diff --git a/.travis.yml b/.travis.yml
index 102fcc17b8..a57c1bfd83 100755
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,9 @@ compiler:
   - gcc
 git:
   depth: 1
+
+# Put a representative board from each port or sub-port near the top
+# to determine more quickly whether that port is going to build or not.
 env:
   - TRAVIS_TEST=unix
   - TRAVIS_TEST=docs
@@ -15,24 +18,25 @@ env:
   - TRAVIS_BOARD=trinket_m0
   - TRAVIS_BOARD=feather_m4_express
   - TRAVIS_BOARD=grandcentral_m4_express
-  - TRAVIS_BOARD=feather_radiofruit_zigbee
   - TRAVIS_BOARD=arduino_zero
   - TRAVIS_BOARD=circuitplayground_express_crickit
-  - TRAVIS_BOARD=feather_m0_basic
   - TRAVIS_BOARD=feather_m0_adalogger
-  - TRAVIS_BOARD=feather_m0_rfm69
-  - TRAVIS_BOARD=feather_m0_rfm9x
+  - TRAVIS_BOARD=feather_m0_basic
   - TRAVIS_BOARD=feather_m0_express
   - TRAVIS_BOARD=feather_m0_express_crickit
+  - TRAVIS_BOARD=feather_m0_rfm69
+  - TRAVIS_BOARD=feather_m0_rfm9x
+  - TRAVIS_BOARD=feather_nrf52832
+  - TRAVIS_BOARD=feather_nrf52840_express
+  - TRAVIS_BOARD=feather_radiofruit_zigbee
+  - TRAVIS_BOARD=gemma_m0
+  - TRAVIS_BOARD=hallowing_m0_express
   - TRAVIS_BOARD=itsybitsy_m0_express
   - TRAVIS_BOARD=itsybitsy_m4_express
   - TRAVIS_BOARD=metro_m0_express
   - TRAVIS_BOARD=metro_m4_express
+  - TRAVIS_BOARD=pca10059
   - TRAVIS_BOARD=pirkey_m0
-  - TRAVIS_BOARD=gemma_m0
-  - TRAVIS_BOARD=hallowing_m0_express
-  - TRAVIS_BOARD=feather_nrf52832
-  - TRAVIS_BOARD=feather_nrf52840_express
   - TRAVIS_BOARD=trellis_m4_express
 
 addons:
diff --git a/ports/atmel-samd/Makefile b/ports/atmel-samd/Makefile
index 11b9a0de67..f8e5051c21 100644
--- a/ports/atmel-samd/Makefile
+++ b/ports/atmel-samd/Makefile
@@ -113,7 +113,7 @@ else
   # -finline-limit=80 or so is similar to not having it on.
   # There is no simple default value, though.
   ifdef INTERNAL_FLASH_FILESYSTEM
-    CFLAGS += -finline-limit=55
+    CFLAGS += -finline-limit=50
   endif
   ifdef CFLAGS_INLINE_LIMIT
     CFLAGS += -finline-limit=$(CFLAGS_INLINE_LIMIT)
diff --git a/ports/atmel-samd/board_busses.c b/ports/atmel-samd/board_busses.c
index e36541ca9f..424c9cc08f 100644
--- a/ports/atmel-samd/board_busses.c
+++ b/ports/atmel-samd/board_busses.c
@@ -34,81 +34,96 @@
 #include "samd/pins.h"
 #include "py/runtime.h"
 
-#if !defined(DEFAULT_I2C_BUS_SDA) || !defined(DEFAULT_I2C_BUS_SCL)
-    STATIC mp_obj_t board_i2c(void) {
-        mp_raise_NotImplementedError(translate("No default I2C bus"));
-        return NULL;
+#define BOARD_I2C (defined(DEFAULT_I2C_BUS_SDA) && defined(DEFAULT_I2C_BUS_SCL))
+#define BOARD_SPI (defined(DEFAULT_SPI_BUS_SCK) && defined(DEFAULT_SPI_BUS_MISO) && defined(DEFAULT_SPI_BUS_MOSI))
+#define BOARD_UART (defined(DEFAULT_UART_BUS_RX) && defined(DEFAULT_UART_BUS_TX))
+
+#if BOARD_I2C
+STATIC mp_obj_t i2c_singleton = NULL;
+
+STATIC mp_obj_t board_i2c(void) {
+
+    if (i2c_singleton == NULL) {
+        busio_i2c_obj_t *self = m_new_obj(busio_i2c_obj_t);
+        self->base.type = &busio_i2c_type;
+
+        assert_pin_free(DEFAULT_I2C_BUS_SDA);
+        assert_pin_free(DEFAULT_I2C_BUS_SCL);
+        common_hal_busio_i2c_construct(self, DEFAULT_I2C_BUS_SCL, DEFAULT_I2C_BUS_SDA, 400000, 0);
+        i2c_singleton = (mp_obj_t)self;
     }
+    return i2c_singleton;
+}
 #else
-    STATIC mp_obj_t i2c_singleton = NULL;
-
-    STATIC mp_obj_t board_i2c(void) {
-
-        if (i2c_singleton == NULL) {
-            busio_i2c_obj_t *self = m_new_obj(busio_i2c_obj_t);
-            self->base.type = &busio_i2c_type;
-
-            assert_pin_free(DEFAULT_I2C_BUS_SDA);
-            assert_pin_free(DEFAULT_I2C_BUS_SCL);
-            common_hal_busio_i2c_construct(self, DEFAULT_I2C_BUS_SCL, DEFAULT_I2C_BUS_SDA, 400000, 0);
-            i2c_singleton = (mp_obj_t)self;
-        }
-        return i2c_singleton;
-
-    }
+STATIC mp_obj_t board_i2c(void) {
+    mp_raise_NotImplementedError(translate("No default I2C bus"));
+    return NULL;
+}
 #endif
 MP_DEFINE_CONST_FUN_OBJ_0(board_i2c_obj, board_i2c);
 
-#if !defined(DEFAULT_SPI_BUS_SCK) || !defined(DEFAULT_SPI_BUS_MISO) || !defined(DEFAULT_SPI_BUS_MOSI)
-    STATIC mp_obj_t board_spi(void) {
-        mp_raise_NotImplementedError(translate("No default SPI bus"));
-        return NULL;
+#if BOARD_SPI
+STATIC mp_obj_t spi_singleton = NULL;
+
+STATIC mp_obj_t board_spi(void) {
+    if (spi_singleton == NULL) {
+        busio_spi_obj_t *self = m_new_obj(busio_spi_obj_t);
+        self->base.type = &busio_spi_type;
+        assert_pin_free(DEFAULT_SPI_BUS_SCK);
+        assert_pin_free(DEFAULT_SPI_BUS_MOSI);
+        assert_pin_free(DEFAULT_SPI_BUS_MISO);
+        const mcu_pin_obj_t* clock = MP_OBJ_TO_PTR(DEFAULT_SPI_BUS_SCK);
+        const mcu_pin_obj_t* mosi = MP_OBJ_TO_PTR(DEFAULT_SPI_BUS_MOSI);
+        const mcu_pin_obj_t* miso = MP_OBJ_TO_PTR(DEFAULT_SPI_BUS_MISO);
+        common_hal_busio_spi_construct(self, clock, mosi, miso);
+        spi_singleton = (mp_obj_t)self;
     }
+    return spi_singleton;
+}
 #else
-    STATIC mp_obj_t spi_singleton = NULL;
-
-    STATIC mp_obj_t board_spi(void) {
-
-        if (spi_singleton == NULL) {
-            busio_spi_obj_t *self = m_new_obj(busio_spi_obj_t);
-            self->base.type = &busio_spi_type;
-            assert_pin_free(DEFAULT_SPI_BUS_SCK);
-            assert_pin_free(DEFAULT_SPI_BUS_MOSI);
-            assert_pin_free(DEFAULT_SPI_BUS_MISO);
-            const mcu_pin_obj_t* clock = MP_OBJ_TO_PTR(DEFAULT_SPI_BUS_SCK);
-            const mcu_pin_obj_t* mosi = MP_OBJ_TO_PTR(DEFAULT_SPI_BUS_MOSI);
-            const mcu_pin_obj_t* miso = MP_OBJ_TO_PTR(DEFAULT_SPI_BUS_MISO);
-            common_hal_busio_spi_construct(self, clock, mosi, miso);
-            spi_singleton = (mp_obj_t)self;
-        }
-        return spi_singleton;
-    }
+STATIC mp_obj_t board_spi(void) {
+    mp_raise_NotImplementedError(translate("No default SPI bus"));
+    return NULL;
+}
 #endif
 MP_DEFINE_CONST_FUN_OBJ_0(board_spi_obj, board_spi);
 
-#if !defined(DEFAULT_UART_BUS_RX) || !defined(DEFAULT_UART_BUS_TX)
-    STATIC mp_obj_t board_uart(void) {
-        mp_raise_NotImplementedError(translate("No default UART bus"));
-        return NULL;
+#if BOARD_UART
+STATIC mp_obj_t uart_singleton = NULL;
+
+STATIC mp_obj_t board_uart(void) {
+    if (uart_singleton == NULL) {
+        busio_uart_obj_t *self = m_new_obj(busio_uart_obj_t);
+        self->base.type = &busio_uart_type;
+
+        assert_pin_free(DEFAULT_UART_BUS_RX);
+        assert_pin_free(DEFAULT_UART_BUS_TX);
+
+        const mcu_pin_obj_t* rx = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_RX);
+        const mcu_pin_obj_t* tx = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_TX);
+
+        common_hal_busio_uart_construct(self, tx, rx, 9600, 8, PARITY_NONE, 1, 1000, 64);
+        uart_singleton = (mp_obj_t)self;
     }
+    return uart_singleton;
+}
 #else
-    STATIC mp_obj_t uart_singleton = NULL;
-
-    STATIC mp_obj_t board_uart(void) {
-        if (uart_singleton == NULL) {
-            busio_uart_obj_t *self = m_new_obj(busio_uart_obj_t);
-            self->base.type = &busio_uart_type;
-
-            assert_pin_free(DEFAULT_UART_BUS_RX);
-            assert_pin_free(DEFAULT_UART_BUS_TX);
-
-            const mcu_pin_obj_t* rx = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_RX);
-            const mcu_pin_obj_t* tx = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_TX);
-
-            common_hal_busio_uart_construct(self, tx, rx, 9600, 8, PARITY_NONE, 1, 1000, 64);
-            uart_singleton = (mp_obj_t)self;
-        }
-        return uart_singleton;
-    }
+STATIC mp_obj_t board_uart(void) {
+    mp_raise_NotImplementedError(translate("No default UART bus"));
+    return NULL;
+}
 #endif
 MP_DEFINE_CONST_FUN_OBJ_0(board_uart_obj, board_uart);
+
+
+void reset_board_busses(void) {
+#if BOARD_I2C
+    i2c_singleton = NULL;
+#endif
+#if BOARD_SPI
+    spi_singleton = NULL;
+#endif
+#if BOARD_UART
+    uart_singleton = NULL;
+#endif
+}
diff --git a/ports/atmel-samd/board_busses.h b/ports/atmel-samd/board_busses.h
index a368885a58..08dd1aae12 100644
--- a/ports/atmel-samd/board_busses.h
+++ b/ports/atmel-samd/board_busses.h
@@ -36,4 +36,6 @@ extern mp_obj_fun_builtin_fixed_t board_spi_obj;
 void board_uart(void);
 extern mp_obj_fun_builtin_fixed_t board_uart_obj;
 
+void reset_board_busses(void);
+
 #endif  // MICROPY_INCLUDED_ATMEL_SAMD_BOARD_BUSSES_H
diff --git a/ports/atmel-samd/boards/hallowing_m0_express/mpconfigboard.h b/ports/atmel-samd/boards/hallowing_m0_express/mpconfigboard.h
index 977ba183f6..8450882b95 100644
--- a/ports/atmel-samd/boards/hallowing_m0_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/hallowing_m0_express/mpconfigboard.h
@@ -62,4 +62,4 @@
 #define IGNORE_PIN_PA24     1
 #define IGNORE_PIN_PA25     1
 
-#define CIRCUITPY_DISPLAYIO
+#define CIRCUITPY_DISPLAYIO    (1)
diff --git a/ports/atmel-samd/common-hal/busio/UART.c b/ports/atmel-samd/common-hal/busio/UART.c
index 005f1897eb..71db7a8afc 100644
--- a/ports/atmel-samd/common-hal/busio/UART.c
+++ b/ports/atmel-samd/common-hal/busio/UART.c
@@ -133,7 +133,13 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 
     if (rx && receiver_buffer_size > 0) {
         self->buffer_length = receiver_buffer_size;
-        self->buffer = (uint8_t *) gc_alloc(self->buffer_length * sizeof(uint8_t), false, false);
+        // Initially allocate the UART's buffer in the long-lived part of the
+        // heap.  UARTs are generally long-lived objects, but the "make long-
+        // lived" machinery is incapable of moving internal pointers like
+        // self->buffer, so do it manually.  (However, as long as internal
+        // pointers like this are NOT moved, allocating the buffer
+        // in the long-lived pool is not strictly necessary)
+        self->buffer = (uint8_t *) gc_alloc(self->buffer_length * sizeof(uint8_t), false, true);
         if (self->buffer == NULL) {
             common_hal_busio_uart_deinit(self);
             mp_raise_msg(&mp_type_MemoryError, translate("Failed to allocate RX buffer"));
@@ -268,7 +274,7 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
 #ifdef MICROPY_VM_HOOK_LOOP
         MICROPY_VM_HOOK_LOOP
 #endif
-       // If we are zero timeout, make sure we don't loop again (in the event 
+       // 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)
             break;
@@ -344,7 +350,18 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
 }
 
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
-    return self->buffer_size;
+    // This assignment is only here because the usart_async routines take a *const argument.
+    struct usart_async_descriptor * const usart_desc_p = (struct usart_async_descriptor * const) &self->usart_desc;
+    struct usart_async_status async_status;
+    usart_async_get_status(usart_desc_p, &async_status);
+    return async_status.rxcnt;
+}
+
+void common_hal_busio_uart_clear_rx_buffer(busio_uart_obj_t *self) {
+    // This assignment is only here because the usart_async routines take a *const argument.
+    struct usart_async_descriptor * const usart_desc_p = (struct usart_async_descriptor * const) &self->usart_desc;
+    usart_async_flush_rx_buffer(usart_desc_p);
+
 }
 
 bool common_hal_busio_uart_ready_to_tx(busio_uart_obj_t *self) {
diff --git a/ports/atmel-samd/common-hal/busio/UART.h b/ports/atmel-samd/common-hal/busio/UART.h
index 685755a5d1..f94df040f8 100644
--- a/ports/atmel-samd/common-hal/busio/UART.h
+++ b/ports/atmel-samd/common-hal/busio/UART.h
@@ -42,10 +42,6 @@ typedef struct {
     bool rx_error;
     uint32_t baudrate;
     uint32_t timeout_ms;
-    // Index of the oldest received character.
-    uint32_t buffer_start;
-    // Index of the next available spot to store a character.
-    uint32_t buffer_size;
     uint32_t buffer_length;
     uint8_t* buffer;
 } busio_uart_obj_t;
diff --git a/ports/atmel-samd/common-hal/neopixel_write/__init__.c b/ports/atmel-samd/common-hal/neopixel_write/__init__.c
index 42813707cd..b30ad47d41 100644
--- a/ports/atmel-samd/common-hal/neopixel_write/__init__.c
+++ b/ports/atmel-samd/common-hal/neopixel_write/__init__.c
@@ -109,16 +109,16 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
         asm("nop; nop;");
         #endif
         #ifdef SAMD51
-        delay_cycles(3);
+        delay_cycles(2);
         #endif
-        if(p & bitMask) {
+        if((p & bitMask) != 0) {
             // This is the high delay unique to a one bit.
             // For the SK6812 its 0.3us
             #ifdef SAMD21
             asm("nop; nop; nop; nop; nop; nop; nop;");
             #endif
             #ifdef SAMD51
-            delay_cycles(11);
+            delay_cycles(3);
             #endif
             *clr = pinMask;
         } else {
@@ -129,7 +129,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
             asm("nop; nop;");
             #endif
             #ifdef SAMD51
-            delay_cycles(3);
+            delay_cycles(2);
             #endif
         }
         if((bitMask >>= 1) != 0) {
@@ -140,7 +140,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
             asm("nop; nop; nop; nop; nop;");
             #endif
             #ifdef SAMD51
-            delay_cycles(20);
+            delay_cycles(4);
             #endif
         } else {
             if(ptr >= end) break;
@@ -151,7 +151,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
             // above operations take.
             // For the SK6812 its 0.6us +- 0.15us
             #ifdef SAMD51
-            delay_cycles(15);
+            delay_cycles(3);
             #endif
         }
     }
diff --git a/ports/atmel-samd/common-hal/pulseio/PWMOut.c b/ports/atmel-samd/common-hal/pulseio/PWMOut.c
index a115a0b732..825bdd1816 100644
--- a/ports/atmel-samd/common-hal/pulseio/PWMOut.c
+++ b/ports/atmel-samd/common-hal/pulseio/PWMOut.c
@@ -52,10 +52,10 @@ uint8_t tcc_refcount[TCC_INST_NUM];
 
 // This bitmask keeps track of which channels of a TCC are currently claimed.
 #ifdef SAMD21
-uint8_t tcc_channels[3] = {0xf0, 0xfc, 0xfc};
+uint8_t tcc_channels[3];   // Set by pwmout_reset() to {0xf0, 0xfc, 0xfc} initially.
 #endif
 #ifdef SAMD51
-uint8_t tcc_channels[5] = {0xc0, 0xf0, 0xf8, 0xfc, 0xfc};
+uint8_t tcc_channels[5];   // Set by pwmout_reset() to {0xc0, 0xf0, 0xf8, 0xfc, 0xfc} initially.
 #endif
 
 void pwmout_reset(void) {
@@ -76,7 +76,7 @@ void pwmout_reset(void) {
         for (uint8_t j = 0; j < tcc_cc_num[i]; j++) {
             mask <<= 1;
         }
-        tcc_channels[i] = 0xf0;
+        tcc_channels[i] = mask;
         tccs[i]->CTRLA.bit.SWRST = 1;
     }
     Tc *tcs[TC_INST_NUM] = TC_INSTS;
@@ -123,7 +123,7 @@ void common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
     // Figure out which timer we are using.
 
     // First see if a tcc is already going with the frequency we want and our
-    // channel is unused. tc's don't have neough channels to share.
+    // channel is unused. tc's don't have enough channels to share.
     const pin_timer_t* timer = NULL;
     uint8_t mux_position = 0;
     if (!variable_frequency) {
@@ -140,6 +140,9 @@ void common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
                 if (tcc->CTRLA.bit.ENABLE == 1 && channel_ok(t)) {
                     timer = t;
                     mux_position = j;
+                    // Claim channel.
+                    tcc_channels[timer->index] |= (1 << tcc_channel(timer));
+
                 }
             }
         }
diff --git a/ports/atmel-samd/supervisor/port.c b/ports/atmel-samd/supervisor/port.c
index f6d968a1cb..2349a74182 100644
--- a/ports/atmel-samd/supervisor/port.c
+++ b/ports/atmel-samd/supervisor/port.c
@@ -61,6 +61,7 @@
 #include "samd/external_interrupts.h"
 #include "samd/dma.h"
 #include "shared-bindings/rtc/__init__.h"
+#include "board_busses.h"
 #include "tick.h"
 #include "usb.h"
 
@@ -278,6 +279,8 @@ void reset_port(void) {
 
     reset_all_pins();
 
+    reset_board_busses();
+
     // Output clocks for debugging.
     // not supported by SAMD51G; uncomment for SAMD51J or update for 51G
     // #ifdef SAMD51
diff --git a/ports/atmel-samd/usb.c b/ports/atmel-samd/usb.c
index f32d81e196..1f1ba550f7 100644
--- a/ports/atmel-samd/usb.c
+++ b/ports/atmel-samd/usb.c
@@ -288,7 +288,7 @@ void usb_write(const char* buffer, uint32_t len) {
         return;
     }
     uint8_t * output_buffer;
-    uint8_t output_len;
+    uint32_t output_len;
     while (len > 0) {
         while (usb_transmitting) {}
         output_buffer = (uint8_t *) buffer;
diff --git a/ports/esp8266/common-hal/busio/UART.c b/ports/esp8266/common-hal/busio/UART.c
index 7a4ca6e0df..e68e739f3a 100644
--- a/ports/esp8266/common-hal/busio/UART.c
+++ b/ports/esp8266/common-hal/busio/UART.c
@@ -138,6 +138,9 @@ uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     return 0;
 }
 
+void common_hal_busio_uart_clear_rx_buffer(busio_uart_obj_t *self) {
+}
+
 bool common_hal_busio_uart_ready_to_tx(busio_uart_obj_t *self) {
     return true;
 }
diff --git a/ports/nrf/common-hal/busio/UART.c b/ports/nrf/common-hal/busio/UART.c
index f05949e152..270c92f472 100644
--- a/ports/nrf/common-hal/busio/UART.c
+++ b/ports/nrf/common-hal/busio/UART.c
@@ -82,6 +82,10 @@ uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     return 0;
 }
 
+void common_hal_busio_uart_clear_rx_buffer(busio_uart_obj_t *self) {
+    mp_raise_NotImplementedError("busio.UART not yet implemented");
+}
+
 bool common_hal_busio_uart_ready_to_tx(busio_uart_obj_t *self) {
     mp_raise_NotImplementedError(translate("busio.UART not yet implemented"));
     return false;
diff --git a/shared-bindings/busio/UART.c b/shared-bindings/busio/UART.c
index 359334e5c5..e7b8fc0c5b 100644
--- a/shared-bindings/busio/UART.c
+++ b/shared-bindings/busio/UART.c
@@ -67,7 +67,11 @@ extern const busio_uart_parity_obj_t busio_uart_parity_odd_obj;
 
 STATIC mp_obj_t busio_uart_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *pos_args) {
     mp_arg_check_num(n_args, n_kw, 0, MP_OBJ_FUN_ARGS_MAX, true);
-    busio_uart_obj_t *self = m_new_obj(busio_uart_obj_t);
+    // Always initially allocate the UART object within the long-lived heap.
+    // This is needed to avoid crashes with certain UART implementations which
+    // cannot accomodate being moved after creation. (See
+    // https://github.com/adafruit/circuitpython/issues/1056)
+    busio_uart_obj_t *self = m_new_ll_obj(busio_uart_obj_t);
     self->base.type = &busio_uart_type;
     mp_map_t kw_args;
     mp_map_init_fixed_table(&kw_args, n_kw, pos_args + n_args);
@@ -249,6 +253,36 @@ const mp_obj_property_t busio_uart_baudrate_obj = {
               (mp_obj_t)&mp_const_none_obj},
 };
 
+//|   .. attribute:: in_waiting
+//|
+//|     The number of bytes in the input buffer, available to be read
+//|
+STATIC mp_obj_t busio_uart_obj_get_in_waiting(mp_obj_t self_in) {
+    busio_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    raise_error_if_deinited(common_hal_busio_uart_deinited(self));
+    return MP_OBJ_NEW_SMALL_INT(common_hal_busio_uart_rx_characters_available(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(busio_uart_get_in_waiting_obj, busio_uart_obj_get_in_waiting);
+
+const mp_obj_property_t busio_uart_in_waiting_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&busio_uart_get_in_waiting_obj,
+              (mp_obj_t)&mp_const_none_obj,
+              (mp_obj_t)&mp_const_none_obj},
+};
+
+//|   .. method:: reset_input_buffer()
+//|
+//|     Discard any unread characters in the input buffer.
+//|
+STATIC mp_obj_t busio_uart_obj_reset_input_buffer(mp_obj_t self_in) {
+    busio_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    raise_error_if_deinited(common_hal_busio_uart_deinited(self));
+    common_hal_busio_uart_clear_rx_buffer(self);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(busio_uart_reset_input_buffer_obj, busio_uart_obj_reset_input_buffer);
+
 //| .. class:: busio.UART.Parity
 //|
 //|     Enum-like class to define the parity used to verify correct data transfer.
@@ -303,8 +337,11 @@ STATIC const mp_rom_map_elem_t busio_uart_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&mp_stream_readinto_obj) },
     { MP_OBJ_NEW_QSTR(MP_QSTR_write),    MP_ROM_PTR(&mp_stream_write_obj) },
 
+    { MP_OBJ_NEW_QSTR(MP_QSTR_reset_input_buffer), MP_ROM_PTR(&busio_uart_reset_input_buffer_obj) },
+
     // Properties
     { MP_ROM_QSTR(MP_QSTR_baudrate), MP_ROM_PTR(&busio_uart_baudrate_obj) },
+    { MP_ROM_QSTR(MP_QSTR_in_waiting), MP_ROM_PTR(&busio_uart_in_waiting_obj) },
 
     // Nested Enum-like Classes.
     { MP_ROM_QSTR(MP_QSTR_Parity),       MP_ROM_PTR(&busio_uart_parity_type) },
diff --git a/shared-bindings/busio/UART.h b/shared-bindings/busio/UART.h
index fa39d8ad5f..513ff50c83 100644
--- a/shared-bindings/busio/UART.h
+++ b/shared-bindings/busio/UART.h
@@ -60,6 +60,7 @@ extern void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t
 
 
 extern uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self);
+extern void common_hal_busio_uart_clear_rx_buffer(busio_uart_obj_t *self);
 extern bool common_hal_busio_uart_ready_to_tx(busio_uart_obj_t *self);
 
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_BUSIO_UART_H
diff --git a/tools/build_adafruit_bins.sh b/tools/build_adafruit_bins.sh
index e0899ba701..e7b9644aa7 100755
--- a/tools/build_adafruit_bins.sh
+++ b/tools/build_adafruit_bins.sh
@@ -2,6 +2,7 @@ rm -rf ports/atmel-samd/build*
 rm -rf ports/esp8266/build*
 rm -rf ports/nrf/build*
 
+# Alphabetical.
 HW_BOARDS="\
 arduino_zero \
 circuitplayground_express \
@@ -16,18 +17,19 @@ feather_m0_rfm9x \
 feather_m4_express \
 feather_nrf52832 \
 feather_nrf52840_express \
-grandcentral_m4_express \
-pca10056 \
 feather_radiofruit_zigbee \
 gemma_m0 \
+grandcentral_m4_express \
 hallowing_m0_express \
 itsybitsy_m0_express \
 itsybitsy_m4_express \
 metro_m0_express \
 metro_m4_express \
+pca10056 \
+pca10059 \
 pirkey_m0 \
-trinket_m0 \
 trellis_m4_express \
+trinket_m0 \
 "
 ROSIE_SETUPS="rosie-ci"