make UART.write be blocking on SAMD; add timeout property

9 files changed, 144 insertions, 85 deletions

diff --git a/ports/atmel-samd/common-hal/busio/UART.c b/ports/atmel-samd/common-hal/busio/UART.c
index 2505e894a..d869f70ff 100644
--- a/ports/atmel-samd/common-hal/busio/UART.c
+++ b/ports/atmel-samd/common-hal/busio/UART.c
@@ -323,29 +323,23 @@ size_t common_hal_busio_uart_write(busio_uart_obj_t *self, const uint8_t *data,
     struct io_descriptor *io;
     usart_async_get_io_descriptor(usart_desc_p, &io);
 
+    // Start writing characters. This is non-blocking and will
+    // return immediately after setting up the write.
     if (io_write(io, data, len) < 0) {
         *errcode = MP_EAGAIN;
         return MP_STREAM_ERROR;
     }
 
-    // Wait until write is complete or timeout.
-    bool done = false;
-    uint64_t start_ticks = ticks_ms;
-    // Busy-wait for timeout.
-    while (ticks_ms - start_ticks < self->timeout_ms) {
-        if (usart_async_is_tx_empty(usart_desc_p)) {
-            done = true;
+    // Busy-wait until all characters transmitted.
+    struct usart_async_status async_status;
+    while (true) {
+        usart_async_get_status(usart_desc_p, &async_status);
+        if (async_status.txcnt >= len) {
             break;
         }
         RUN_BACKGROUND_TASKS;
     }
 
-    if (!done) {
-        *errcode = MP_EAGAIN;
-        return MP_STREAM_ERROR;
-    }
-
-    // All the characters got written.
     return len;
 }
 
@@ -368,6 +362,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     self->baudrate = baudrate;
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout_ms / 1000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_ms = timeout * 1000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(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;
@@ -383,12 +385,14 @@ void common_hal_busio_uart_clear_rx_buffer(busio_uart_obj_t *self) {
 
 }
 
+// True if there are no characters still to be written.
 bool common_hal_busio_uart_ready_to_tx(busio_uart_obj_t *self) {
     if (self->tx_pin == NO_PIN) {
         return false;
     }
     // This assignment is only here because the usart_async routines take a *const argument.
-    const struct _usart_async_device * const usart_device_p =
-        (struct _usart_async_device * const) &self->usart_desc.device;
-    return _usart_async_is_byte_sent(usart_device_p);
+    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.flags & USART_ASYNC_STATUS_BUSY);
 }
diff --git a/ports/cxd56/common-hal/busio/UART.c b/ports/cxd56/common-hal/busio/UART.c
index 4a1376f19..6ae2403c1 100644
--- a/ports/cxd56/common-hal/busio/UART.c
+++ b/ports/cxd56/common-hal/busio/UART.c
@@ -102,7 +102,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     self->tx_pin = tx;
     self->rx_pin = rx;
     self->baudrate = baudrate;
-    self->timeout = timeout;
+    self->timeout_us = timeout * 1000000;
 }
 
 void common_hal_busio_uart_deinit(busio_uart_obj_t *self) {
@@ -135,7 +135,7 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
     FD_SET(busio_uart_dev[self->number].fd, &rfds);
 
     tv.tv_sec = 0;
-    tv.tv_usec = self->timeout * 1000;
+    tv.tv_usec = self->timeout_us;
 
     retval = select(busio_uart_dev[self->number].fd + 1, &rfds, NULL, NULL, &tv);
 
@@ -172,6 +172,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     ioctl(busio_uart_dev[self->number].fd, TCFLSH, (long unsigned int)NULL);
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout / 1000000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_us = timeout * 1000000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     int count = 0;
 
diff --git a/ports/cxd56/common-hal/busio/UART.h b/ports/cxd56/common-hal/busio/UART.h
index e1d816149..a69c47056 100644
--- a/ports/cxd56/common-hal/busio/UART.h
+++ b/ports/cxd56/common-hal/busio/UART.h
@@ -37,7 +37,7 @@ typedef struct {
     const mcu_pin_obj_t *tx_pin;
     const mcu_pin_obj_t *rx_pin;
     uint32_t baudrate;
-    uint32_t timeout;
+    uint32_t timeout_us;
 } busio_uart_obj_t;
 
 void busio_uart_reset(void);
diff --git a/ports/nrf/common-hal/busio/UART.c b/ports/nrf/common-hal/busio/UART.c
index 54a66ddbe..a0ae8af00 100644
--- a/ports/nrf/common-hal/busio/UART.c
+++ b/ports/nrf/common-hal/busio/UART.c
@@ -265,19 +265,6 @@ size_t common_hal_busio_uart_write (busio_uart_obj_t *self, const uint8_t *data,
 
     if ( len == 0 ) return 0;
 
-    uint64_t start_ticks = ticks_ms;
-
-    // Wait for on-going transfer to complete
-    while ( nrfx_uarte_tx_in_progress(self->uarte) && (ticks_ms - start_ticks < self->timeout_ms) ) {
-        RUN_BACKGROUND_TASKS;
-    }
-
-    // Time up
-    if ( !(ticks_ms - start_ticks < self->timeout_ms) ) {
-        *errcode = MP_EAGAIN;
-        return MP_STREAM_ERROR;
-    }
-
     // EasyDMA can only access SRAM
     uint8_t * tx_buf = (uint8_t*) data;
     if ( !nrfx_is_in_ram(data) ) {
@@ -290,7 +277,8 @@ size_t common_hal_busio_uart_write (busio_uart_obj_t *self, const uint8_t *data,
     _VERIFY_ERR(*errcode);
     (*errcode) = 0;
 
-    while ( nrfx_uarte_tx_in_progress(self->uarte) && (ticks_ms - start_ticks < self->timeout_ms) ) {
+    // Wait for write to complete.
+    while ( nrfx_uarte_tx_in_progress(self->uarte) ) {
         RUN_BACKGROUND_TASKS;
     }
 
@@ -310,6 +298,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     nrf_uarte_baudrate_set(self->uarte->p_reg, get_nrf_baud(baudrate));
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout_ms / 1000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_ms = timeout * 1000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     return ringbuf_count(&self->rbuf);
 }
diff --git a/ports/stm32f4/common-hal/busio/UART.c b/ports/stm32f4/common-hal/busio/UART.c
index c4ab237cd..f0e0cc9eb 100644
--- a/ports/stm32f4/common-hal/busio/UART.c
+++ b/ports/stm32f4/common-hal/busio/UART.c
@@ -36,7 +36,7 @@
 #include "supervisor/shared/translate.h"
 
 #include "tick.h"
-#include "stm32f4xx_hal.h" 
+#include "stm32f4xx_hal.h"
 
 #define ALL_UARTS 0xFFFF
 
@@ -55,7 +55,7 @@ void uart_reset(void) {
     uart_clock_disable(ALL_UARTS);
 }
 
-STATIC USART_TypeDef * assign_uart_or_throw(busio_uart_obj_t* self, bool pin_eval, 
+STATIC USART_TypeDef * assign_uart_or_throw(busio_uart_obj_t* self, bool pin_eval,
                                             int uart_index, bool uart_taken) {
     if (pin_eval) {
         //assign a root pointer pointer for IRQ
@@ -82,7 +82,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
     uint8_t rx_len = sizeof(mcu_uart_rx_list)/sizeof(*mcu_uart_rx_list);
     bool uart_taken = false;
     uint8_t uart_index = 0; //origin 0 corrected
-    
+
     //Can have both pins, or either
     if ((tx != mp_const_none) && (rx != mp_const_none)) {
         //normal find loop if both pins exist
@@ -90,7 +90,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
             if (mcu_uart_tx_list[i].pin == tx) {
                 //rx
                 for (uint j = 0; j < rx_len; j++) {
-                    if (mcu_uart_rx_list[j].pin == rx 
+                    if (mcu_uart_rx_list[j].pin == rx
                         && mcu_uart_rx_list[j].uart_index == mcu_uart_tx_list[i].uart_index) {
                         //keep looking if the UART is taken, edge case
                         if (reserved_uart[mcu_uart_tx_list[i].uart_index - 1]) {
@@ -106,7 +106,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
             }
         }
         uart_index = self->tx->uart_index - 1;
-        USARTx = assign_uart_or_throw(self, (self->tx != NULL && self->rx != NULL), 
+        USARTx = assign_uart_or_throw(self, (self->tx != NULL && self->rx != NULL),
             uart_index, uart_taken);
     } else if (tx == mp_const_none) {
         //If there is no tx, run only rx
@@ -123,7 +123,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
             }
         }
         uart_index = self->rx->uart_index - 1;
-        USARTx = assign_uart_or_throw(self, (self->rx != NULL), 
+        USARTx = assign_uart_or_throw(self, (self->rx != NULL),
             uart_index, uart_taken);
     } else if (rx == mp_const_none) {
         //If there is no rx, run only tx
@@ -140,7 +140,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
             }
         }
         uart_index = self->tx->uart_index - 1;
-        USARTx = assign_uart_or_throw(self, (self->tx != NULL), 
+        USARTx = assign_uart_or_throw(self, (self->tx != NULL),
             uart_index, uart_taken);
     } else {
         //both pins cannot be empty
@@ -173,7 +173,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
         GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
         GPIO_InitStruct.Pull = GPIO_PULLUP;
         GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
-        GPIO_InitStruct.Alternate = self->rx->altfn_index; 
+        GPIO_InitStruct.Alternate = self->rx->altfn_index;
         HAL_GPIO_Init(pin_port(rx->port), &GPIO_InitStruct);
     }
 
@@ -186,7 +186,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t* self,
     self->handle.Init.BaudRate = baudrate;
     self->handle.Init.WordLength = (bits == 9) ? UART_WORDLENGTH_9B : UART_WORDLENGTH_8B;
     self->handle.Init.StopBits = (stop > 1) ? UART_STOPBITS_2 : UART_STOPBITS_1;
-    self->handle.Init.Parity = (parity == PARITY_ODD) ? UART_PARITY_ODD : 
+    self->handle.Init.Parity = (parity == PARITY_ODD) ? UART_PARITY_ODD :
                                (parity == PARITY_EVEN) ? UART_PARITY_EVEN :
                                UART_PARITY_NONE;
     self->handle.Init.Mode = (self->tx != NULL && self->rx != NULL) ? UART_MODE_TX_RX :
@@ -234,7 +234,7 @@ bool common_hal_busio_uart_deinited(busio_uart_obj_t *self) {
 
 void common_hal_busio_uart_deinit(busio_uart_obj_t *self) {
     if (common_hal_busio_uart_deinited(self)) return;
-    
+
     reset_pin_number(self->tx->pin->port,self->tx->pin->number);
     reset_pin_number(self->rx->pin->port,self->rx->pin->number);
     self->tx = mp_const_none;
@@ -279,7 +279,7 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
         *errcode = EAGAIN;
         return MP_STREAM_ERROR;
     }
-    return rx_bytes; 
+    return rx_bytes;
 }
 
 // Write characters.
@@ -290,13 +290,15 @@ size_t common_hal_busio_uart_write(busio_uart_obj_t *self, const uint8_t *data,
     bool write_err = false; //write error shouldn't disable interrupts
 
     HAL_NVIC_DisableIRQ(self->irq);
-    if (HAL_UART_Transmit(&self->handle, (uint8_t*)data, len, self->timeout_ms) != HAL_OK) {
+    if (HAL_UART_Transmit(&self->handle, (uint8_t*)data, len, HAL_MAX_DELAY) != HAL_OK) {
         write_err = true;
     }
     HAL_UART_Receive_IT(&self->handle, &self->rx_char, 1);
     HAL_NVIC_EnableIRQ(self->irq);
 
-    if (write_err) mp_raise_ValueError(translate("UART write error"));
+    if (write_err) {
+        mp_raise_ValueError(translate("UART write error"));
+    }
     return len;
 }
 
@@ -312,7 +314,7 @@ void HAL_UART_RxCpltCallback(UART_HandleTypeDef *handle)
             }
             ringbuf_put_n(&context->rbuf, &context->rx_char, 1);
             errflag = HAL_UART_Receive_IT(handle, &context->rx_char, 1);
-            
+
             return;
         }
     }
@@ -360,6 +362,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     self->baudrate = baudrate;
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout_ms / 1000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_ms = timeout * 1000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     return ringbuf_count(&self->rbuf);
 }
@@ -414,71 +424,71 @@ STATIC void uart_clock_enable(uint16_t mask) {
     if (mask & (1 << 0)) {
         __HAL_RCC_USART1_FORCE_RESET();
         __HAL_RCC_USART1_RELEASE_RESET();
-        __HAL_RCC_USART1_CLK_ENABLE(); 
+        __HAL_RCC_USART1_CLK_ENABLE();
     }
     #endif
     #ifdef USART2
     if (mask & (1 << 1)) {
         __HAL_RCC_USART2_FORCE_RESET();
         __HAL_RCC_USART2_RELEASE_RESET();
-        __HAL_RCC_USART2_CLK_ENABLE(); 
+        __HAL_RCC_USART2_CLK_ENABLE();
     }
     #endif
     #ifdef USART3
     if (mask & (1 << 2)) {
         __HAL_RCC_USART3_FORCE_RESET();
         __HAL_RCC_USART3_RELEASE_RESET();
-        __HAL_RCC_USART3_CLK_ENABLE(); 
+        __HAL_RCC_USART3_CLK_ENABLE();
     }
     #endif
     #ifdef UART4
     if (mask & (1 << 3)) {
         __HAL_RCC_UART4_FORCE_RESET();
         __HAL_RCC_UART4_RELEASE_RESET();
-        __HAL_RCC_UART4_CLK_ENABLE(); 
+        __HAL_RCC_UART4_CLK_ENABLE();
     }
     #endif
     #ifdef UART5
     if (mask & (1 << 4)) {
         __HAL_RCC_UART5_FORCE_RESET();
         __HAL_RCC_UART5_RELEASE_RESET();
-        __HAL_RCC_UART5_CLK_ENABLE(); 
+        __HAL_RCC_UART5_CLK_ENABLE();
     }
     #endif
     #ifdef USART6
     if (mask & (1 << 5)) {
         __HAL_RCC_USART6_FORCE_RESET();
         __HAL_RCC_USART6_RELEASE_RESET();
-        __HAL_RCC_USART6_CLK_ENABLE(); 
-    } 
+        __HAL_RCC_USART6_CLK_ENABLE();
+    }
     #endif
     #ifdef UART7
     if (mask & (1 << 6)) {
         __HAL_RCC_UART7_FORCE_RESET();
         __HAL_RCC_UART7_RELEASE_RESET();
-        __HAL_RCC_UART7_CLK_ENABLE(); 
-    } 
+        __HAL_RCC_UART7_CLK_ENABLE();
+    }
     #endif
     #ifdef UART8
     if (mask & (1 << 7)) {
         __HAL_RCC_UART8_FORCE_RESET();
         __HAL_RCC_UART8_RELEASE_RESET();
-        __HAL_RCC_UART8_CLK_ENABLE(); 
-    } 
+        __HAL_RCC_UART8_CLK_ENABLE();
+    }
     #endif
     #ifdef UART9
     if (mask & (1 << 8)) {
         __HAL_RCC_UART9_FORCE_RESET();
         __HAL_RCC_UART9_RELEASE_RESET();
-        __HAL_RCC_UART9_CLK_ENABLE(); 
-    } 
+        __HAL_RCC_UART9_CLK_ENABLE();
+    }
     #endif
     #ifdef UART10
     if (mask & (1 << 9)) {
         __HAL_RCC_UART10_FORCE_RESET();
         __HAL_RCC_UART10_RELEASE_RESET();
-        __HAL_RCC_UART10_CLK_ENABLE(); 
-    } 
+        __HAL_RCC_UART10_CLK_ENABLE();
+    }
     #endif
 }
 
@@ -487,71 +497,71 @@ STATIC void uart_clock_disable(uint16_t mask) {
     if (mask & (1 << 0)) {
         __HAL_RCC_USART1_FORCE_RESET();
         __HAL_RCC_USART1_RELEASE_RESET();
-        __HAL_RCC_USART1_CLK_DISABLE(); 
+        __HAL_RCC_USART1_CLK_DISABLE();
     }
     #endif
     #ifdef USART2
     if (mask & (1 << 1)) {
         __HAL_RCC_USART2_FORCE_RESET();
         __HAL_RCC_USART2_RELEASE_RESET();
-        __HAL_RCC_USART2_CLK_DISABLE(); 
+        __HAL_RCC_USART2_CLK_DISABLE();
     }
     #endif
     #ifdef USART3
     if (mask & (1 << 2)) {
         __HAL_RCC_USART3_FORCE_RESET();
         __HAL_RCC_USART3_RELEASE_RESET();
-        __HAL_RCC_USART3_CLK_DISABLE(); 
+        __HAL_RCC_USART3_CLK_DISABLE();
     }
     #endif
     #ifdef UART4
     if (mask & (1 << 3)) {
         __HAL_RCC_UART4_FORCE_RESET();
         __HAL_RCC_UART4_RELEASE_RESET();
-        __HAL_RCC_UART4_CLK_DISABLE(); 
+        __HAL_RCC_UART4_CLK_DISABLE();
     }
     #endif
     #ifdef UART5
     if (mask & (1 << 4)) {
         __HAL_RCC_UART5_FORCE_RESET();
         __HAL_RCC_UART5_RELEASE_RESET();
-        __HAL_RCC_UART5_CLK_DISABLE(); 
+        __HAL_RCC_UART5_CLK_DISABLE();
     }
     #endif
     #ifdef USART6
     if (mask & (1 << 5)) {
         __HAL_RCC_USART6_FORCE_RESET();
         __HAL_RCC_USART6_RELEASE_RESET();
-        __HAL_RCC_USART6_CLK_DISABLE(); 
-    } 
+        __HAL_RCC_USART6_CLK_DISABLE();
+    }
     #endif
     #ifdef UART7
     if (mask & (1 << 6)) {
         __HAL_RCC_UART7_FORCE_RESET();
         __HAL_RCC_UART7_RELEASE_RESET();
-        __HAL_RCC_UART7_CLK_DISABLE(); 
-    } 
+        __HAL_RCC_UART7_CLK_DISABLE();
+    }
     #endif
     #ifdef UART8
     if (mask & (1 << 7)) {
         __HAL_RCC_UART8_FORCE_RESET();
         __HAL_RCC_UART8_RELEASE_RESET();
-        __HAL_RCC_UART8_CLK_DISABLE(); 
-    } 
+        __HAL_RCC_UART8_CLK_DISABLE();
+    }
     #endif
     #ifdef UART9
     if (mask & (1 << 8)) {
         __HAL_RCC_UART9_FORCE_RESET();
         __HAL_RCC_UART9_RELEASE_RESET();
-        __HAL_RCC_UART9_CLK_DISABLE(); 
-    } 
+        __HAL_RCC_UART9_CLK_DISABLE();
+    }
     #endif
     #ifdef UART10
     if (mask & (1 << 9)) {
         __HAL_RCC_UART10_FORCE_RESET();
         __HAL_RCC_UART10_RELEASE_RESET();
-        __HAL_RCC_UART10_CLK_DISABLE(); 
-    } 
+        __HAL_RCC_UART10_CLK_DISABLE();
+    }
     #endif
 }
 
diff --git a/shared-bindings/board/__init__.c b/shared-bindings/board/__init__.c
index 47e2d64bc..3dda59fb8 100644
--- a/shared-bindings/board/__init__.c
+++ b/shared-bindings/board/__init__.c
@@ -93,6 +93,12 @@ MP_DEFINE_CONST_FUN_OBJ_0(board_spi_obj, board_spi);
 //|
 //|   Returns the `busio.UART` object for the board designated TX and RX pins. It is a singleton.
 //|
+//|   The object created uses the default parameter values for `busio.UART`. If you need to set
+//|   parameters that are not changeable after creation, such as ``receiver_buffer_size``,
+//|   do not use `board.UART()`; instead create a `busio.UART` object explicitly with the
+//|   desired parameters.
+//|
+//|
 #if BOARD_UART
 mp_obj_t board_uart(void) {
     mp_obj_t singleton = common_hal_board_get_uart();
diff --git a/shared-bindings/busio/UART.c b/shared-bindings/busio/UART.c
index c7eef8c43..9606c77e9 100644
--- a/shared-bindings/busio/UART.c
+++ b/shared-bindings/busio/UART.c
@@ -57,7 +57,7 @@
 //|   :param int bits:  the number of bits per byte, 7, 8 or 9.
 //|   :param Parity parity:  the parity used for error checking.
 //|   :param int stop:  the number of stop bits, 1 or 2.
-//|   :param float timeout:  the timeout in seconds to wait for the first character and between subsequent characters. Raises ``ValueError`` if timeout >100 seconds.
+//|   :param float timeout:  the timeout in seconds to wait for the first character and between subsequent characters when reading. Raises ``ValueError`` if timeout >100 seconds.
 //|   :param int receiver_buffer_size: the character length of the read buffer (0 to disable). (When a character is 9 bits the buffer will be 2 * receiver_buffer_size bytes.)
 //|
 //|   *New in CircuitPython 4.0:* ``timeout`` has incompatibly changed units from milliseconds to seconds.
@@ -69,6 +69,12 @@ typedef struct {
 extern const busio_uart_parity_obj_t busio_uart_parity_even_obj;
 extern const busio_uart_parity_obj_t busio_uart_parity_odd_obj;
 
+STATIC void validate_timeout(mp_float_t timeout) {
+    if (timeout < (mp_float_t) 0.0f ||  timeout > (mp_float_t) 100.0f) {
+        mp_raise_ValueError(translate("timeout must be 0.0-100.0 (units are now seconds, not msecs)"));
+    }
+}
+
 STATIC mp_obj_t busio_uart_make_new(const mp_obj_type_t *type, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     // Always initially allocate the UART object within the long-lived heap.
     // This is needed to avoid crashes with certain UART implementations which
@@ -116,9 +122,7 @@ STATIC mp_obj_t busio_uart_make_new(const mp_obj_type_t *type, size_t n_args, co
     }
 
     mp_float_t timeout = mp_obj_get_float(args[ARG_timeout].u_obj);
-    if (timeout > (mp_float_t)100.0) {
-        mp_raise_ValueError(translate("timeout >100 (units are now seconds, not msecs)"));
-    }
+    validate_timeout(timeout);
 
     common_hal_busio_uart_construct(self, tx, rx,
                                     args[ARG_baudrate].u_int, bits, parity, stop, timeout,
@@ -286,6 +290,35 @@ const mp_obj_property_t busio_uart_in_waiting_obj = {
               (mp_obj_t)&mp_const_none_obj},
 };
 
+//|   .. attribute:: timeout
+//|
+//|     The current timeout, in seconds (float).
+//|
+STATIC mp_obj_t busio_uart_obj_get_timeout(mp_obj_t self_in) {
+    busio_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    return mp_obj_new_float(common_hal_busio_uart_get_timeout(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(busio_uart_get_timeout_obj, busio_uart_obj_get_timeout);
+
+STATIC mp_obj_t busio_uart_obj_set_timeout(mp_obj_t self_in, mp_obj_t timeout) {
+    busio_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    mp_float_t timeout_float = mp_obj_get_float(timeout);
+    validate_timeout(timeout_float);
+    common_hal_busio_uart_set_timeout(self, timeout_float);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(busio_uart_set_timeout_obj, busio_uart_obj_set_timeout);
+
+
+const mp_obj_property_t busio_uart_timeout_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&busio_uart_get_timeout_obj,
+              (mp_obj_t)&busio_uart_set_timeout_obj,
+              (mp_obj_t)&mp_const_none_obj},
+};
+
 //|   .. method:: reset_input_buffer()
 //|
 //|     Discard any unread characters in the input buffer.
@@ -355,8 +388,9 @@ STATIC const mp_rom_map_elem_t busio_uart_locals_dict_table[] = {
     { 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) },
+    { 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) },
+    { MP_ROM_QSTR(MP_QSTR_timeout),      MP_ROM_PTR(&busio_uart_timeout_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 776a996be..cfd2c800c 100644
--- a/shared-bindings/busio/UART.h
+++ b/shared-bindings/busio/UART.h
@@ -57,7 +57,8 @@ extern size_t common_hal_busio_uart_write(busio_uart_obj_t *self,
 
 extern uint32_t common_hal_busio_uart_get_baudrate(busio_uart_obj_t *self);
 extern void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrate);
-
+extern mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self);
+extern void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout);
 
 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);
diff --git a/shared-module/board/__init__.c b/shared-module/board/__init__.c
index dd07d7190..914bc4313 100644
--- a/shared-module/board/__init__.c
+++ b/shared-module/board/__init__.c
@@ -101,7 +101,7 @@ mp_obj_t common_hal_board_create_uart(void) {
     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);
+    common_hal_busio_uart_construct(self, tx, rx, 9600, 8, PARITY_NONE, 1, 1.0f, 64);
     MP_STATE_VM(shared_uart_bus) = MP_OBJ_FROM_PTR(self);
     return MP_STATE_VM(shared_uart_bus);
 }