diff --git a/ports/nrf/common-hal/neopixel_write/__init__.c b/ports/nrf/common-hal/neopixel_write/__init__.c
index 8495a359d..0a4036aae 100644
--- a/ports/nrf/common-hal/neopixel_write/__init__.c
+++ b/ports/nrf/common-hal/neopixel_write/__init__.c
@@ -25,6 +25,7 @@
  */
 
 #include "py/mphal.h"
+#include "py/mpstate.h"
 #include "shared-bindings/neopixel_write/__init__.h"
 #include "nrf_pwm.h"
 
@@ -97,6 +98,13 @@ static NRF_PWM_Type* find_free_pwm (void) {
     return NULL;
 }
 
+static size_t pixels_pattern_heap_size = 0;
+// Called during reset_port() to free the pattern buffer
+void neopixel_write_reset(void) {
+    MP_STATE_VM(pixels_pattern_heap) = NULL;
+    pixels_pattern_heap_size = 0;
+}
+
 uint64_t next_start_tick_ms = 0;
 uint32_t next_start_tick_us = 1000;
 
@@ -119,10 +127,8 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
 // We need space for at least 10 pixels for Circuit Playground, but let's choose 24
 // to handle larger NeoPixel rings without malloc'ing.
 #define STACK_PIXELS 24
-
     uint32_t pattern_size = PATTERN_SIZE(numBytes);
     uint16_t* pixels_pattern = NULL;
-    bool pattern_on_heap = false;
 
     // Use the stack to store STACK_PIXEL's worth of PWM data. uint32_t to ensure alignment.
     // It is 3*STACK_PIXELS to handle RGB.
@@ -138,16 +144,34 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
         } else {
             uint8_t sd_en = 0;
             (void) sd_softdevice_is_enabled(&sd_en);
-            if (sd_en) {
-                // If the soft device is enabled then we must use PWM to
-                // transmit. This takes a bunch of memory to do so raise an
-                // exception if we can't.
-                pixels_pattern = (uint16_t *) m_malloc(pattern_size, false);
-            } else {
-                pixels_pattern = (uint16_t *) m_malloc_maybe(pattern_size, false);
-            }
 
-            pattern_on_heap = true;
+            if (pixels_pattern_heap_size < pattern_size) {
+                // Current heap buffer is too small.
+                if (MP_STATE_VM(pixels_pattern_heap)) {
+                    // Old pixels_pattern_heap will be gc'd; don't free it.
+                    pixels_pattern = NULL;
+                    pixels_pattern_heap_size = 0;
+                }
+
+                // realloc routines fall back to a plain malloc if the incoming ptr is NULL.
+                if (sd_en) {
+                    // If the soft device is enabled then we must use PWM to
+                    // transmit. This takes a bunch of memory to do so raise an
+                    // exception if we can't.
+                    MP_STATE_VM(pixels_pattern_heap) =
+                        (uint16_t *) m_realloc(MP_STATE_VM(pixels_pattern_heap), pattern_size);
+                } else {
+                    // Might return NULL.
+                    MP_STATE_VM(pixels_pattern_heap) =
+                        // true means move if necessary.
+                        (uint16_t *) m_realloc_maybe(MP_STATE_VM(pixels_pattern_heap), pattern_size, true);
+                }
+                if (MP_STATE_VM(pixels_pattern_heap)) {
+                    pixels_pattern_heap_size = pattern_size;
+                }
+            }
+            // Might be NULL, which means we failed to allocate.
+            pixels_pattern = MP_STATE_VM(pixels_pattern_heap);
         }
     }
 
@@ -155,7 +179,7 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
     wait_until(next_start_tick_ms, next_start_tick_us);
 
     // Use the identified device to choose the implementation
-    // If a PWM device is available use DMA
+    // If a PWM device is available and we have a buffer, use DMA.
     if ( (pixels_pattern != NULL) && (pwm != NULL) ) {
         uint16_t pos = 0;  // bit position
 
@@ -229,10 +253,6 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
         nrf_pwm_disable(pwm);
         nrf_pwm_pins_set(pwm, (uint32_t[]) {0xFFFFFFFFUL, 0xFFFFFFFFUL, 0xFFFFFFFFUL, 0xFFFFFFFFUL} );
 
-        if (pattern_on_heap) {
-            m_free(pixels_pattern);
-        }
-
     } // End of DMA implementation
     // ---------------------------------------------------------------------
     else {
diff --git a/ports/nrf/common-hal/neopixel_write/__init__.h b/ports/nrf/common-hal/neopixel_write/__init__.h
new file mode 100644
index 000000000..b8dce85ad
--- /dev/null
+++ b/ports/nrf/common-hal/neopixel_write/__init__.h
@@ -0,0 +1,32 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Lucian Copeland 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_STM32F4_COMMON_HAL_NEOPIXEL_WRITE_INIT_H
+#define MICROPY_INCLUDED_STM32F4_COMMON_HAL_NEOPIXEL_WRITE_INIT_H
+
+void neopixel_write_reset(void);
+
+#endif // MICROPY_INCLUDED_STM32F4_COMMON_HAL_NEOPIXEL_WRITE_INIT_H
\ No newline at end of file
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 473169e94..44e51fc5f 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -164,6 +164,7 @@
 
 #define MICROPY_PORT_ROOT_POINTERS \
     CIRCUITPY_COMMON_ROOT_POINTERS \
+    uint16_t* pixels_pattern_heap; \
     ble_drv_evt_handler_entry_t* ble_drv_evt_handler_entries; \
 
 
diff --git a/ports/nrf/supervisor/port.c b/ports/nrf/supervisor/port.c
index 6a4813c66..cbe0cec54 100644
--- a/ports/nrf/supervisor/port.c
+++ b/ports/nrf/supervisor/port.c
@@ -47,6 +47,7 @@
 #include "common-hal/pulseio/PulseOut.h"
 #include "common-hal/pulseio/PulseIn.h"
 #include "common-hal/rtc/RTC.h"
+#include "common-hal/neopixel_write/__init__.h"
 #include "tick.h"
 
 #include "shared-bindings/rtc/__init__.h"
@@ -103,6 +104,7 @@ void reset_port(void) {
     i2c_reset();
     spi_reset();
     uart_reset();
+    neopixel_write_reset();
 
 #if CIRCUITPY_AUDIOBUSIO
     i2s_reset();