2pio_statemachine_writing_obj) },
+    { MP_ROM_QSTR(MP_QSTR_pending), MP_ROM_PTR(&rp2pio_statemachine_pending_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_frequency), MP_ROM_PTR(&rp2pio_statemachine_frequency_obj) },
     { MP_ROM_QSTR(MP_QSTR_rxstall), MP_ROM_PTR(&rp2pio_statemachine_rxstall_obj) },
diff --git a/ports/raspberrypi/bindings/rp2pio/StateMachine.h b/ports/raspberrypi/bindings/rp2pio/StateMachine.h
index eb3f4addc5..a77574a57a 100644
--- a/ports/raspberrypi/bindings/rp2pio/StateMachine.h
+++ b/ports/raspberrypi/bindings/rp2pio/StateMachine.h
@@ -65,6 +65,10 @@ void common_hal_rp2pio_statemachine_run(rp2pio_statemachine_obj_t *self, const u
 
 // Writes out the given data.
 bool common_hal_rp2pio_statemachine_write(rp2pio_statemachine_obj_t *self, const uint8_t *data, size_t len, uint8_t stride_in_bytes);
+bool common_hal_rp2pio_statemachine_background_write(rp2pio_statemachine_obj_t *self, const sm_buf_info *once_obj, const sm_buf_info *loop_obj, uint8_t stride_in_bytes);
+bool common_hal_rp2pio_statemachine_stop_background_write(rp2pio_statemachine_obj_t *self);
+mp_int_t common_hal_rp2pio_statemachine_get_pending(rp2pio_statemachine_obj_t *self);
+bool common_hal_rp2pio_statemachine_get_writing(rp2pio_statemachine_obj_t *self);
 bool common_hal_rp2pio_statemachine_readinto(rp2pio_statemachine_obj_t *self, uint8_t *data, size_t len, uint8_t stride_in_bytes);
 bool common_hal_rp2pio_statemachine_write_readinto(rp2pio_statemachine_obj_t *self,
     const uint8_t *data_out, size_t out_len, uint8_t out_stride_in_bytes,
diff --git a/ports/raspberrypi/common-hal/rp2pio/StateMachine.c b/ports/raspberrypi/common-hal/rp2pio/StateMachine.c
index cd1d383008..cfc9442028 100644
--- a/ports/raspberrypi/common-hal/rp2pio/StateMachine.c
+++ b/ports/raspberrypi/common-hal/rp2pio/StateMachine.c
@@ -24,6 +24,8 @@
  * THE SOFTWARE.
  */
 
+#include <string.h>
+
 #include "bindings/rp2pio/StateMachine.h"
 
 #include "common-hal/microcontroller/__init__.h"
@@ -42,6 +44,8 @@
 #include "py/objproperty.h"
 #include "py/runtime.h"
 
+#define NO_DMA_CHANNEL (-1)
+
 // Count how many state machines are using each pin.
 STATIC uint8_t _pin_reference_count[TOTAL_GPIO_COUNT];
 STATIC uint32_t _current_program_id[NUM_PIOS][NUM_PIO_STATE_MACHINES];
@@ -51,6 +55,12 @@ STATIC bool _never_reset[NUM_PIOS][NUM_PIO_STATE_MACHINES];
 
 STATIC uint32_t _current_pins[NUM_PIOS];
 STATIC uint32_t _current_sm_pins[NUM_PIOS][NUM_PIO_STATE_MACHINES];
+STATIC int8_t _sm_dma_plus_one[NUM_PIOS][NUM_PIO_STATE_MACHINES];
+
+#define SM_DMA_ALLOCATED(pio_index, sm) (_sm_dma_plus_one[(pio_index)][(sm)] != 0)
+#define SM_DMA_GET_CHANNEL(pio_index, sm) (_sm_dma_plus_one[(pio_index)][(sm)] - 1)
+#define SM_DMA_CLEAR_CHANNEL(pio_index, sm) (_sm_dma_plus_one[(pio_index)][(sm)] = 0)
+#define SM_DMA_SET_CHANNEL(pio_isntance, sm, channel) (_sm_dma_plus_one[(pio_index)][(sm)] = (channel) + 1)
 
 STATIC PIO pio_instances[2] = {pio0, pio1};
 typedef void (*interrupt_handler_type)(void *);
@@ -70,8 +80,24 @@ static void rp2pio_statemachine_set_pull(uint32_t pull_pin_up, uint32_t pull_pin
     }
 }
 
+STATIC void rp2pio_statemachine_clear_dma(int pio_index, int sm) {
+    if (SM_DMA_ALLOCATED(pio_index, sm)) {
+        int channel = SM_DMA_GET_CHANNEL(pio_index, sm);
+        uint32_t channel_mask = 1u << channel;
+        dma_hw->inte0 &= ~channel_mask;
+        if (!dma_hw->inte0) {
+            irq_set_mask_enabled(1 << DMA_IRQ_0, false);
+        }
+        MP_STATE_PORT(background_pio)[channel] = NULL;
+        dma_channel_abort(channel);
+        dma_channel_unclaim(channel);
+    }
+    SM_DMA_CLEAR_CHANNEL(pio_index, sm);
+}
+
 STATIC void _reset_statemachine(PIO pio, uint8_t sm, bool leave_pins) {
     uint8_t pio_index = pio_get_index(pio);
+    rp2pio_statemachine_clear_dma(pio_index, sm);
     uint32_t program_id = _current_program_id[pio_index][sm];
     if (program_id == 0) {
         return;
@@ -330,6 +356,9 @@ bool rp2pio_statemachine_construct(rp2pio_statemachine_obj_t *self,
     sm_config_set_fifo_join(&c, join);
     self->sm_config = c;
 
+    // no DMA allocated
+    SM_DMA_CLEAR_CHANNEL(pio_index, state_machine);
+
     pio_sm_init(self->pio, self->state_machine, program_offset, &c);
     common_hal_rp2pio_statemachine_run(self, init, init_len);
 
@@ -581,6 +610,7 @@ void common_hal_rp2pio_statemachine_set_frequency(rp2pio_statemachine_obj_t *sel
 
 void rp2pio_statemachine_deinit(rp2pio_statemachine_obj_t *self, bool leave_pins) {
     common_hal_rp2pio_statemachine_stop(self);
+    (void)common_hal_rp2pio_statemachine_stop_background_write(self);
 
     uint8_t sm = self->state_machine;
     uint8_t pio_index = pio_get_index(self->pio);
@@ -848,3 +878,116 @@ uint8_t rp2pio_statemachine_program_offset(rp2pio_statemachine_obj_t *self) {
     uint8_t sm = self->state_machine;
     return _current_program_offset[pio_index][sm];
 }
+
+bool common_hal_rp2pio_statemachine_background_write(rp2pio_statemachine_obj_t *self, const sm_buf_info *once, const sm_buf_info *loop, uint8_t stride_in_bytes) {
+    uint8_t pio_index = pio_get_index(self->pio);
+    uint8_t sm = self->state_machine;
+
+    int pending_buffers = (once->info.buf != NULL) + (loop->info.buf != NULL);
+    if (!once->info.buf) {
+        once = loop;
+    }
+
+
+    if (SM_DMA_ALLOCATED(pio_index, sm)) {
+        if (stride_in_bytes != self->background_stride_in_bytes) {
+            mp_raise_ValueError(translate("Mismatched data size"));
+        }
+
+        while (self->pending_buffers) {
+            RUN_BACKGROUND_TASKS;
+            if (self->user_interruptible && mp_hal_is_interrupted()) {
+                return false;
+            }
+        }
+
+        common_hal_mcu_disable_interrupts();
+        self->once = *once;
+        self->loop = *loop;
+        self->pending_buffers = pending_buffers;
+
+        if (self->dma_completed) {
+            rp2pio_statemachine_dma_complete(self, SM_DMA_GET_CHANNEL(pio_index, sm));
+            self->dma_completed = false;
+        }
+
+        common_hal_mcu_enable_interrupts();
+
+        return true;
+    }
+
+    int channel = dma_claim_unused_channel(false);
+    if (channel == -1) {
+        return false;
+    }
+
+    SM_DMA_SET_CHANNEL(pio_index, sm, channel);
+
+    volatile uint8_t *tx_destination = (volatile uint8_t *)&self->pio->txf[self->state_machine];
+
+    self->tx_dreq = pio_get_dreq(self->pio, self->state_machine, true);
+
+    dma_channel_config c;
+
+    self->current = *once;
+    self->once = *loop;
+    self->loop = *loop;
+    self->pending_buffers = pending_buffers;
+    self->dma_completed = false;
+    self->background_stride_in_bytes = stride_in_bytes;
+
+    c = dma_channel_get_default_config(channel);
+    channel_config_set_transfer_data_size(&c, _stride_to_dma_size(stride_in_bytes));
+    channel_config_set_dreq(&c, self->tx_dreq);
+    channel_config_set_read_increment(&c, true);
+    channel_config_set_write_increment(&c, false);
+    dma_channel_configure(channel, &c,
+        tx_destination,
+        once->info.buf,
+        once->info.len / stride_in_bytes,
+        false);
+
+    common_hal_mcu_disable_interrupts();
+    MP_STATE_PORT(background_pio)[channel] = self;
+    dma_hw->inte0 |= 1u << channel;
+    irq_set_mask_enabled(1 << DMA_IRQ_0, true);
+    dma_start_channel_mask(1u << channel);
+    common_hal_mcu_enable_interrupts();
+
+    return true;
+}
+
+void rp2pio_statemachine_dma_complete(rp2pio_statemachine_obj_t *self, int channel) {
+    self->current = self->once;
+    self->once = self->loop;
+
+    if (self->current.info.buf) {
+        if (self->pending_buffers > 0) {
+            self->pending_buffers--;
+        }
+        dma_channel_set_read_addr(channel, self->current.info.buf, false);
+        dma_channel_set_trans_count(channel, self->current.info.len / self->background_stride_in_bytes, true);
+    } else {
+        self->dma_completed = true;
+        self->pending_buffers = 0; // should be a no-op
+    }
+}
+
+bool common_hal_rp2pio_statemachine_stop_background_write(rp2pio_statemachine_obj_t *self) {
+    uint8_t pio_index = pio_get_index(self->pio);
+    uint8_t sm = self->state_machine;
+    rp2pio_statemachine_clear_dma(pio_index, sm);
+    memset(&self->current, 0, sizeof(self->current));
+    memset(&self->once, 0, sizeof(self->once));
+    memset(&self->loop, 0, sizeof(self->loop));
+    self->pending_buffers = 0;
+    return true;
+}
+
+bool common_hal_rp2pio_statemachine_get_writing(rp2pio_statemachine_obj_t *self) {
+    return !self->dma_completed;
+}
+
+int common_hal_rp2pio_statemachine_get_pending(rp2pio_statemachine_obj_t *self) {
+    return self->pending_buffers;
+}
diff --git a/ports/raspberrypi/common-hal/rp2pio/StateMachine.h b/ports/raspberrypi/common-hal/rp2pio/StateMachine.h
index 0e8e7a3806..470f0ed8b1 100644
--- a/ports/raspberrypi/common-hal/rp2pio/StateMachine.h
+++ b/ports/raspberrypi/common-hal/rp2pio/StateMachine.h
@@ -32,6 +32,11 @@
 #include "common-hal/microcontroller/Pin.h"
 #include "src/rp2_common/hardware_pio/include/hardware/pio.h"
 
+typedef struct sm_buf_info {
+    mp_obj_t obj;
+    mp_buffer_info_t info;
+} sm_buf_info;
+
 typedef struct {
     mp_obj_base_t base;
     uint32_t pins; // Bitmask of what pins this state machine uses.
@@ -54,6 +59,12 @@ typedef struct {
     bool in_shift_right;
     bool user_interruptible;
     uint8_t offset;
+
+    // dma-related items
+    volatile int pending_buffers;
+    sm_buf_info current, once, loop;
+    int background_stride_in_bytes;
+    bool dma_completed;
 } rp2pio_statemachine_obj_t;
 
 void reset_rp2pio_statemachine(void);
@@ -82,6 +93,7 @@ bool rp2pio_statemachine_construct(rp2pio_statemachine_obj_t *self,
 uint8_t rp2pio_statemachine_program_offset(rp2pio_statemachine_obj_t *self);
 
 void rp2pio_statemachine_deinit(rp2pio_statemachine_obj_t *self, bool leave_pins);
+void rp2pio_statemachine_dma_complete(rp2pio_statemachine_obj_t *self, int channel);
 
 extern const mp_obj_type_t rp2pio_statemachine_type;
 
diff --git a/ports/raspberrypi/mpconfigport.h b/ports/raspberrypi/mpconfigport.h
index 0259ffd023..fd09d8a9ac 100644
--- a/ports/raspberrypi/mpconfigport.h
+++ b/ports/raspberrypi/mpconfigport.h
@@ -46,6 +46,7 @@
 #define MICROPY_PORT_ROOT_POINTERS \
     mp_obj_t counting[NUM_PWM_SLICES]; \
     mp_obj_t playing_audio[NUM_DMA_CHANNELS]; \
+    mp_obj_t background_pio[NUM_DMA_CHANNELS]; \
     CIRCUITPY_COMMON_ROOT_POINTERS;
 
 #endif  // __INCLUDED_MPCONFIGPORT_H