alif/machine_uart: Add machine.UART peripheral support.

Signed-off-by: Damien George <damien@micropython.org>

2 files changed, 563 insertions, 0 deletions

diff --git a/ports/alif/machine_uart.c b/ports/alif/machine_uart.c
new file mode 100644
index 000000000..746c86677
--- /dev/null
+++ b/ports/alif/machine_uart.c
@@ -0,0 +1,560 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2025 OpenMV LLC.
+ *
+ * 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.
+ */
+
+// This file is never compiled standalone, it's included directly from
+// extmod/machine_uart.c via MICROPY_PY_MACHINE_UART_INCLUDEFILE.
+
+#include "py/mphal.h"
+#include "py/mperrno.h"
+#include "mpuart.h"
+
+#define DEFAULT_UART_BAUDRATE (115200)
+#define DEFAULT_UART_BITS (8)
+#define DEFAULT_UART_PARITY (MP_ROM_NONE)
+#define DEFAULT_UART_STOP (1)
+#define DEFAULT_UART_RX_BUFFER_SIZE (256)
+
+typedef struct _machine_uart_obj_t {
+    mp_obj_base_t base;
+    unsigned int uart_id;
+    uint32_t baudrate;
+    UART_DATA_BITS bits;
+    UART_PARITY parity;
+    UART_STOP_BITS stop;
+    mp_hal_pin_obj_t tx;
+    mp_hal_pin_obj_t rx;
+    mp_hal_pin_obj_t rts;
+    mp_hal_pin_obj_t cts;
+    uint32_t flow;
+    uint16_t timeout;       // timeout waiting for first char (in ms)
+    uint16_t timeout_char;  // timeout waiting between chars (in ms)
+    uint8_t *rx_ringbuf_array;
+    ringbuf_t rx_ringbuf;
+    uint32_t irq_flags;
+    uint32_t irq_trigger;
+    mp_irq_obj_t irq_obj;
+} machine_uart_obj_t;
+
+typedef struct _machine_uart_default_pins_t {
+    mp_hal_pin_obj_t tx;
+    mp_hal_pin_obj_t rx;
+    mp_hal_pin_obj_t rts;
+    mp_hal_pin_obj_t cts;
+} machine_uart_default_pins_t;
+
+static const machine_uart_default_pins_t machine_uart_default_pins[UART_MAX] = {
+    [0] = {
+        #if defined(MICROPY_HW_UART0_TX) && defined(MICROPY_HW_UART0_RX)
+        MICROPY_HW_UART0_TX, MICROPY_HW_UART0_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART0_RTS) && defined(MICROPY_HW_UART0_CTS)
+        MICROPY_HW_UART0_RTS, MICROPY_HW_UART0_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [1] = {
+        #if defined(MICROPY_HW_UART1_TX) && defined(MICROPY_HW_UART1_RX)
+        MICROPY_HW_UART1_TX, MICROPY_HW_UART1_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART1_RTS) && defined(MICROPY_HW_UART1_CTS)
+        MICROPY_HW_UART1_RTS, MICROPY_HW_UART1_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [2] = {
+        #if defined(MICROPY_HW_UART2_TX) && defined(MICROPY_HW_UART2_RX)
+        MICROPY_HW_UART2_TX, MICROPY_HW_UART2_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART2_RTS) && defined(MICROPY_HW_UART2_CTS)
+        MICROPY_HW_UART2_RTS, MICROPY_HW_UART2_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [3] = {
+        #if defined(MICROPY_HW_UART3_TX) && defined(MICROPY_HW_UART3_RX)
+        MICROPY_HW_UART3_TX, MICROPY_HW_UART3_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART3_RTS) && defined(MICROPY_HW_UART3_CTS)
+        MICROPY_HW_UART3_RTS, MICROPY_HW_UART3_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [4] = {
+        #if defined(MICROPY_HW_UART4_TX) && defined(MICROPY_HW_UART4_RX)
+        MICROPY_HW_UART4_TX, MICROPY_HW_UART4_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART4_RTS) && defined(MICROPY_HW_UART4_CTS)
+        MICROPY_HW_UART4_RTS, MICROPY_HW_UART4_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [5] = {
+        #if defined(MICROPY_HW_UART5_TX) && defined(MICROPY_HW_UART5_RX)
+        MICROPY_HW_UART5_TX, MICROPY_HW_UART5_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART5_RTS) && defined(MICROPY_HW_UART5_CTS)
+        MICROPY_HW_UART5_RTS, MICROPY_HW_UART5_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [6] = {
+        #if defined(MICROPY_HW_UART6_TX) && defined(MICROPY_HW_UART6_RX)
+        MICROPY_HW_UART6_TX, MICROPY_HW_UART6_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART6_RTS) && defined(MICROPY_HW_UART6_CTS)
+        MICROPY_HW_UART6_RTS, MICROPY_HW_UART6_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+    [7] = {
+        #if defined(MICROPY_HW_UART7_TX) && defined(MICROPY_HW_UART7_RX)
+        MICROPY_HW_UART7_TX, MICROPY_HW_UART7_RX,
+        #else
+        NULL, NULL,
+        #endif
+        #if defined(MICROPY_HW_UART7_RTS) && defined(MICROPY_HW_UART7_CTS)
+        MICROPY_HW_UART7_RTS, MICROPY_HW_UART7_CTS,
+        #else
+        NULL, NULL,
+        #endif
+    },
+};
+
+static void machine_uart_irq_callback(unsigned int uart_id, unsigned int trigger);
+
+MP_REGISTER_ROOT_POINTER(struct _machine_uart_obj_t *machine_uart_obj_all[UART_MAX]);
+
+/******************************************************************************/
+// MicroPython bindings for UART
+
+#define MICROPY_PY_MACHINE_UART_CLASS_CONSTANTS \
+    { MP_ROM_QSTR(MP_QSTR___del__), MP_ROM_PTR(&machine_uart___del___obj) }, \
+    { MP_ROM_QSTR(MP_QSTR_RTS), MP_ROM_INT(UART_FLOW_CONTROL_RTS) }, \
+    { MP_ROM_QSTR(MP_QSTR_CTS), MP_ROM_INT(UART_FLOW_CONTROL_CTS) }, \
+    { MP_ROM_QSTR(MP_QSTR_IRQ_RX), MP_ROM_INT(MP_UART_IRQ_RX) }, \
+    { MP_ROM_QSTR(MP_QSTR_IRQ_RXIDLE), MP_ROM_INT(MP_UART_IRQ_RXIDLE) }, \
+    { MP_ROM_QSTR(MP_QSTR_IRQ_TXIDLE), MP_ROM_INT(MP_UART_IRQ_TXIDLE) }, \
+
+#define GET_PIN_WITH_DEFAULT(uart_id_, pin_name, pin_selection) \
+    (pin_selection == mp_const_none ? machine_uart_default_pins[uart_id_].pin_name : mp_hal_get_pin_obj(pin_selection))
+
+static void machine_uart_set_bits(machine_uart_obj_t *self, mp_int_t bits) {
+    if (!(5 <= bits && bits <= 8)) {
+        mp_raise_ValueError(MP_ERROR_TEXT("invalid bits"));
+    }
+    self->bits = UART_DATA_BITS_5 + (bits - 5);
+}
+
+static void machine_uart_set_parity(machine_uart_obj_t *self, mp_obj_t parity) {
+    if (parity == mp_const_none) {
+        self->parity = UART_PARITY_NONE;
+    } else if (mp_obj_get_int(parity) & 1) {
+        self->parity = UART_PARITY_ODD;
+    } else {
+        self->parity = UART_PARITY_EVEN;
+    }
+}
+
+static void machine_uart_set_stop(machine_uart_obj_t *self, mp_int_t stop) {
+    if (!(1 <= stop && stop <= 2)) {
+        mp_raise_ValueError(MP_ERROR_TEXT("invalid stop"));
+    }
+    self->stop = UART_STOP_BITS_1 + (stop - 1);
+}
+
+static void machine_uart_set_timeout_char(machine_uart_obj_t *self, mp_int_t timeout_char) {
+    // Make sure timeout_char is at least as long as a whole character (13 bits to be safe).
+    uint32_t min_timeout_char = 13000 / self->baudrate + 1;
+    self->timeout_char = MAX(min_timeout_char, timeout_char);
+}
+
+static void mp_machine_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    static const char *parity_name[] = {[UART_PARITY_NONE] = "None", [UART_PARITY_EVEN] = "0", [UART_PARITY_ODD] = "1"};
+
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    unsigned int bits = 5 + (self->bits - UART_DATA_BITS_5);
+    const char *parity = parity_name[self->parity];
+    unsigned int stop = 1 + (self->stop - UART_STOP_BITS_1);
+
+    mp_printf(print, "UART(%u, baudrate=%u, bits=%u, parity=%s, stop=%u, "
+        "tx=%q, rx=%q, ",
+        self->uart_id, self->baudrate, bits, parity, stop,
+        mp_hal_pin_name(self->tx), mp_hal_pin_name(self->rx));
+    if (self->rts != NULL) {
+        mp_printf(print, "rts=%q, ", mp_hal_pin_name(self->rts));
+    }
+    if (self->cts != NULL) {
+        mp_printf(print, "cts=%q, ", mp_hal_pin_name(self->cts));
+    }
+    mp_printf(print, "flow=", self->rts);
+    if (self->flow == 0) {
+        mp_printf(print, "0");
+    } else {
+        if (self->flow & UART_FLOW_CONTROL_RTS) {
+            mp_printf(print, "RTS");
+            if (self->flow & UART_FLOW_CONTROL_CTS) {
+                mp_printf(print, "|");
+            }
+        }
+        if (self->flow & UART_FLOW_CONTROL_CTS) {
+            mp_printf(print, "CTS");
+        }
+    }
+    mp_printf(print, ", timeout=%u, timeout_char=%u, rxbuf=%u)",
+        self->timeout, self->timeout_char, self->rx_ringbuf.size - 1);
+}
+
+static mp_obj_t mp_machine_uart_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    enum {
+        ARG_id,
+        ARG_baudrate, ARG_bits, ARG_parity, ARG_stop,
+        ARG_tx, ARG_rx, ARG_rts, ARG_cts,
+        ARG_flow, ARG_timeout, ARG_timeout_char, ARG_rxbuf,
+    };
+    static const mp_arg_t allowed_args[] = {
+        #if !defined(MICROPY_HW_DEFAULT_UART_ID)
+        { MP_QSTR_id, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = -1} },
+        #else
+        { MP_QSTR_id, MP_ARG_INT, {.u_int = MICROPY_HW_DEFAULT_UART_ID} },
+        #endif
+        { MP_QSTR_baudrate, MP_ARG_INT, {.u_int = DEFAULT_UART_BAUDRATE} },
+        { MP_QSTR_bits, MP_ARG_INT, {.u_int = DEFAULT_UART_BITS} },
+        { MP_QSTR_parity, MP_ARG_OBJ, {.u_rom_obj = DEFAULT_UART_PARITY} },
+        { MP_QSTR_stop, MP_ARG_INT, {.u_int = DEFAULT_UART_STOP} },
+        { MP_QSTR_tx, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_rx, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_rts, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_cts, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_flow, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+        { 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 = DEFAULT_UART_RX_BUFFER_SIZE} },
+    };
+
+    // Parse args.
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    // Get UART bus.
+    int uart_id = args[ARG_id].u_int;
+    if (uart_id < 0 || uart_id >= UART_MAX) {
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("UART(%d) doesn't exist"), uart_id);
+    }
+
+    machine_uart_obj_t *self;
+    bool need_init;
+    if (MP_STATE_PORT(machine_uart_obj_all)[uart_id] == NULL) {
+        // Create new UART object.
+        self = mp_obj_malloc_with_finaliser(machine_uart_obj_t, &machine_uart_type);
+        self->uart_id = uart_id;
+        need_init = true;
+    } else {
+        // Reference existing UART object.
+        self = MP_STATE_PORT(machine_uart_obj_all)[uart_id];
+        need_init = n_args > 1 || n_kw > 0;
+    }
+
+    if (need_init) {
+        // Set the UART parameters.
+        self->baudrate = args[ARG_baudrate].u_int;
+        machine_uart_set_bits(self, args[ARG_bits].u_int);
+        machine_uart_set_parity(self, args[ARG_parity].u_obj);
+        machine_uart_set_stop(self, args[ARG_stop].u_int);
+        self->tx = GET_PIN_WITH_DEFAULT(self->uart_id, tx, args[ARG_tx].u_obj);
+        self->rx = GET_PIN_WITH_DEFAULT(self->uart_id, rx, args[ARG_rx].u_obj);
+        self->rts = GET_PIN_WITH_DEFAULT(self->uart_id, rts, args[ARG_rts].u_obj);
+        self->cts = GET_PIN_WITH_DEFAULT(self->uart_id, cts, args[ARG_cts].u_obj);
+        self->flow = args[ARG_flow].u_int;
+        self->timeout = args[ARG_timeout].u_int;
+        uint32_t min_timeout_char = 13000 / self->baudrate + 1; // 13 bits to be safe
+        self->timeout = MAX(min_timeout_char, args[ARG_timeout_char].u_int);
+
+        // Check TX/RX pins are given.
+        if (self->tx == NULL) {
+            mp_raise_ValueError(MP_ERROR_TEXT("tx not given"));
+        }
+        if (self->rx == NULL) {
+            mp_raise_ValueError(MP_ERROR_TEXT("rx not given"));
+        }
+
+        // Configure flow control.
+        mp_hal_pin_obj_t rts = NULL;
+        mp_hal_pin_obj_t cts = NULL;
+        if (self->flow & UART_FLOW_CONTROL_RTS) {
+            if (self->rts == NULL) {
+                mp_raise_ValueError(MP_ERROR_TEXT("rts not given"));
+            }
+            rts = self->rts;
+        }
+        if (self->flow & UART_FLOW_CONTROL_CTS) {
+            if (self->cts == NULL) {
+                mp_raise_ValueError(MP_ERROR_TEXT("cts not given"));
+            }
+            cts = self->cts;
+        }
+
+        // Allocate the RX buffer.
+        size_t rxbuf_len = args[ARG_rxbuf].u_int;
+        self->rx_ringbuf_array = m_new(uint8_t, rxbuf_len + 1);
+        self->rx_ringbuf.buf = self->rx_ringbuf_array;
+        self->rx_ringbuf.size = rxbuf_len + 1;
+        self->rx_ringbuf.iput = 0;
+        self->rx_ringbuf.iget = 0;
+
+        // Reset the IRQ state
+        self->irq_flags = 0;
+        self->irq_trigger = 0;
+        self->irq_obj.base.type = NULL;
+
+        // Initialize the UART hardware.
+        mp_uart_init(self->uart_id, self->baudrate, self->bits, self->parity, self->stop, self->tx, self->rx, &self->rx_ringbuf);
+
+        mp_uart_set_flow(self->uart_id, rts, cts);
+    }
+
+    MP_STATE_PORT(machine_uart_obj_all)[uart_id] = self;
+
+    return MP_OBJ_FROM_PTR(self);
+}
+
+static void mp_machine_uart_init_helper(machine_uart_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum {
+        ARG_baudrate, ARG_bits, ARG_parity, ARG_stop,
+        ARG_timeout, ARG_timeout_char,
+    };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_baudrate, MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_bits, MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_parity, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_INT(-1)} },
+        { MP_QSTR_stop, MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_timeout_char, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
+    };
+
+    // Parse args.
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    bool change_baudrate = false;
+    bool change_bits_parity_stop = false;
+
+    // Change baudrate if requested.
+    if (args[ARG_baudrate].u_int > 0) {
+        self->baudrate = args[ARG_baudrate].u_int;
+        change_baudrate = true;
+    }
+
+    // Change data bits if requested.
+    if (args[ARG_bits].u_int > 0) {
+        machine_uart_set_bits(self, args[ARG_bits].u_int);
+        change_bits_parity_stop = true;
+    }
+
+    // Change parity if requested.
+    if (args[ARG_parity].u_obj != MP_OBJ_NEW_SMALL_INT(-1)) {
+        machine_uart_set_parity(self, args[ARG_parity].u_obj);
+        change_bits_parity_stop = true;
+    }
+
+    // Change stop bits if requested.
+    if (args[ARG_stop].u_int > 0) {
+        machine_uart_set_stop(self, args[ARG_stop].u_int);
+        change_bits_parity_stop = true;
+    }
+
+    // Change timeout if requested.
+    if (args[ARG_timeout].u_int >= 0) {
+        self->timeout = args[ARG_timeout].u_int;
+    }
+
+    // Change timeout_char if requested.
+    if (args[ARG_timeout_char].u_int >= 0) {
+        machine_uart_set_timeout_char(self, args[ARG_timeout_char].u_int);
+    }
+
+    // Reconfigure the hardware parameters that have changed.
+    if (change_baudrate) {
+        mp_uart_set_baudrate(self->uart_id, self->baudrate);
+    }
+    if (change_bits_parity_stop) {
+        mp_uart_set_bits_parity_stop(self->uart_id, self->bits, self->parity, self->stop);
+    }
+}
+
+static mp_obj_t machine_uart___del__(mp_obj_t self_in) {
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_uart_deinit(self->uart_id);
+    MP_STATE_PORT(machine_uart_obj_all)[self->uart_id] = NULL;
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(machine_uart___del___obj, machine_uart___del__);
+
+// Turn off the UART bus.
+static void mp_machine_uart_deinit(machine_uart_obj_t *self) {
+    mp_uart_deinit(self->uart_id);
+}
+
+// Return number of characters waiting.
+static mp_int_t mp_machine_uart_any(machine_uart_obj_t *self) {
+    return mp_uart_rx_any(self->uart_id);
+}
+
+// Since uart.write() waits up to the last byte, uart.txdone() always returns True.
+static bool mp_machine_uart_txdone(machine_uart_obj_t *self) {
+    return !!mp_uart_tx_any(self->uart_id);
+}
+
+// Change the trigger for the UART IRQ.
+static mp_uint_t machine_uart_irq_trigger(mp_obj_t self_in, mp_uint_t new_trigger) {
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    self->irq_trigger = new_trigger;
+    mp_uart_set_irq_callback(self->uart_id, self->irq_trigger, machine_uart_irq_callback);
+    return 0;
+}
+
+// Get UART IRQ state.
+static mp_uint_t machine_uart_irq_info(mp_obj_t self_in, mp_uint_t info_type) {
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    if (info_type == MP_IRQ_INFO_FLAGS) {
+        return self->irq_flags;
+    } else if (info_type == MP_IRQ_INFO_TRIGGERS) {
+        return self->irq_trigger;
+    }
+    return 0;
+}
+
+static const mp_irq_methods_t machine_uart_irq_methods = {
+    .trigger = machine_uart_irq_trigger,
+    .info = machine_uart_irq_info,
+};
+
+// Retrieve and configure the UART IRQ object.
+static mp_irq_obj_t *mp_machine_uart_irq(machine_uart_obj_t *self, bool any_args, mp_arg_val_t *args) {
+    if (self->irq_obj.base.type == NULL) {
+        mp_irq_init(&self->irq_obj, &machine_uart_irq_methods, MP_OBJ_FROM_PTR(self));
+    }
+
+    if (any_args) {
+        self->irq_obj.handler = args[MP_IRQ_ARG_INIT_handler].u_obj;
+        self->irq_obj.ishard = args[MP_IRQ_ARG_INIT_hard].u_bool;
+        machine_uart_irq_trigger(MP_OBJ_FROM_PTR(self), args[MP_IRQ_ARG_INIT_trigger].u_int);
+    }
+
+    return &self->irq_obj;
+}
+
+static mp_uint_t mp_machine_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, int *errcode) {
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_uint_t start = mp_hal_ticks_ms();
+    mp_uint_t timeout = self->timeout;
+    uint8_t *dest = buf_in;
+
+    for (size_t i = 0; i < size; i++) {
+        // Wait for the first/next character
+        while (!mp_uart_rx_any(self->uart_id)) {
+            mp_uint_t elapsed = mp_hal_ticks_ms() - start;
+            if (elapsed > timeout) {  // timed out
+                if (i <= 0) {
+                    *errcode = MP_EAGAIN;
+                    return MP_STREAM_ERROR;
+                } else {
+                    return i;
+                }
+            }
+            mp_event_handle_nowait();
+        }
+        *dest++ = mp_uart_rx_char(self->uart_id);
+        start = mp_hal_ticks_ms(); // Inter-character timeout
+        timeout = self->timeout_char;
+    }
+    return size;
+}
+
+static mp_uint_t mp_machine_uart_write(mp_obj_t self_in, const void *buf_in, mp_uint_t size, int *errcode) {
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_uart_tx_data(self->uart_id, buf_in, size);
+    return size;
+}
+
+static mp_uint_t mp_machine_uart_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr_t arg, int *errcode) {
+    machine_uart_obj_t *self = self_in;
+    mp_uint_t ret;
+    if (request == MP_STREAM_POLL) {
+        uintptr_t flags = arg;
+        ret = 0;
+        if ((flags & MP_STREAM_POLL_RD) && mp_uart_rx_any(self->uart_id)) {
+            ret |= MP_STREAM_POLL_RD;
+        }
+        if ((flags & MP_STREAM_POLL_WR)) {
+            ret |= MP_STREAM_POLL_WR;
+        }
+    } else if (request == MP_STREAM_FLUSH) {
+        uint32_t t0 = mp_hal_ticks_ms();
+        const uint32_t timeout_ms = 100 + 10 * mp_uart_tx_any(self->uart_id);
+        while (mp_uart_tx_any(self->uart_id)) {
+            if (mp_hal_ticks_ms() - t0 > timeout_ms) {
+                *errcode = MP_ETIMEDOUT;
+                ret = MP_STREAM_ERROR;
+            }
+            mp_event_handle_nowait();
+        }
+        return 0;
+    } else {
+        *errcode = MP_EINVAL;
+        ret = MP_STREAM_ERROR;
+    }
+    return ret;
+}
+
+static void machine_uart_irq_callback(unsigned int uart_id, unsigned int trigger) {
+    machine_uart_obj_t *self = MP_STATE_PORT(machine_uart_obj_all)[uart_id];
+    self->irq_flags = trigger;
+    if (self->irq_obj.base.type != NULL && (self->irq_flags & self->irq_trigger)) {
+        mp_irq_handler(&self->irq_obj);
+    }
+}
diff --git a/ports/alif/mpconfigport.h b/ports/alif/mpconfigport.h
index 73abb8924..6c9e6af63 100644
--- a/ports/alif/mpconfigport.h
+++ b/ports/alif/mpconfigport.h
@@ -136,6 +136,9 @@
 #define MICROPY_PY_MACHINE_SPI                  (1)
 #define MICROPY_PY_MACHINE_SOFTSPI              (1)
 #define MICROPY_PY_MACHINE_TIMER                (1)
+#define MICROPY_PY_MACHINE_UART                 (1)
+#define MICROPY_PY_MACHINE_UART_INCLUDEFILE     "ports/alif/machine_uart.c"
+#define MICROPY_PY_MACHINE_UART_IRQ             (1)
 #define MICROPY_PY_NETWORK                      (CORE_M55_HP)
 #ifndef MICROPY_PY_NETWORK_HOSTNAME_DEFAULT
 #define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT     "mpy-alif"