stm32: Split out UART Python bindings from uart.c to machine_uart.c.

5 files changed, 717 insertions, 673 deletions

diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index a5adf03b6..678ece9bd 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -243,6 +243,7 @@ SRC_C = \
 	help.c \
 	machine_i2c.c \
 	machine_spi.c \
+	machine_uart.c \
 	modmachine.c \
 	modpyb.c \
 	modstm.c \
diff --git a/ports/stm32/machine_uart.c b/ports/stm32/machine_uart.c
new file mode 100644
index 000000000..8746d3bbc
--- /dev/null
+++ b/ports/stm32/machine_uart.c
@@ -0,0 +1,596 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2018 Damien P. George
+ *
+ * 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 <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+
+#include "py/runtime.h"
+#include "py/stream.h"
+#include "py/mperrno.h"
+#include "py/mphal.h"
+#include "lib/utils/interrupt_char.h"
+#include "uart.h"
+#include "irq.h"
+#include "pendsv.h"
+
+/// \moduleref pyb
+/// \class UART - duplex serial communication bus
+///
+/// UART implements the standard UART/USART duplex serial communications protocol.  At
+/// the physical level it consists of 2 lines: RX and TX.  The unit of communication
+/// is a character (not to be confused with a string character) which can be 8 or 9
+/// bits wide.
+///
+/// UART objects can be created and initialised using:
+///
+///     from pyb import UART
+///
+///     uart = UART(1, 9600)                         # init with given baudrate
+///     uart.init(9600, bits=8, parity=None, stop=1) # init with given parameters
+///
+/// Bits can be 8 or 9.  Parity can be None, 0 (even) or 1 (odd).  Stop can be 1 or 2.
+///
+/// A UART object acts like a stream object and reading and writing is done
+/// using the standard stream methods:
+///
+///     uart.read(10)       # read 10 characters, returns a bytes object
+///     uart.read()         # read all available characters
+///     uart.readline()     # read a line
+///     uart.readinto(buf)  # read and store into the given buffer
+///     uart.write('abc')   # write the 3 characters
+///
+/// Individual characters can be read/written using:
+///
+///     uart.readchar()     # read 1 character and returns it as an integer
+///     uart.writechar(42)  # write 1 character
+///
+/// To check if there is anything to be read, use:
+///
+///     uart.any()               # returns True if any characters waiting
+
+STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    if (!self->is_enabled) {
+        mp_printf(print, "UART(%u)", self->uart_id);
+    } else {
+        mp_int_t bits;
+        switch (self->uart.Init.WordLength) {
+            #ifdef UART_WORDLENGTH_7B
+            case UART_WORDLENGTH_7B: bits = 7; break;
+            #endif
+            case UART_WORDLENGTH_8B: bits = 8; break;
+            case UART_WORDLENGTH_9B: default: bits = 9; break;
+        }
+        if (self->uart.Init.Parity != UART_PARITY_NONE) {
+            bits -= 1;
+        }
+        mp_printf(print, "UART(%u, baudrate=%u, bits=%u, parity=",
+            self->uart_id, self->uart.Init.BaudRate, bits);
+        if (self->uart.Init.Parity == UART_PARITY_NONE) {
+            mp_print_str(print, "None");
+        } else if (self->uart.Init.Parity == UART_PARITY_EVEN) {
+            mp_print_str(print, "0");
+        } else {
+            mp_print_str(print, "1");
+        }
+        mp_printf(print, ", stop=%u, flow=",
+            self->uart.Init.StopBits == UART_STOPBITS_1 ? 1 : 2);
+        if (self->uart.Init.HwFlowCtl == UART_HWCONTROL_NONE) {
+            mp_print_str(print, "0");
+        } else {
+            if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_RTS) {
+                mp_print_str(print, "RTS");
+                if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
+                   mp_print_str(print, "|");
+                }
+            }
+            if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
+                mp_print_str(print, "CTS");
+            }
+        }
+        mp_printf(print, ", timeout=%u, timeout_char=%u, rxbuf=%u)",
+            self->timeout, self->timeout_char,
+            self->read_buf_len == 0 ? 0 : self->read_buf_len - 1); // -1 to adjust for usable length of buffer
+    }
+}
+
+/// \method init(baudrate, bits=8, parity=None, stop=1, *, timeout=1000, timeout_char=0, flow=0, read_buf_len=64)
+///
+/// Initialise the UART bus with the given parameters:
+///
+///   - `baudrate` is the clock rate.
+///   - `bits` is the number of bits per byte, 7, 8 or 9.
+///   - `parity` is the parity, `None`, 0 (even) or 1 (odd).
+///   - `stop` is the number of stop bits, 1 or 2.
+///   - `timeout` is the timeout in milliseconds to wait for the first character.
+///   - `timeout_char` is the timeout in milliseconds to wait between characters.
+///   - `flow` is RTS | CTS where RTS == 256, CTS == 512
+///   - `read_buf_len` is the character length of the read buffer (0 to disable).
+STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_baudrate, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 9600} },
+        { MP_QSTR_bits, MP_ARG_INT, {.u_int = 8} },
+        { MP_QSTR_parity, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_stop, MP_ARG_INT, {.u_int = 1} },
+        { MP_QSTR_flow, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = UART_HWCONTROL_NONE} },
+        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1000} },
+        { MP_QSTR_timeout_char, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+        { MP_QSTR_rxbuf, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_read_buf_len, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 64} }, // legacy
+    };
+
+    // parse args
+    struct {
+        mp_arg_val_t baudrate, bits, parity, stop, flow, timeout, timeout_char, rxbuf, read_buf_len;
+    } args;
+    mp_arg_parse_all(n_args, pos_args, kw_args,
+        MP_ARRAY_SIZE(allowed_args), allowed_args, (mp_arg_val_t*)&args);
+
+    // set the UART configuration values
+    memset(&self->uart, 0, sizeof(self->uart));
+    UART_InitTypeDef *init = &self->uart.Init;
+
+    // baudrate
+    init->BaudRate = args.baudrate.u_int;
+
+    // parity
+    mp_int_t bits = args.bits.u_int;
+    if (args.parity.u_obj == mp_const_none) {
+        init->Parity = UART_PARITY_NONE;
+    } else {
+        mp_int_t parity = mp_obj_get_int(args.parity.u_obj);
+        init->Parity = (parity & 1) ? UART_PARITY_ODD : UART_PARITY_EVEN;
+        bits += 1; // STs convention has bits including parity
+    }
+
+    // number of bits
+    if (bits == 8) {
+        init->WordLength = UART_WORDLENGTH_8B;
+    } else if (bits == 9) {
+        init->WordLength = UART_WORDLENGTH_9B;
+    #ifdef UART_WORDLENGTH_7B
+    } else if (bits == 7) {
+        init->WordLength = UART_WORDLENGTH_7B;
+    #endif
+    } else {
+        mp_raise_ValueError("unsupported combination of bits and parity");
+    }
+
+    // stop bits
+    switch (args.stop.u_int) {
+        case 1: init->StopBits = UART_STOPBITS_1; break;
+        default: init->StopBits = UART_STOPBITS_2; break;
+    }
+
+    // flow control
+    init->HwFlowCtl = args.flow.u_int;
+
+    // extra config (not yet configurable)
+    init->Mode = UART_MODE_TX_RX;
+    init->OverSampling = UART_OVERSAMPLING_16;
+
+    // init UART (if it fails, it's because the port doesn't exist)
+    if (!uart_init2(self)) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "UART(%d) doesn't exist", self->uart_id));
+    }
+
+    // set timeout
+    self->timeout = args.timeout.u_int;
+
+    // set timeout_char
+    // make sure it is at least as long as a whole character (13 bits to be safe)
+    // minimum value is 2ms because sys-tick has a resolution of only 1ms
+    self->timeout_char = args.timeout_char.u_int;
+    uint32_t min_timeout_char = 13000 / init->BaudRate + 2;
+    if (self->timeout_char < min_timeout_char) {
+        self->timeout_char = min_timeout_char;
+    }
+
+    // setup the read buffer
+    m_del(byte, self->read_buf, self->read_buf_len << self->char_width);
+    if (init->WordLength == UART_WORDLENGTH_9B && init->Parity == UART_PARITY_NONE) {
+        self->char_mask = 0x1ff;
+        self->char_width = CHAR_WIDTH_9BIT;
+    } else {
+        if (init->WordLength == UART_WORDLENGTH_9B || init->Parity == UART_PARITY_NONE) {
+            self->char_mask = 0xff;
+        } else {
+            self->char_mask = 0x7f;
+        }
+        self->char_width = CHAR_WIDTH_8BIT;
+    }
+    self->read_buf_head = 0;
+    self->read_buf_tail = 0;
+    if (args.rxbuf.u_int >= 0) {
+        // rxbuf overrides legacy read_buf_len
+        args.read_buf_len.u_int = args.rxbuf.u_int;
+    }
+    if (args.read_buf_len.u_int <= 0) {
+        // no read buffer
+        self->read_buf_len = 0;
+        self->read_buf = NULL;
+        HAL_NVIC_DisableIRQ(self->irqn);
+        __HAL_UART_DISABLE_IT(&self->uart, UART_IT_RXNE);
+    } else {
+        // read buffer using interrupts
+        self->read_buf_len = args.read_buf_len.u_int + 1; // +1 to adjust for usable length of buffer
+        self->read_buf = m_new(byte, self->read_buf_len << self->char_width);
+        __HAL_UART_ENABLE_IT(&self->uart, UART_IT_RXNE);
+        NVIC_SetPriority(IRQn_NONNEG(self->irqn), IRQ_PRI_UART);
+        HAL_NVIC_EnableIRQ(self->irqn);
+    }
+
+    // compute actual baudrate that was configured
+    // (this formula assumes UART_OVERSAMPLING_16)
+    uint32_t actual_baudrate = 0;
+    #if defined(STM32F0)
+    actual_baudrate = HAL_RCC_GetPCLK1Freq();
+    #elif defined(STM32F7) || defined(STM32H7)
+    UART_ClockSourceTypeDef clocksource = UART_CLOCKSOURCE_UNDEFINED;
+    UART_GETCLOCKSOURCE(&self->uart, clocksource);
+    switch (clocksource) {
+        #if defined(STM32H7)
+        case UART_CLOCKSOURCE_D2PCLK1: actual_baudrate = HAL_RCC_GetPCLK1Freq(); break;
+        case UART_CLOCKSOURCE_D3PCLK1: actual_baudrate = HAL_RCC_GetPCLK1Freq(); break;
+        case UART_CLOCKSOURCE_D2PCLK2: actual_baudrate = HAL_RCC_GetPCLK2Freq(); break;
+        #else
+        case UART_CLOCKSOURCE_PCLK1:  actual_baudrate = HAL_RCC_GetPCLK1Freq(); break;
+        case UART_CLOCKSOURCE_PCLK2:  actual_baudrate = HAL_RCC_GetPCLK2Freq(); break;
+        case UART_CLOCKSOURCE_SYSCLK: actual_baudrate = HAL_RCC_GetSysClockFreq(); break;
+        #endif
+        #if defined(STM32H7)
+        case UART_CLOCKSOURCE_CSI:    actual_baudrate = CSI_VALUE; break;
+        #endif
+        case UART_CLOCKSOURCE_HSI:    actual_baudrate = HSI_VALUE; break;
+        case UART_CLOCKSOURCE_LSE:    actual_baudrate = LSE_VALUE; break;
+        #if defined(STM32H7)
+        case UART_CLOCKSOURCE_PLL2:
+        case UART_CLOCKSOURCE_PLL3:
+        #endif
+        case UART_CLOCKSOURCE_UNDEFINED: break;
+    }
+    #else
+    if (self->uart.Instance == USART1
+        #if defined(USART6)
+        || self->uart.Instance == USART6
+        #endif
+        ) {
+        actual_baudrate = HAL_RCC_GetPCLK2Freq();
+    } else {
+        actual_baudrate = HAL_RCC_GetPCLK1Freq();
+    }
+    #endif
+    actual_baudrate /= self->uart.Instance->BRR;
+
+    // check we could set the baudrate within 5%
+    uint32_t baudrate_diff;
+    if (actual_baudrate > init->BaudRate) {
+        baudrate_diff = actual_baudrate - init->BaudRate;
+    } else {
+        baudrate_diff = init->BaudRate - actual_baudrate;
+    }
+    init->BaudRate = actual_baudrate; // remember actual baudrate for printing
+    if (20 * baudrate_diff > init->BaudRate) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "set baudrate %d is not within 5%% of desired value", actual_baudrate));
+    }
+
+    return mp_const_none;
+}
+
+/// \classmethod \constructor(bus, ...)
+///
+/// Construct a UART object on the given bus.  `bus` can be 1-6, or 'XA', 'XB', 'YA', or 'YB'.
+/// With no additional parameters, the UART object is created but not
+/// initialised (it has the settings from the last initialisation of
+/// the bus, if any).  If extra arguments are given, the bus is initialised.
+/// See `init` for parameters of initialisation.
+///
+/// The physical pins of the UART busses are:
+///
+///   - `UART(4)` is on `XA`: `(TX, RX) = (X1, X2) = (PA0, PA1)`
+///   - `UART(1)` is on `XB`: `(TX, RX) = (X9, X10) = (PB6, PB7)`
+///   - `UART(6)` is on `YA`: `(TX, RX) = (Y1, Y2) = (PC6, PC7)`
+///   - `UART(3)` is on `YB`: `(TX, RX) = (Y9, Y10) = (PB10, PB11)`
+///   - `UART(2)` is on: `(TX, RX) = (X3, X4) = (PA2, PA3)`
+STATIC mp_obj_t pyb_uart_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    // check arguments
+    mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);
+
+    // work out port
+    int uart_id = 0;
+    if (MP_OBJ_IS_STR(args[0])) {
+        const char *port = mp_obj_str_get_str(args[0]);
+        if (0) {
+        #ifdef MICROPY_HW_UART1_NAME
+        } else if (strcmp(port, MICROPY_HW_UART1_NAME) == 0) {
+            uart_id = PYB_UART_1;
+        #endif
+        #ifdef MICROPY_HW_UART2_NAME
+        } else if (strcmp(port, MICROPY_HW_UART2_NAME) == 0) {
+            uart_id = PYB_UART_2;
+        #endif
+        #ifdef MICROPY_HW_UART3_NAME
+        } else if (strcmp(port, MICROPY_HW_UART3_NAME) == 0) {
+            uart_id = PYB_UART_3;
+        #endif
+        #ifdef MICROPY_HW_UART4_NAME
+        } else if (strcmp(port, MICROPY_HW_UART4_NAME) == 0) {
+            uart_id = PYB_UART_4;
+        #endif
+        #ifdef MICROPY_HW_UART5_NAME
+        } else if (strcmp(port, MICROPY_HW_UART5_NAME) == 0) {
+            uart_id = PYB_UART_5;
+        #endif
+        #ifdef MICROPY_HW_UART6_NAME
+        } else if (strcmp(port, MICROPY_HW_UART6_NAME) == 0) {
+            uart_id = PYB_UART_6;
+        #endif
+        #ifdef MICROPY_HW_UART7_NAME
+        } else if (strcmp(port, MICROPY_HW_UART7_NAME) == 0) {
+            uart_id = PYB_UART_7;
+        #endif
+        #ifdef MICROPY_HW_UART8_NAME
+        } else if (strcmp(port, MICROPY_HW_UART8_NAME) == 0) {
+            uart_id = PYB_UART_8;
+        #endif
+        } else {
+            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "UART(%s) doesn't exist", port));
+        }
+    } else {
+        uart_id = mp_obj_get_int(args[0]);
+        if (!uart_exists(uart_id)) {
+            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "UART(%d) doesn't exist", uart_id));
+        }
+    }
+
+    pyb_uart_obj_t *self;
+    if (MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1] == NULL) {
+        // create new UART object
+        self = m_new0(pyb_uart_obj_t, 1);
+        self->base.type = &pyb_uart_type;
+        self->uart_id = uart_id;
+        MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1] = self;
+    } else {
+        // reference existing UART object
+        self = MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1];
+    }
+
+    if (n_args > 1 || n_kw > 0) {
+        // start the peripheral
+        mp_map_t kw_args;
+        mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
+        pyb_uart_init_helper(self, n_args - 1, args + 1, &kw_args);
+    }
+
+    return MP_OBJ_FROM_PTR(self);
+}
+
+STATIC mp_obj_t pyb_uart_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
+    return pyb_uart_init_helper(MP_OBJ_TO_PTR(args[0]), n_args - 1, args + 1, kw_args);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_uart_init_obj, 1, pyb_uart_init);
+
+/// \method deinit()
+/// Turn off the UART bus.
+STATIC mp_obj_t pyb_uart_deinit(mp_obj_t self_in) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    uart_deinit(self);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_deinit_obj, pyb_uart_deinit);
+
+/// \method any()
+/// Return `True` if any characters waiting, else `False`.
+STATIC mp_obj_t pyb_uart_any(mp_obj_t self_in) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return MP_OBJ_NEW_SMALL_INT(uart_rx_any(self));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_any_obj, pyb_uart_any);
+
+/// \method writechar(char)
+/// Write a single character on the bus.  `char` is an integer to write.
+/// Return value: `None`.
+STATIC mp_obj_t pyb_uart_writechar(mp_obj_t self_in, mp_obj_t char_in) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    // get the character to write (might be 9 bits)
+    uint16_t data = mp_obj_get_int(char_in);
+
+    // write the character
+    int errcode;
+    if (uart_tx_wait(self, self->timeout)) {
+        uart_tx_data(self, &data, 1, &errcode);
+    } else {
+        errcode = MP_ETIMEDOUT;
+    }
+
+    if (errcode != 0) {
+        mp_raise_OSError(errcode);
+    }
+
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_uart_writechar_obj, pyb_uart_writechar);
+
+/// \method readchar()
+/// Receive a single character on the bus.
+/// Return value: The character read, as an integer.  Returns -1 on timeout.
+STATIC mp_obj_t pyb_uart_readchar(mp_obj_t self_in) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    if (uart_rx_wait(self, self->timeout)) {
+        return MP_OBJ_NEW_SMALL_INT(uart_rx_char(self));
+    } else {
+        // return -1 on timeout
+        return MP_OBJ_NEW_SMALL_INT(-1);
+    }
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_readchar_obj, pyb_uart_readchar);
+
+// uart.sendbreak()
+STATIC mp_obj_t pyb_uart_sendbreak(mp_obj_t self_in) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    #if defined(STM32F0) || defined(STM32F7) || defined(STM32L4) || defined(STM32H7)
+    self->uart.Instance->RQR = USART_RQR_SBKRQ; // write-only register
+    #else
+    self->uart.Instance->CR1 |= USART_CR1_SBK;
+    #endif
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_sendbreak_obj, pyb_uart_sendbreak);
+
+STATIC const mp_rom_map_elem_t pyb_uart_locals_dict_table[] = {
+    // instance methods
+
+    { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&pyb_uart_init_obj) },
+    { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&pyb_uart_deinit_obj) },
+    { MP_ROM_QSTR(MP_QSTR_any), MP_ROM_PTR(&pyb_uart_any_obj) },
+
+    /// \method read([nbytes])
+    { MP_ROM_QSTR(MP_QSTR_read), MP_ROM_PTR(&mp_stream_read_obj) },
+    /// \method readline()
+    { MP_ROM_QSTR(MP_QSTR_readline), MP_ROM_PTR(&mp_stream_unbuffered_readline_obj)},
+    /// \method readinto(buf[, nbytes])
+    { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&mp_stream_readinto_obj) },
+    /// \method write(buf)
+    { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&mp_stream_write_obj) },
+
+    { MP_ROM_QSTR(MP_QSTR_writechar), MP_ROM_PTR(&pyb_uart_writechar_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readchar), MP_ROM_PTR(&pyb_uart_readchar_obj) },
+    { MP_ROM_QSTR(MP_QSTR_sendbreak), MP_ROM_PTR(&pyb_uart_sendbreak_obj) },
+
+    // class constants
+    { MP_ROM_QSTR(MP_QSTR_RTS), MP_ROM_INT(UART_HWCONTROL_RTS) },
+    { MP_ROM_QSTR(MP_QSTR_CTS), MP_ROM_INT(UART_HWCONTROL_CTS) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(pyb_uart_locals_dict, pyb_uart_locals_dict_table);
+
+STATIC mp_uint_t pyb_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, int *errcode) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    byte *buf = buf_in;
+
+    // check that size is a multiple of character width
+    if (size & self->char_width) {
+        *errcode = MP_EIO;
+        return MP_STREAM_ERROR;
+    }
+
+    // convert byte size to char size
+    size >>= self->char_width;
+
+    // make sure we want at least 1 char
+    if (size == 0) {
+        return 0;
+    }
+
+    // wait for first char to become available
+    if (!uart_rx_wait(self, self->timeout)) {
+        // return EAGAIN error to indicate non-blocking (then read() method returns None)
+        *errcode = MP_EAGAIN;
+        return MP_STREAM_ERROR;
+    }
+
+    // read the data
+    byte *orig_buf = buf;
+    for (;;) {
+        int data = uart_rx_char(self);
+        if (self->char_width == CHAR_WIDTH_9BIT) {
+            *(uint16_t*)buf = data;
+            buf += 2;
+        } else {
+            *buf++ = data;
+        }
+        if (--size == 0 || !uart_rx_wait(self, self->timeout_char)) {
+            // return number of bytes read
+            return buf - orig_buf;
+        }
+    }
+}
+
+STATIC mp_uint_t pyb_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t size, int *errcode) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    const byte *buf = buf_in;
+
+    // check that size is a multiple of character width
+    if (size & self->char_width) {
+        *errcode = MP_EIO;
+        return MP_STREAM_ERROR;
+    }
+
+    // wait to be able to write the first character. EAGAIN causes write to return None
+    if (!uart_tx_wait(self, self->timeout)) {
+        *errcode = MP_EAGAIN;
+        return MP_STREAM_ERROR;
+    }
+
+    // write the data
+    size_t num_tx = uart_tx_data(self, buf, size >> self->char_width, errcode);
+
+    if (*errcode == 0 || *errcode == MP_ETIMEDOUT) {
+        // return number of bytes written, even if there was a timeout
+        return num_tx << self->char_width;
+    } else {
+        return MP_STREAM_ERROR;
+    }
+}
+
+STATIC mp_uint_t pyb_uart_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr_t arg, int *errcode) {
+    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_uint_t ret;
+    if (request == MP_STREAM_POLL) {
+        uintptr_t flags = arg;
+        ret = 0;
+        if ((flags & MP_STREAM_POLL_RD) && uart_rx_any(self)) {
+            ret |= MP_STREAM_POLL_RD;
+        }
+        if ((flags & MP_STREAM_POLL_WR) && __HAL_UART_GET_FLAG(&self->uart, UART_FLAG_TXE)) {
+            ret |= MP_STREAM_POLL_WR;
+        }
+    } else {
+        *errcode = MP_EINVAL;
+        ret = MP_STREAM_ERROR;
+    }
+    return ret;
+}
+
+STATIC const mp_stream_p_t uart_stream_p = {
+    .read = pyb_uart_read,
+    .write = pyb_uart_write,
+    .ioctl = pyb_uart_ioctl,
+    .is_text = false,
+};
+
+const mp_obj_type_t pyb_uart_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_UART,
+    .print = pyb_uart_print,
+    .make_new = pyb_uart_make_new,
+    .getiter = mp_identity_getiter,
+    .iternext = mp_stream_unbuffered_iter,
+    .protocol = &uart_stream_p,
+    .locals_dict = (mp_obj_dict_t*)&pyb_uart_locals_dict,
+};
diff --git a/ports/stm32/main.c b/ports/stm32/main.c
index 6c37e1351..f14176efa 100644
--- a/ports/stm32/main.c
+++ b/ports/stm32/main.c
@@ -755,7 +755,7 @@ soft_reset_exit:
     mod_network_deinit();
     #endif
     timer_deinit();
-    uart_deinit();
+    uart_deinit_all();
     #if MICROPY_HW_ENABLE_CAN
     can_deinit();
     #endif
diff --git a/ports/stm32/uart.c b/ports/stm32/uart.c
index 78d853d03..83eef705a 100644
--- a/ports/stm32/uart.c
+++ b/ports/stm32/uart.c
@@ -37,62 +37,6 @@
 #include "irq.h"
 #include "pendsv.h"
 
-/// \moduleref pyb
-/// \class UART - duplex serial communication bus
-///
-/// UART implements the standard UART/USART duplex serial communications protocol.  At
-/// the physical level it consists of 2 lines: RX and TX.  The unit of communication
-/// is a character (not to be confused with a string character) which can be 8 or 9
-/// bits wide.
-///
-/// UART objects can be created and initialised using:
-///
-///     from pyb import UART
-///
-///     uart = UART(1, 9600)                         # init with given baudrate
-///     uart.init(9600, bits=8, parity=None, stop=1) # init with given parameters
-///
-/// Bits can be 8 or 9.  Parity can be None, 0 (even) or 1 (odd).  Stop can be 1 or 2.
-///
-/// A UART object acts like a stream object and reading and writing is done
-/// using the standard stream methods:
-///
-///     uart.read(10)       # read 10 characters, returns a bytes object
-///     uart.read()         # read all available characters
-///     uart.readline()     # read a line
-///     uart.readinto(buf)  # read and store into the given buffer
-///     uart.write('abc')   # write the 3 characters
-///
-/// Individual characters can be read/written using:
-///
-///     uart.readchar()     # read 1 character and returns it as an integer
-///     uart.writechar(42)  # write 1 character
-///
-/// To check if there is anything to be read, use:
-///
-///     uart.any()               # returns True if any characters waiting
-
-#define CHAR_WIDTH_8BIT (0)
-#define CHAR_WIDTH_9BIT (1)
-
-struct _pyb_uart_obj_t {
-    mp_obj_base_t base;
-    UART_HandleTypeDef uart;            // this is 17 words big
-    IRQn_Type irqn;
-    pyb_uart_t uart_id : 8;
-    bool is_enabled : 1;
-    bool attached_to_repl;              // whether the UART is attached to REPL
-    byte char_width;                    // 0 for 7,8 bit chars, 1 for 9 bit chars
-    uint16_t char_mask;                 // 0x7f for 7 bit, 0xff for 8 bit, 0x1ff for 9 bit
-    uint16_t timeout;                   // timeout waiting for first char
-    uint16_t timeout_char;              // timeout waiting between chars
-    uint16_t read_buf_len;              // len in chars; buf can hold len-1 chars
-    volatile uint16_t read_buf_head;    // indexes first empty slot
-    uint16_t read_buf_tail;             // indexes first full slot (not full if equals head)
-    byte *read_buf;                     // byte or uint16_t, depending on char size
-};
-
-STATIC mp_obj_t pyb_uart_deinit(mp_obj_t self_in);
 extern void NORETURN __fatal_error(const char *msg);
 
 void uart_init0(void) {
@@ -119,16 +63,16 @@ void uart_init0(void) {
 }
 
 // unregister all interrupt sources
-void uart_deinit(void) {
+void uart_deinit_all(void) {
     for (int i = 0; i < MP_ARRAY_SIZE(MP_STATE_PORT(pyb_uart_obj_all)); i++) {
         pyb_uart_obj_t *uart_obj = MP_STATE_PORT(pyb_uart_obj_all)[i];
         if (uart_obj != NULL) {
-            pyb_uart_deinit(MP_OBJ_FROM_PTR(uart_obj));
+            uart_deinit(uart_obj);
         }
     }
 }
 
-STATIC bool uart_exists(int uart_id) {
+bool uart_exists(int uart_id) {
     if (uart_id > MP_ARRAY_SIZE(MP_STATE_PORT(pyb_uart_obj_all))) {
         // safeguard against pyb_uart_obj_all array being configured too small
         return false;
@@ -171,7 +115,7 @@ STATIC bool uart_exists(int uart_id) {
 }
 
 // assumes Init parameters have been set up correctly
-STATIC bool uart_init2(pyb_uart_obj_t *uart_obj) {
+bool uart_init2(pyb_uart_obj_t *uart_obj) {
     USART_TypeDef *UARTx;
     IRQn_Type irqn;
     int uart_unit;
@@ -358,6 +302,91 @@ STATIC bool uart_init2(pyb_uart_obj_t *uart_obj) {
     return true;
 }
 
+void uart_deinit(pyb_uart_obj_t *self) {
+    self->is_enabled = false;
+    UART_HandleTypeDef *uart = &self->uart;
+    HAL_UART_DeInit(uart);
+    if (uart->Instance == USART1) {
+        HAL_NVIC_DisableIRQ(USART1_IRQn);
+        __HAL_RCC_USART1_FORCE_RESET();
+        __HAL_RCC_USART1_RELEASE_RESET();
+        __HAL_RCC_USART1_CLK_DISABLE();
+    } else if (uart->Instance == USART2) {
+        HAL_NVIC_DisableIRQ(USART2_IRQn);
+        __HAL_RCC_USART2_FORCE_RESET();
+        __HAL_RCC_USART2_RELEASE_RESET();
+        __HAL_RCC_USART2_CLK_DISABLE();
+    #if defined(USART3)
+    } else if (uart->Instance == USART3) {
+        #if !defined(STM32F0)
+        HAL_NVIC_DisableIRQ(USART3_IRQn);
+        #endif
+        __HAL_RCC_USART3_FORCE_RESET();
+        __HAL_RCC_USART3_RELEASE_RESET();
+        __HAL_RCC_USART3_CLK_DISABLE();
+    #endif
+    #if defined(UART4)
+    } else if (uart->Instance == UART4) {
+        HAL_NVIC_DisableIRQ(UART4_IRQn);
+        __HAL_RCC_UART4_FORCE_RESET();
+        __HAL_RCC_UART4_RELEASE_RESET();
+        __HAL_RCC_UART4_CLK_DISABLE();
+    #endif
+    #if defined(USART4)
+    } else if (uart->Instance == USART4) {
+        __HAL_RCC_USART4_FORCE_RESET();
+        __HAL_RCC_USART4_RELEASE_RESET();
+        __HAL_RCC_USART4_CLK_DISABLE();
+    #endif
+    #if defined(UART5)
+    } else if (uart->Instance == UART5) {
+        HAL_NVIC_DisableIRQ(UART5_IRQn);
+        __HAL_RCC_UART5_FORCE_RESET();
+        __HAL_RCC_UART5_RELEASE_RESET();
+        __HAL_RCC_UART5_CLK_DISABLE();
+    #endif
+    #if defined(USART5)
+    } else if (uart->Instance == USART5) {
+        __HAL_RCC_USART5_FORCE_RESET();
+        __HAL_RCC_USART5_RELEASE_RESET();
+        __HAL_RCC_USART5_CLK_DISABLE();
+    #endif
+    #if defined(UART6)
+    } else if (uart->Instance == USART6) {
+        HAL_NVIC_DisableIRQ(USART6_IRQn);
+        __HAL_RCC_USART6_FORCE_RESET();
+        __HAL_RCC_USART6_RELEASE_RESET();
+        __HAL_RCC_USART6_CLK_DISABLE();
+    #endif
+    #if defined(UART7)
+    } else if (uart->Instance == UART7) {
+        HAL_NVIC_DisableIRQ(UART7_IRQn);
+        __HAL_RCC_UART7_FORCE_RESET();
+        __HAL_RCC_UART7_RELEASE_RESET();
+        __HAL_RCC_UART7_CLK_DISABLE();
+    #endif
+    #if defined(USART7)
+    } else if (uart->Instance == USART7) {
+        __HAL_RCC_USART7_FORCE_RESET();
+        __HAL_RCC_USART7_RELEASE_RESET();
+        __HAL_RCC_USART7_CLK_DISABLE();
+    #endif
+    #if defined(UART8)
+    } else if (uart->Instance == UART8) {
+        HAL_NVIC_DisableIRQ(UART8_IRQn);
+        __HAL_RCC_UART8_FORCE_RESET();
+        __HAL_RCC_UART8_RELEASE_RESET();
+        __HAL_RCC_UART8_CLK_DISABLE();
+    #endif
+    #if defined(USART8)
+    } else if (uart->Instance == USART8) {
+        __HAL_RCC_USART8_FORCE_RESET();
+        __HAL_RCC_USART8_RELEASE_RESET();
+        __HAL_RCC_USART8_CLK_DISABLE();
+    #endif
+    }
+}
+
 void uart_attach_to_repl(pyb_uart_obj_t *self, bool attached) {
     self->attached_to_repl = attached;
 }
@@ -391,7 +420,7 @@ mp_uint_t uart_rx_any(pyb_uart_obj_t *self) {
 // Waits at most timeout milliseconds for at least 1 char to become ready for
 // reading (from buf or for direct reading).
 // Returns true if something available, false if not.
-STATIC bool uart_rx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
+bool uart_rx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
     uint32_t start = HAL_GetTick();
     for (;;) {
         if (self->read_buf_tail != self->read_buf_head || __HAL_UART_GET_FLAG(&self->uart, UART_FLAG_RXNE) != RESET) {
@@ -432,7 +461,7 @@ int uart_rx_char(pyb_uart_obj_t *self) {
 
 // Waits at most timeout milliseconds for TX register to become empty.
 // Returns true if can write, false if can't.
-STATIC bool uart_tx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
+bool uart_tx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
     uint32_t start = HAL_GetTick();
     for (;;) {
         if (__HAL_UART_GET_FLAG(&self->uart, UART_FLAG_TXE)) {
@@ -465,7 +494,7 @@ STATIC bool uart_wait_flag_set(pyb_uart_obj_t *self, uint32_t flag, uint32_t tim
 // num_chars - number of characters to send (9-bit chars count for 2 bytes from src)
 // *errcode - returns 0 for success, MP_Exxx on error
 // returns the number of characters sent (valid even if there was an error)
-STATIC size_t uart_tx_data(pyb_uart_obj_t *self, const void *src_in, size_t num_chars, int *errcode) {
+size_t uart_tx_data(pyb_uart_obj_t *self, const void *src_in, size_t num_chars, int *errcode) {
     if (num_chars == 0) {
         *errcode = 0;
         return 0;
@@ -563,610 +592,3 @@ void uart_irq_handler(mp_uint_t uart_id) {
         }
     }
 }
-
-/******************************************************************************/
-/* MicroPython bindings                                                       */
-
-STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    if (!self->is_enabled) {
-        mp_printf(print, "UART(%u)", self->uart_id);
-    } else {
-        mp_int_t bits;
-        switch (self->uart.Init.WordLength) {
-            #ifdef UART_WORDLENGTH_7B
-            case UART_WORDLENGTH_7B: bits = 7; break;
-            #endif
-            case UART_WORDLENGTH_8B: bits = 8; break;
-            case UART_WORDLENGTH_9B: default: bits = 9; break;
-        }
-        if (self->uart.Init.Parity != UART_PARITY_NONE) {
-            bits -= 1;
-        }
-        mp_printf(print, "UART(%u, baudrate=%u, bits=%u, parity=",
-            self->uart_id, self->uart.Init.BaudRate, bits);
-        if (self->uart.Init.Parity == UART_PARITY_NONE) {
-            mp_print_str(print, "None");
-        } else if (self->uart.Init.Parity == UART_PARITY_EVEN) {
-            mp_print_str(print, "0");
-        } else {
-            mp_print_str(print, "1");
-        }
-        mp_printf(print, ", stop=%u, flow=",
-            self->uart.Init.StopBits == UART_STOPBITS_1 ? 1 : 2);
-        if (self->uart.Init.HwFlowCtl == UART_HWCONTROL_NONE) {
-            mp_print_str(print, "0");
-        } else {
-            if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_RTS) {
-                mp_print_str(print, "RTS");
-                if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
-                   mp_print_str(print, "|");
-                }
-            }
-            if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
-                mp_print_str(print, "CTS");
-            }
-        }
-        mp_printf(print, ", timeout=%u, timeout_char=%u, rxbuf=%u)",
-            self->timeout, self->timeout_char,
-            self->read_buf_len == 0 ? 0 : self->read_buf_len - 1); // -1 to adjust for usable length of buffer
-    }
-}
-
-/// \method init(baudrate, bits=8, parity=None, stop=1, *, timeout=1000, timeout_char=0, flow=0, read_buf_len=64)
-///
-/// Initialise the UART bus with the given parameters:
-///
-///   - `baudrate` is the clock rate.
-///   - `bits` is the number of bits per byte, 7, 8 or 9.
-///   - `parity` is the parity, `None`, 0 (even) or 1 (odd).
-///   - `stop` is the number of stop bits, 1 or 2.
-///   - `timeout` is the timeout in milliseconds to wait for the first character.
-///   - `timeout_char` is the timeout in milliseconds to wait between characters.
-///   - `flow` is RTS | CTS where RTS == 256, CTS == 512
-///   - `read_buf_len` is the character length of the read buffer (0 to disable).
-STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_baudrate, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 9600} },
-        { MP_QSTR_bits, MP_ARG_INT, {.u_int = 8} },
-        { MP_QSTR_parity, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_stop, MP_ARG_INT, {.u_int = 1} },
-        { MP_QSTR_flow, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = UART_HWCONTROL_NONE} },
-        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1000} },
-        { MP_QSTR_timeout_char, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
-        { MP_QSTR_rxbuf, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
-        { MP_QSTR_read_buf_len, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 64} }, // legacy
-    };
-
-    // parse args
-    struct {
-        mp_arg_val_t baudrate, bits, parity, stop, flow, timeout, timeout_char, rxbuf, read_buf_len;
-    } args;
-    mp_arg_parse_all(n_args, pos_args, kw_args,
-        MP_ARRAY_SIZE(allowed_args), allowed_args, (mp_arg_val_t*)&args);
-
-    // set the UART configuration values
-    memset(&self->uart, 0, sizeof(self->uart));
-    UART_InitTypeDef *init = &self->uart.Init;
-
-    // baudrate
-    init->BaudRate = args.baudrate.u_int;
-
-    // parity
-    mp_int_t bits = args.bits.u_int;
-    if (args.parity.u_obj == mp_const_none) {
-        init->Parity = UART_PARITY_NONE;
-    } else {
-        mp_int_t parity = mp_obj_get_int(args.parity.u_obj);
-        init->Parity = (parity & 1) ? UART_PARITY_ODD : UART_PARITY_EVEN;
-        bits += 1; // STs convention has bits including parity
-    }
-
-    // number of bits
-    if (bits == 8) {
-        init->WordLength = UART_WORDLENGTH_8B;
-    } else if (bits == 9) {
-        init->WordLength = UART_WORDLENGTH_9B;
-    #ifdef UART_WORDLENGTH_7B
-    } else if (bits == 7) {
-        init->WordLength = UART_WORDLENGTH_7B;
-    #endif
-    } else {
-        mp_raise_ValueError("unsupported combination of bits and parity");
-    }
-
-    // stop bits
-    switch (args.stop.u_int) {
-        case 1: init->StopBits = UART_STOPBITS_1; break;
-        default: init->StopBits = UART_STOPBITS_2; break;
-    }
-
-    // flow control
-    init->HwFlowCtl = args.flow.u_int;
-
-    // extra config (not yet configurable)
-    init->Mode = UART_MODE_TX_RX;
-    init->OverSampling = UART_OVERSAMPLING_16;
-
-    // init UART (if it fails, it's because the port doesn't exist)
-    if (!uart_init2(self)) {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "UART(%d) doesn't exist", self->uart_id));
-    }
-
-    // set timeout
-    self->timeout = args.timeout.u_int;
-
-    // set timeout_char
-    // make sure it is at least as long as a whole character (13 bits to be safe)
-    // minimum value is 2ms because sys-tick has a resolution of only 1ms
-    self->timeout_char = args.timeout_char.u_int;
-    uint32_t min_timeout_char = 13000 / init->BaudRate + 2;
-    if (self->timeout_char < min_timeout_char) {
-        self->timeout_char = min_timeout_char;
-    }
-
-    // setup the read buffer
-    m_del(byte, self->read_buf, self->read_buf_len << self->char_width);
-    if (init->WordLength == UART_WORDLENGTH_9B && init->Parity == UART_PARITY_NONE) {
-        self->char_mask = 0x1ff;
-        self->char_width = CHAR_WIDTH_9BIT;
-    } else {
-        if (init->WordLength == UART_WORDLENGTH_9B || init->Parity == UART_PARITY_NONE) {
-            self->char_mask = 0xff;
-        } else {
-            self->char_mask = 0x7f;
-        }
-        self->char_width = CHAR_WIDTH_8BIT;
-    }
-    self->read_buf_head = 0;
-    self->read_buf_tail = 0;
-    if (args.rxbuf.u_int >= 0) {
-        // rxbuf overrides legacy read_buf_len
-        args.read_buf_len.u_int = args.rxbuf.u_int;
-    }
-    if (args.read_buf_len.u_int <= 0) {
-        // no read buffer
-        self->read_buf_len = 0;
-        self->read_buf = NULL;
-        HAL_NVIC_DisableIRQ(self->irqn);
-        __HAL_UART_DISABLE_IT(&self->uart, UART_IT_RXNE);
-    } else {
-        // read buffer using interrupts
-        self->read_buf_len = args.read_buf_len.u_int + 1; // +1 to adjust for usable length of buffer
-        self->read_buf = m_new(byte, self->read_buf_len << self->char_width);
-        __HAL_UART_ENABLE_IT(&self->uart, UART_IT_RXNE);
-        NVIC_SetPriority(IRQn_NONNEG(self->irqn), IRQ_PRI_UART);
-        HAL_NVIC_EnableIRQ(self->irqn);
-    }
-
-    // compute actual baudrate that was configured
-    // (this formula assumes UART_OVERSAMPLING_16)
-    uint32_t actual_baudrate = 0;
-    #if defined(STM32F0)
-    actual_baudrate = HAL_RCC_GetPCLK1Freq();
-    #elif defined(STM32F7) || defined(STM32H7)
-    UART_ClockSourceTypeDef clocksource = UART_CLOCKSOURCE_UNDEFINED;
-    UART_GETCLOCKSOURCE(&self->uart, clocksource);
-    switch (clocksource) {
-        #if defined(STM32H7)
-        case UART_CLOCKSOURCE_D2PCLK1: actual_baudrate = HAL_RCC_GetPCLK1Freq(); break;
-        case UART_CLOCKSOURCE_D3PCLK1: actual_baudrate = HAL_RCC_GetPCLK1Freq(); break;
-        case UART_CLOCKSOURCE_D2PCLK2: actual_baudrate = HAL_RCC_GetPCLK2Freq(); break;
-        #else
-        case UART_CLOCKSOURCE_PCLK1:  actual_baudrate = HAL_RCC_GetPCLK1Freq(); break;
-        case UART_CLOCKSOURCE_PCLK2:  actual_baudrate = HAL_RCC_GetPCLK2Freq(); break;
-        case UART_CLOCKSOURCE_SYSCLK: actual_baudrate = HAL_RCC_GetSysClockFreq(); break;
-        #endif
-        #if defined(STM32H7)
-        case UART_CLOCKSOURCE_CSI:    actual_baudrate = CSI_VALUE; break;
-        #endif
-        case UART_CLOCKSOURCE_HSI:    actual_baudrate = HSI_VALUE; break;
-        case UART_CLOCKSOURCE_LSE:    actual_baudrate = LSE_VALUE; break;
-        #if defined(STM32H7)
-        case UART_CLOCKSOURCE_PLL2:
-        case UART_CLOCKSOURCE_PLL3:
-        #endif
-        case UART_CLOCKSOURCE_UNDEFINED: break;
-    }
-    #else
-    if (self->uart.Instance == USART1
-        #if defined(USART6)
-        || self->uart.Instance == USART6
-        #endif
-        ) {
-        actual_baudrate = HAL_RCC_GetPCLK2Freq();
-    } else {
-        actual_baudrate = HAL_RCC_GetPCLK1Freq();
-    }
-    #endif
-    actual_baudrate /= self->uart.Instance->BRR;
-
-    // check we could set the baudrate within 5%
-    uint32_t baudrate_diff;
-    if (actual_baudrate > init->BaudRate) {
-        baudrate_diff = actual_baudrate - init->BaudRate;
-    } else {
-        baudrate_diff = init->BaudRate - actual_baudrate;
-    }
-    init->BaudRate = actual_baudrate; // remember actual baudrate for printing
-    if (20 * baudrate_diff > init->BaudRate) {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "set baudrate %d is not within 5%% of desired value", actual_baudrate));
-    }
-
-    return mp_const_none;
-}
-
-/// \classmethod \constructor(bus, ...)
-///
-/// Construct a UART object on the given bus.  `bus` can be 1-6, or 'XA', 'XB', 'YA', or 'YB'.
-/// With no additional parameters, the UART object is created but not
-/// initialised (it has the settings from the last initialisation of
-/// the bus, if any).  If extra arguments are given, the bus is initialised.
-/// See `init` for parameters of initialisation.
-///
-/// The physical pins of the UART busses are:
-///
-///   - `UART(4)` is on `XA`: `(TX, RX) = (X1, X2) = (PA0, PA1)`
-///   - `UART(1)` is on `XB`: `(TX, RX) = (X9, X10) = (PB6, PB7)`
-///   - `UART(6)` is on `YA`: `(TX, RX) = (Y1, Y2) = (PC6, PC7)`
-///   - `UART(3)` is on `YB`: `(TX, RX) = (Y9, Y10) = (PB10, PB11)`
-///   - `UART(2)` is on: `(TX, RX) = (X3, X4) = (PA2, PA3)`
-STATIC mp_obj_t pyb_uart_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
-    // check arguments
-    mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);
-
-    // work out port
-    int uart_id = 0;
-    if (MP_OBJ_IS_STR(args[0])) {
-        const char *port = mp_obj_str_get_str(args[0]);
-        if (0) {
-        #ifdef MICROPY_HW_UART1_NAME
-        } else if (strcmp(port, MICROPY_HW_UART1_NAME) == 0) {
-            uart_id = PYB_UART_1;
-        #endif
-        #ifdef MICROPY_HW_UART2_NAME
-        } else if (strcmp(port, MICROPY_HW_UART2_NAME) == 0) {
-            uart_id = PYB_UART_2;
-        #endif
-        #ifdef MICROPY_HW_UART3_NAME
-        } else if (strcmp(port, MICROPY_HW_UART3_NAME) == 0) {
-            uart_id = PYB_UART_3;
-        #endif
-        #ifdef MICROPY_HW_UART4_NAME
-        } else if (strcmp(port, MICROPY_HW_UART4_NAME) == 0) {
-            uart_id = PYB_UART_4;
-        #endif
-        #ifdef MICROPY_HW_UART5_NAME
-        } else if (strcmp(port, MICROPY_HW_UART5_NAME) == 0) {
-            uart_id = PYB_UART_5;
-        #endif
-        #ifdef MICROPY_HW_UART6_NAME
-        } else if (strcmp(port, MICROPY_HW_UART6_NAME) == 0) {
-            uart_id = PYB_UART_6;
-        #endif
-        #ifdef MICROPY_HW_UART7_NAME
-        } else if (strcmp(port, MICROPY_HW_UART7_NAME) == 0) {
-            uart_id = PYB_UART_7;
-        #endif
-        #ifdef MICROPY_HW_UART8_NAME
-        } else if (strcmp(port, MICROPY_HW_UART8_NAME) == 0) {
-            uart_id = PYB_UART_8;
-        #endif
-        } else {
-            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "UART(%s) doesn't exist", port));
-        }
-    } else {
-        uart_id = mp_obj_get_int(args[0]);
-        if (!uart_exists(uart_id)) {
-            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "UART(%d) doesn't exist", uart_id));
-        }
-    }
-
-    pyb_uart_obj_t *self;
-    if (MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1] == NULL) {
-        // create new UART object
-        self = m_new0(pyb_uart_obj_t, 1);
-        self->base.type = &pyb_uart_type;
-        self->uart_id = uart_id;
-        MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1] = self;
-    } else {
-        // reference existing UART object
-        self = MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1];
-    }
-
-    if (n_args > 1 || n_kw > 0) {
-        // start the peripheral
-        mp_map_t kw_args;
-        mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
-        pyb_uart_init_helper(self, n_args - 1, args + 1, &kw_args);
-    }
-
-    return MP_OBJ_FROM_PTR(self);
-}
-
-STATIC mp_obj_t pyb_uart_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
-    return pyb_uart_init_helper(MP_OBJ_TO_PTR(args[0]), n_args - 1, args + 1, kw_args);
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_uart_init_obj, 1, pyb_uart_init);
-
-/// \method deinit()
-/// Turn off the UART bus.
-STATIC mp_obj_t pyb_uart_deinit(mp_obj_t self_in) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    self->is_enabled = false;
-    UART_HandleTypeDef *uart = &self->uart;
-    HAL_UART_DeInit(uart);
-    if (uart->Instance == USART1) {
-        HAL_NVIC_DisableIRQ(USART1_IRQn);
-        __HAL_RCC_USART1_FORCE_RESET();
-        __HAL_RCC_USART1_RELEASE_RESET();
-        __HAL_RCC_USART1_CLK_DISABLE();
-    } else if (uart->Instance == USART2) {
-        HAL_NVIC_DisableIRQ(USART2_IRQn);
-        __HAL_RCC_USART2_FORCE_RESET();
-        __HAL_RCC_USART2_RELEASE_RESET();
-        __HAL_RCC_USART2_CLK_DISABLE();
-    #if defined(USART3)
-    } else if (uart->Instance == USART3) {
-        #if !defined(STM32F0)
-        HAL_NVIC_DisableIRQ(USART3_IRQn);
-        #endif
-        __HAL_RCC_USART3_FORCE_RESET();
-        __HAL_RCC_USART3_RELEASE_RESET();
-        __HAL_RCC_USART3_CLK_DISABLE();
-    #endif
-    #if defined(UART4)
-    } else if (uart->Instance == UART4) {
-        HAL_NVIC_DisableIRQ(UART4_IRQn);
-        __HAL_RCC_UART4_FORCE_RESET();
-        __HAL_RCC_UART4_RELEASE_RESET();
-        __HAL_RCC_UART4_CLK_DISABLE();
-    #endif
-    #if defined(USART4)
-    } else if (uart->Instance == USART4) {
-        __HAL_RCC_USART4_FORCE_RESET();
-        __HAL_RCC_USART4_RELEASE_RESET();
-        __HAL_RCC_USART4_CLK_DISABLE();
-    #endif
-    #if defined(UART5)
-    } else if (uart->Instance == UART5) {
-        HAL_NVIC_DisableIRQ(UART5_IRQn);
-        __HAL_RCC_UART5_FORCE_RESET();
-        __HAL_RCC_UART5_RELEASE_RESET();
-        __HAL_RCC_UART5_CLK_DISABLE();
-    #endif
-    #if defined(USART5)
-    } else if (uart->Instance == USART5) {
-        __HAL_RCC_USART5_FORCE_RESET();
-        __HAL_RCC_USART5_RELEASE_RESET();
-        __HAL_RCC_USART5_CLK_DISABLE();
-    #endif
-    #if defined(UART6)
-    } else if (uart->Instance == USART6) {
-        HAL_NVIC_DisableIRQ(USART6_IRQn);
-        __HAL_RCC_USART6_FORCE_RESET();
-        __HAL_RCC_USART6_RELEASE_RESET();
-        __HAL_RCC_USART6_CLK_DISABLE();
-    #endif
-    #if defined(UART7)
-    } else if (uart->Instance == UART7) {
-        HAL_NVIC_DisableIRQ(UART7_IRQn);
-        __HAL_RCC_UART7_FORCE_RESET();
-        __HAL_RCC_UART7_RELEASE_RESET();
-        __HAL_RCC_UART7_CLK_DISABLE();
-    #endif
-    #if defined(USART7)
-    } else if (uart->Instance == USART7) {
-        __HAL_RCC_USART7_FORCE_RESET();
-        __HAL_RCC_USART7_RELEASE_RESET();
-        __HAL_RCC_USART7_CLK_DISABLE();
-    #endif
-    #if defined(UART8)
-    } else if (uart->Instance == UART8) {
-        HAL_NVIC_DisableIRQ(UART8_IRQn);
-        __HAL_RCC_UART8_FORCE_RESET();
-        __HAL_RCC_UART8_RELEASE_RESET();
-        __HAL_RCC_UART8_CLK_DISABLE();
-    #endif
-    #if defined(USART8)
-    } else if (uart->Instance == USART8) {
-        __HAL_RCC_USART8_FORCE_RESET();
-        __HAL_RCC_USART8_RELEASE_RESET();
-        __HAL_RCC_USART8_CLK_DISABLE();
-    #endif
-    }
-    return mp_const_none;
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_deinit_obj, pyb_uart_deinit);
-
-/// \method any()
-/// Return `True` if any characters waiting, else `False`.
-STATIC mp_obj_t pyb_uart_any(mp_obj_t self_in) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    return MP_OBJ_NEW_SMALL_INT(uart_rx_any(self));
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_any_obj, pyb_uart_any);
-
-/// \method writechar(char)
-/// Write a single character on the bus.  `char` is an integer to write.
-/// Return value: `None`.
-STATIC mp_obj_t pyb_uart_writechar(mp_obj_t self_in, mp_obj_t char_in) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-
-    // get the character to write (might be 9 bits)
-    uint16_t data = mp_obj_get_int(char_in);
-
-    // write the character
-    int errcode;
-    if (uart_tx_wait(self, self->timeout)) {
-        uart_tx_data(self, &data, 1, &errcode);
-    } else {
-        errcode = MP_ETIMEDOUT;
-    }
-
-    if (errcode != 0) {
-        mp_raise_OSError(errcode);
-    }
-
-    return mp_const_none;
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_uart_writechar_obj, pyb_uart_writechar);
-
-/// \method readchar()
-/// Receive a single character on the bus.
-/// Return value: The character read, as an integer.  Returns -1 on timeout.
-STATIC mp_obj_t pyb_uart_readchar(mp_obj_t self_in) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    if (uart_rx_wait(self, self->timeout)) {
-        return MP_OBJ_NEW_SMALL_INT(uart_rx_char(self));
-    } else {
-        // return -1 on timeout
-        return MP_OBJ_NEW_SMALL_INT(-1);
-    }
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_readchar_obj, pyb_uart_readchar);
-
-// uart.sendbreak()
-STATIC mp_obj_t pyb_uart_sendbreak(mp_obj_t self_in) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    #if defined(STM32F0) || defined(STM32F7) || defined(STM32L4) || defined(STM32H7)
-    self->uart.Instance->RQR = USART_RQR_SBKRQ; // write-only register
-    #else
-    self->uart.Instance->CR1 |= USART_CR1_SBK;
-    #endif
-    return mp_const_none;
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_uart_sendbreak_obj, pyb_uart_sendbreak);
-
-STATIC const mp_rom_map_elem_t pyb_uart_locals_dict_table[] = {
-    // instance methods
-
-    { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&pyb_uart_init_obj) },
-    { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&pyb_uart_deinit_obj) },
-    { MP_ROM_QSTR(MP_QSTR_any), MP_ROM_PTR(&pyb_uart_any_obj) },
-
-    /// \method read([nbytes])
-    { MP_ROM_QSTR(MP_QSTR_read), MP_ROM_PTR(&mp_stream_read_obj) },
-    /// \method readline()
-    { MP_ROM_QSTR(MP_QSTR_readline), MP_ROM_PTR(&mp_stream_unbuffered_readline_obj)},
-    /// \method readinto(buf[, nbytes])
-    { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&mp_stream_readinto_obj) },
-    /// \method write(buf)
-    { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&mp_stream_write_obj) },
-
-    { MP_ROM_QSTR(MP_QSTR_writechar), MP_ROM_PTR(&pyb_uart_writechar_obj) },
-    { MP_ROM_QSTR(MP_QSTR_readchar), MP_ROM_PTR(&pyb_uart_readchar_obj) },
-    { MP_ROM_QSTR(MP_QSTR_sendbreak), MP_ROM_PTR(&pyb_uart_sendbreak_obj) },
-
-    // class constants
-    { MP_ROM_QSTR(MP_QSTR_RTS), MP_ROM_INT(UART_HWCONTROL_RTS) },
-    { MP_ROM_QSTR(MP_QSTR_CTS), MP_ROM_INT(UART_HWCONTROL_CTS) },
-};
-
-STATIC MP_DEFINE_CONST_DICT(pyb_uart_locals_dict, pyb_uart_locals_dict_table);
-
-STATIC mp_uint_t pyb_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, int *errcode) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    byte *buf = buf_in;
-
-    // check that size is a multiple of character width
-    if (size & self->char_width) {
-        *errcode = MP_EIO;
-        return MP_STREAM_ERROR;
-    }
-
-    // convert byte size to char size
-    size >>= self->char_width;
-
-    // make sure we want at least 1 char
-    if (size == 0) {
-        return 0;
-    }
-
-    // wait for first char to become available
-    if (!uart_rx_wait(self, self->timeout)) {
-        // return EAGAIN error to indicate non-blocking (then read() method returns None)
-        *errcode = MP_EAGAIN;
-        return MP_STREAM_ERROR;
-    }
-
-    // read the data
-    byte *orig_buf = buf;
-    for (;;) {
-        int data = uart_rx_char(self);
-        if (self->char_width == CHAR_WIDTH_9BIT) {
-            *(uint16_t*)buf = data;
-            buf += 2;
-        } else {
-            *buf++ = data;
-        }
-        if (--size == 0 || !uart_rx_wait(self, self->timeout_char)) {
-            // return number of bytes read
-            return buf - orig_buf;
-        }
-    }
-}
-
-STATIC mp_uint_t pyb_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t size, int *errcode) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    const byte *buf = buf_in;
-
-    // check that size is a multiple of character width
-    if (size & self->char_width) {
-        *errcode = MP_EIO;
-        return MP_STREAM_ERROR;
-    }
-
-    // wait to be able to write the first character. EAGAIN causes write to return None
-    if (!uart_tx_wait(self, self->timeout)) {
-        *errcode = MP_EAGAIN;
-        return MP_STREAM_ERROR;
-    }
-
-    // write the data
-    size_t num_tx = uart_tx_data(self, buf, size >> self->char_width, errcode);
-
-    if (*errcode == 0 || *errcode == MP_ETIMEDOUT) {
-        // return number of bytes written, even if there was a timeout
-        return num_tx << self->char_width;
-    } else {
-        return MP_STREAM_ERROR;
-    }
-}
-
-STATIC mp_uint_t pyb_uart_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr_t arg, int *errcode) {
-    pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    mp_uint_t ret;
-    if (request == MP_STREAM_POLL) {
-        uintptr_t flags = arg;
-        ret = 0;
-        if ((flags & MP_STREAM_POLL_RD) && uart_rx_any(self)) {
-            ret |= MP_STREAM_POLL_RD;
-        }
-        if ((flags & MP_STREAM_POLL_WR) && __HAL_UART_GET_FLAG(&self->uart, UART_FLAG_TXE)) {
-            ret |= MP_STREAM_POLL_WR;
-        }
-    } else {
-        *errcode = MP_EINVAL;
-        ret = MP_STREAM_ERROR;
-    }
-    return ret;
-}
-
-STATIC const mp_stream_p_t uart_stream_p = {
-    .read = pyb_uart_read,
-    .write = pyb_uart_write,
-    .ioctl = pyb_uart_ioctl,
-    .is_text = false,
-};
-
-const mp_obj_type_t pyb_uart_type = {
-    { &mp_type_type },
-    .name = MP_QSTR_UART,
-    .print = pyb_uart_print,
-    .make_new = pyb_uart_make_new,
-    .getiter = mp_identity_getiter,
-    .iternext = mp_stream_unbuffered_iter,
-    .protocol = &uart_stream_p,
-    .locals_dict = (mp_obj_dict_t*)&pyb_uart_locals_dict,
-};
diff --git a/ports/stm32/uart.h b/ports/stm32/uart.h
index 4ab18ff22..649cd7f9f 100644
--- a/ports/stm32/uart.h
+++ b/ports/stm32/uart.h
@@ -38,16 +38,41 @@ typedef enum {
     PYB_UART_8 = 8,
 } pyb_uart_t;
 
-typedef struct _pyb_uart_obj_t pyb_uart_obj_t;
+#define CHAR_WIDTH_8BIT (0)
+#define CHAR_WIDTH_9BIT (1)
+
+typedef struct _pyb_uart_obj_t {
+    mp_obj_base_t base;
+    UART_HandleTypeDef uart;            // this is 17 words big
+    IRQn_Type irqn;
+    pyb_uart_t uart_id : 8;
+    bool is_enabled : 1;
+    bool attached_to_repl;              // whether the UART is attached to REPL
+    byte char_width;                    // 0 for 7,8 bit chars, 1 for 9 bit chars
+    uint16_t char_mask;                 // 0x7f for 7 bit, 0xff for 8 bit, 0x1ff for 9 bit
+    uint16_t timeout;                   // timeout waiting for first char
+    uint16_t timeout_char;              // timeout waiting between chars
+    uint16_t read_buf_len;              // len in chars; buf can hold len-1 chars
+    volatile uint16_t read_buf_head;    // indexes first empty slot
+    uint16_t read_buf_tail;             // indexes first full slot (not full if equals head)
+    byte *read_buf;                     // byte or uint16_t, depending on char size
+} pyb_uart_obj_t;
+
 extern const mp_obj_type_t pyb_uart_type;
 
 void uart_init0(void);
-void uart_deinit(void);
+void uart_deinit_all(void);
+bool uart_exists(int uart_id);
+bool uart_init2(pyb_uart_obj_t *uart_obj);
+void uart_deinit(pyb_uart_obj_t *uart_obj);
 void uart_irq_handler(mp_uint_t uart_id);
 
 void uart_attach_to_repl(pyb_uart_obj_t *self, bool attached);
 mp_uint_t uart_rx_any(pyb_uart_obj_t *uart_obj);
+bool uart_rx_wait(pyb_uart_obj_t *self, uint32_t timeout);
 int uart_rx_char(pyb_uart_obj_t *uart_obj);
+bool uart_tx_wait(pyb_uart_obj_t *self, uint32_t timeout);
+size_t uart_tx_data(pyb_uart_obj_t *self, const void *src_in, size_t num_chars, int *errcode);
 void uart_tx_strn(pyb_uart_obj_t *uart_obj, const char *str, uint len);
 
 #endif // MICROPY_INCLUDED_STM32_UART_H