Diff: targets/TARGET_NORDIC/TARGET_NRF5/serial_api.c

Revision:

149:156823d33999

Child:

150:02e0a0aed4ec

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NORDIC/TARGET_NRF5/serial_api.c	Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,638 @@
+/* 
+ * Copyright (c) 2013 Nordic Semiconductor ASA
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   1. Redistributions of source code must retain the above copyright notice, this list 
+ *      of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form, except as embedded into a Nordic Semiconductor ASA 
+ *      integrated circuit in a product or a software update for such product, must reproduce 
+ *      the above copyright notice, this list of conditions and the following disclaimer in 
+ *      the documentation and/or other materials provided with the distribution.
+ *
+ *   3. Neither the name of Nordic Semiconductor ASA nor the names of its contributors may be 
+ *      used to endorse or promote products derived from this software without specific prior 
+ *      written permission.
+ *
+ *   4. This software, with or without modification, must only be used with a 
+ *      Nordic Semiconductor ASA integrated circuit.
+ *
+ *   5. Any software provided in binary or object form under this license must not be reverse 
+ *      engineered, decompiled, modified and/or disassembled. 
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * 
+ */
+
+#include "serial_api.h"
+
+#if DEVICE_SERIAL
+
+#include <string.h>
+#include "mbed_assert.h"
+#include "mbed_error.h"
+#include "nrf_uart.h"
+#include "nrf_drv_common.h"
+#include "nrf_drv_config.h"
+#include "app_util_platform.h"
+#include "nrf_gpio.h"
+
+#define UART_INSTANCE_COUNT 1
+#define UART_INSTANCE       NRF_UART0
+#define UART_IRQn           UART0_IRQn
+#define UART_IRQ_HANDLER    UART0_IRQHandler
+#define UART_INSTANCE_ID    0
+#define UART_CB uart_cb[UART_INSTANCE_ID]
+
+#define UART_DEFAULT_BAUDRATE   UART0_CONFIG_BAUDRATE
+#define UART_DEFAULT_PARITY     UART0_CONFIG_PARITY
+
+// expected the macro from mbed configuration system
+#ifndef MBED_CONF_NORDIC_UART_HWFC
+    #define MBED_CONF_NORDIC_UART_HWFC 1
+    #warning None of UART flow control configuration (expected macro MBED_CONF_NORDIC_UART_HWFC). The RTSCTS flow control is used by default .
+#endif
+
+#if MBED_CONF_NORDIC_UART_HWFC == 1
+    #define UART_DEFAULT_HWFC       UART0_CONFIG_HWFC
+#else
+    #define UART_DEFAULT_HWFC  NRF_UART_HWFC_DISABLED
+#endif
+
+#define UART_DEFAULT_CTS        UART0_CONFIG_PSEL_CTS
+#define UART_DEFAULT_RTS        UART0_CONFIG_PSEL_RTS
+
+// Required by "retarget.cpp".
+int stdio_uart_inited = 0;
+serial_t stdio_uart;
+
+typedef struct {
+    bool                initialized;
+    uint32_t            irq_context;
+    uart_irq_handler    irq_handler;
+
+    uint32_t            pselrxd;
+    uint32_t            pseltxd;
+    uint32_t            pselcts;
+    uint32_t            pselrts;
+    nrf_uart_hwfc_t     hwfc;
+    nrf_uart_parity_t   parity;
+    nrf_uart_baudrate_t baudrate;
+
+#if DEVICE_SERIAL_ASYNCH
+    bool volatile       rx_active;
+    uint8_t            *rx_buffer;
+    size_t              rx_length;
+    size_t              rx_pos;
+    void              (*rx_asynch_handler)();
+    uint8_t             char_match;
+
+    bool volatile       tx_active;
+    const uint8_t      *tx_buffer;
+    size_t              tx_length;
+    size_t              tx_pos;
+    void              (*tx_asynch_handler)();
+
+    uint32_t            events_wanted;
+    uint32_t            events_occured;
+
+    #define UART_IRQ_TX 1
+    #define UART_IRQ_RX 2
+    uint8_t             irq_enabled;
+#endif // DEVICE_SERIAL_ASYNCH
+} uart_ctlblock_t;
+
+static uart_ctlblock_t uart_cb[UART_INSTANCE_COUNT];
+
+
+#if DEVICE_SERIAL_ASYNCH
+static void end_asynch_rx(void)
+{
+    // If RX interrupt is activated for synchronous operations,
+    // don't disable it, just stop handling it here.
+    if (!(UART_CB.irq_enabled & UART_IRQ_RX)) {
+        nrf_uart_int_disable(UART_INSTANCE, NRF_UART_INT_MASK_RXDRDY);
+    }
+    UART_CB.rx_active = false;
+}
+static void end_asynch_tx(void)
+{
+    // If TX interrupt is activated for synchronous operations,
+    // don't disable it, just stop handling it here.
+    if (!(UART_CB.irq_enabled & UART_IRQ_TX)) {
+        nrf_uart_int_disable(UART_INSTANCE, NRF_UART_INT_MASK_TXDRDY);
+    }
+    UART_CB.tx_active = false;
+}
+#endif // DEVICE_SERIAL_ASYNCH
+
+void UART_IRQ_HANDLER(void)
+{
+    if (nrf_uart_int_enable_check(UART_INSTANCE, NRF_UART_INT_MASK_RXDRDY) &&
+        nrf_uart_event_check(UART_INSTANCE, NRF_UART_EVENT_RXDRDY)) {
+
+    #if DEVICE_SERIAL_ASYNCH
+        if (UART_CB.rx_active) {
+            nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_RXDRDY);
+
+            uint8_t rx_data = nrf_uart_rxd_get(UART_INSTANCE);
+            UART_CB.rx_buffer[UART_CB.rx_pos] = rx_data;
+
+            bool end_rx = false;
+            // If character matching should be performed, check if the current
+            // data matches the given one.
+            if (UART_CB.char_match != SERIAL_RESERVED_CHAR_MATCH &&
+                rx_data == UART_CB.char_match) {
+                // If it does, report the match and abort further receiving.
+                UART_CB.events_occured |= SERIAL_EVENT_RX_CHARACTER_MATCH;
+                if (UART_CB.events_wanted & SERIAL_EVENT_RX_CHARACTER_MATCH) {
+                    end_rx = true;
+                }
+            }
+            if (++UART_CB.rx_pos >= UART_CB.rx_length) {
+                UART_CB.events_occured |= SERIAL_EVENT_RX_COMPLETE;
+                end_rx = true;
+            }
+            if (end_rx) {
+                end_asynch_rx();
+
+                if (UART_CB.rx_asynch_handler) {
+                    // Use local variable to make it possible to start a next
+                    // transfer from callback routine.
+                    void (*handler)() = UART_CB.rx_asynch_handler;
+                    UART_CB.rx_asynch_handler = NULL;
+                    handler();
+                }
+            }
+        }
+        else
+    #endif
+
+        if (UART_CB.irq_handler) {
+            UART_CB.irq_handler(UART_CB.irq_context, RxIrq);
+        }
+    }
+
+    if (nrf_uart_int_enable_check(UART_INSTANCE, NRF_UART_INT_MASK_TXDRDY) &&
+        nrf_uart_event_check(UART_INSTANCE, NRF_UART_EVENT_TXDRDY)) {
+
+    #if DEVICE_SERIAL_ASYNCH
+        if (UART_CB.tx_active) {
+            if (++UART_CB.tx_pos <= UART_CB.tx_length) {
+                // When there is still something to send, clear the TXDRDY event
+                // and put next byte to transmitter.
+                nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_TXDRDY);
+                nrf_uart_txd_set(UART_INSTANCE,
+                    UART_CB.tx_buffer[UART_CB.tx_pos]);
+            }
+            else {
+                // When the TXDRDY event is set after the last byte to be sent
+                // has been passed to the transmitter, the job is done and TX
+                // complete can be indicated.
+                // Don't clear the TXDRDY event, it needs to remain set for the
+                // 'serial_writable' function to work properly.
+                end_asynch_tx();
+
+                UART_CB.events_occured |= SERIAL_EVENT_TX_COMPLETE;
+                if (UART_CB.tx_asynch_handler) {
+                    // Use local variable to make it possible to start a next
+                    // transfer from callback routine.
+                    void (*handler)() = UART_CB.tx_asynch_handler;
+                    UART_CB.tx_asynch_handler = NULL;
+                    handler();
+                }
+            }
+        }
+        else
+    #endif
+
+        if (UART_CB.irq_handler) {
+            UART_CB.irq_handler(UART_CB.irq_context, TxIrq);
+        }
+    }
+
+#if DEVICE_SERIAL_ASYNCH
+    if (nrf_uart_event_check(UART_INSTANCE, NRF_UART_EVENT_ERROR)) {
+        nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_ERROR);
+
+        uint8_t errorsrc = nrf_uart_errorsrc_get_and_clear(UART_INSTANCE);
+        if (UART_CB.rx_asynch_handler) {
+            UART_CB.events_occured |= SERIAL_EVENT_ERROR;
+            if (errorsrc & NRF_UART_ERROR_PARITY_MASK) {
+                UART_CB.events_occured |= SERIAL_EVENT_RX_PARITY_ERROR;
+            }
+            if (errorsrc & NRF_UART_ERROR_FRAMING_MASK) {
+                UART_CB.events_occured |= SERIAL_EVENT_RX_FRAMING_ERROR;
+            }
+            if (errorsrc & NRF_UART_ERROR_OVERRUN_MASK) {
+                UART_CB.events_occured |= SERIAL_EVENT_RX_OVERRUN_ERROR;
+            }
+            UART_CB.rx_asynch_handler();
+        }
+    }
+#endif // DEVICE_SERIAL_ASYNCH
+}
+
+void serial_init(serial_t *obj, PinName tx, PinName rx) {
+    UART_CB.pseltxd =
+        (tx == NC) ? NRF_UART_PSEL_DISCONNECTED : (uint32_t)tx;
+    UART_CB.pselrxd =
+        (rx == NC) ? NRF_UART_PSEL_DISCONNECTED : (uint32_t)rx;
+    if (UART_CB.pseltxd != NRF_UART_PSEL_DISCONNECTED) {
+        nrf_gpio_pin_set(UART_CB.pseltxd);
+        nrf_gpio_cfg_output(UART_CB.pseltxd);
+    }
+    if (UART_CB.pselrxd != NRF_UART_PSEL_DISCONNECTED) {
+        nrf_gpio_cfg_input(UART_CB.pselrxd, NRF_GPIO_PIN_NOPULL);
+    }
+
+    if (UART_CB.initialized) {
+        // For already initialized peripheral it is sufficient to reconfigure
+        // RX/TX pins only.
+
+        // Ensure that there is no unfinished TX transfer.
+        while (!serial_writable(obj)) {
+        }
+        // UART pins can be configured only when the peripheral is disabled.
+        nrf_uart_disable(UART_INSTANCE);
+        nrf_uart_txrx_pins_set(UART_INSTANCE, UART_CB.pseltxd, UART_CB.pselrxd);
+        nrf_uart_enable(UART_INSTANCE);
+    }
+    else {
+        UART_CB.baudrate = UART_DEFAULT_BAUDRATE;
+        UART_CB.parity   = UART_DEFAULT_PARITY;
+        UART_CB.hwfc     = UART_DEFAULT_HWFC;
+        UART_CB.pselcts  = UART_DEFAULT_CTS;
+        UART_CB.pselrts  = UART_DEFAULT_RTS;
+
+        nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_RXDRDY);
+        nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_TXDRDY);
+        nrf_uart_task_trigger(UART_INSTANCE, NRF_UART_TASK_STARTRX);
+        nrf_uart_task_trigger(UART_INSTANCE, NRF_UART_TASK_STARTTX);
+
+        nrf_uart_int_disable(UART_INSTANCE, NRF_UART_INT_MASK_RXDRDY |
+                                            NRF_UART_INT_MASK_TXDRDY);
+    #if DEVICE_SERIAL_ASYNCH
+        nrf_uart_int_enable(UART_INSTANCE, NRF_UART_INT_MASK_ERROR);
+    #endif
+        nrf_drv_common_irq_enable(UART_IRQn, APP_IRQ_PRIORITY_LOW);
+
+        // TX interrupt needs to be signaled when transmitter buffer is empty,
+        // so a dummy transmission is needed to get the TXDRDY event initially
+        // set.
+        nrf_uart_configure(UART_INSTANCE,
+            NRF_UART_PARITY_EXCLUDED, NRF_UART_HWFC_DISABLED);
+        // Use maximum baud rate, so this dummy transmission takes as little
+        // time as possible.
+        nrf_uart_baudrate_set(UART_INSTANCE, NRF_UART_BAUDRATE_1000000);
+        // Perform it with disconnected TX pin, so nothing actually comes out
+        // of the device.
+        nrf_uart_txrx_pins_disconnect(UART_INSTANCE);
+        nrf_uart_hwfc_pins_disconnect(UART_INSTANCE);
+        nrf_uart_enable(UART_INSTANCE);
+        nrf_uart_txd_set(UART_INSTANCE, 0);
+        while (!nrf_uart_event_check(UART_INSTANCE, NRF_UART_EVENT_TXDRDY)) {
+        }
+        nrf_uart_disable(UART_INSTANCE);
+
+        // Now everything is prepared to set the default configuration and
+        // connect the peripheral to actual pins.
+        nrf_uart_txrx_pins_set(UART_INSTANCE, UART_CB.pseltxd, UART_CB.pselrxd);
+        nrf_uart_baudrate_set(UART_INSTANCE, UART_CB.baudrate);
+        nrf_uart_configure(UART_INSTANCE, UART_CB.parity, UART_CB.hwfc);
+        if (UART_CB.hwfc == NRF_UART_HWFC_ENABLED) {
+            serial_set_flow_control(obj, FlowControlRTSCTS,
+                (PinName) UART_CB.pselrts, (PinName) UART_CB.pselcts);
+        }
+        nrf_uart_enable(UART_INSTANCE);
+
+        UART_CB.initialized = true;
+    }
+
+    if (tx == STDIO_UART_TX && rx == STDIO_UART_RX) {
+        stdio_uart_inited = 1;
+        memcpy(&stdio_uart, obj, sizeof(serial_t));
+    }
+    else {
+        stdio_uart_inited = 0;
+    }
+}
+
+void serial_free(serial_t *obj)
+{
+    (void)obj;
+
+    if (UART_CB.initialized) {
+        nrf_uart_disable(UART_INSTANCE);
+        nrf_uart_int_disable(UART_INSTANCE, NRF_UART_INT_MASK_RXDRDY |
+                                            NRF_UART_INT_MASK_TXDRDY |
+                                            NRF_UART_INT_MASK_ERROR);
+        nrf_drv_common_irq_disable(UART_IRQn);
+        UART_CB.initialized = false;
+
+        // There is only one UART instance, thus at this point the stdio UART
+        // can no longer be initialized.
+        stdio_uart_inited = 0;
+    }
+}
+
+void serial_baud(serial_t *obj, int baudrate)
+{
+    // nrf_uart_baudrate_set() is not used here (registers are accessed
+    // directly) to make it possible to set special baud rates like 56000
+    // or 31250.
+
+    static uint32_t const acceptedSpeeds[][2] = {
+        { 1200,    UART_BAUDRATE_BAUDRATE_Baud1200   },
+        { 2400,    UART_BAUDRATE_BAUDRATE_Baud2400   },
+        { 4800,    UART_BAUDRATE_BAUDRATE_Baud4800   },
+        { 9600,    UART_BAUDRATE_BAUDRATE_Baud9600   },
+        { 14400,   UART_BAUDRATE_BAUDRATE_Baud14400  },
+        { 19200,   UART_BAUDRATE_BAUDRATE_Baud19200  },
+        { 28800,   UART_BAUDRATE_BAUDRATE_Baud28800  },
+        { 31250,   (0x00800000UL) /* 31250 baud */   },
+        { 38400,   UART_BAUDRATE_BAUDRATE_Baud38400  },
+        { 56000,   (0x00E51000UL) /* 56000 baud */   },
+        { 57600,   UART_BAUDRATE_BAUDRATE_Baud57600  },
+        { 76800,   UART_BAUDRATE_BAUDRATE_Baud76800  },
+        { 115200,  UART_BAUDRATE_BAUDRATE_Baud115200 },
+        { 230400,  UART_BAUDRATE_BAUDRATE_Baud230400 },
+        { 250000,  UART_BAUDRATE_BAUDRATE_Baud250000 },
+        { 460800,  UART_BAUDRATE_BAUDRATE_Baud460800 },
+        { 921600,  UART_BAUDRATE_BAUDRATE_Baud921600 },
+        { 1000000, UART_BAUDRATE_BAUDRATE_Baud1M     }
+    };
+
+    if (baudrate <= 1200) {
+        UART_INSTANCE->BAUDRATE = UART_BAUDRATE_BAUDRATE_Baud1200;
+        return;
+    }
+
+    int const item_cnt = sizeof(acceptedSpeeds)/sizeof(acceptedSpeeds[0]);
+    for (int i = 1; i < item_cnt; i++) {
+        if ((uint32_t)baudrate < acceptedSpeeds[i][0]) {
+            UART_INSTANCE->BAUDRATE = acceptedSpeeds[i - 1][1];
+            return;
+        }
+    }
+
+    UART_INSTANCE->BAUDRATE = UART_BAUDRATE_BAUDRATE_Baud1M;
+}
+
+void serial_format(serial_t *obj,
+                   int data_bits, SerialParity parity, int stop_bits)
+{
+    (void)obj;
+
+    if (data_bits != 8) {
+        error("UART supports only 8 data bits.\r\n");
+    }
+    if (stop_bits != 1) {
+        error("UART supports only 1 stop bits.\r\n");
+    }
+    if (parity == ParityNone) {
+        UART_CB.parity = NRF_UART_PARITY_EXCLUDED;
+    } else if (parity == ParityEven) {
+        UART_CB.parity = NRF_UART_PARITY_INCLUDED;
+    } else {
+        error("UART supports only even parity.\r\n");
+    }
+
+    // Reconfigure UART peripheral.
+    nrf_uart_configure(UART_INSTANCE, UART_CB.parity, UART_CB.hwfc);
+}
+
+void serial_irq_handler(serial_t *obj, uart_irq_handler handler, uint32_t id)
+{
+    (void)obj;
+    UART_CB.irq_handler = handler;
+    UART_CB.irq_context = id;
+}
+
+void serial_irq_set(serial_t *obj, SerialIrq irq, uint32_t enable)
+{
+    (void)obj;
+    if (enable) {
+        switch (irq) {
+            case RxIrq:
+            #if DEVICE_SERIAL_ASYNCH
+                UART_CB.irq_enabled |= UART_IRQ_RX;
+            #endif
+                nrf_uart_int_enable(UART_INSTANCE, NRF_UART_INT_MASK_RXDRDY);
+                break;
+
+            case TxIrq:
+            #if DEVICE_SERIAL_ASYNCH
+                UART_CB.irq_enabled |= UART_IRQ_TX;
+            #endif
+                nrf_uart_int_enable(UART_INSTANCE, NRF_UART_INT_MASK_TXDRDY);
+                break;
+        }
+    } else {
+        switch (irq) {
+            case RxIrq:
+            #if DEVICE_SERIAL_ASYNCH
+                UART_CB.irq_enabled &= ~UART_IRQ_RX;
+                if (!UART_CB.rx_active)
+            #endif
+                {
+                    nrf_uart_int_disable(UART_INSTANCE,
+                        NRF_UART_INT_MASK_RXDRDY);
+                }
+                break;
+
+            case TxIrq:
+            #if DEVICE_SERIAL_ASYNCH
+                UART_CB.irq_enabled &= ~UART_IRQ_TX;
+                if (!UART_CB.tx_active)
+            #endif
+                {
+                    nrf_uart_int_disable(UART_INSTANCE,
+                        NRF_UART_INT_MASK_TXDRDY);
+                }
+                break;
+        }
+    }
+}
+
+int serial_getc(serial_t *obj)
+{
+    while (!serial_readable(obj)) {
+    }
+
+    nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_RXDRDY);
+    return nrf_uart_rxd_get(UART_INSTANCE);
+}
+
+void serial_putc(serial_t *obj, int c)
+{
+    while (!serial_writable(obj)) {
+    }
+
+    nrf_uart_event_clear(UART_INSTANCE, NRF_UART_EVENT_TXDRDY);
+    nrf_uart_txd_set(UART_INSTANCE, (uint8_t)c);
+}
+
+int serial_readable(serial_t *obj)
+{
+    (void)obj;
+#if DEVICE_SERIAL_ASYNCH
+    if (UART_CB.rx_active) {
+        return 0;
+    }
+#endif
+    return (nrf_uart_event_check(UART_INSTANCE, NRF_UART_EVENT_RXDRDY));
+}
+
+int serial_writable(serial_t *obj)
+{
+    (void)obj;
+#if DEVICE_SERIAL_ASYNCH
+    if (UART_CB.tx_active) {
+        return 0;
+    }
+#endif
+    return (nrf_uart_event_check(UART_INSTANCE, NRF_UART_EVENT_TXDRDY));
+}
+
+void serial_break_set(serial_t *obj)
+{
+    (void)obj;
+    nrf_uart_task_trigger(UART_INSTANCE, NRF_UART_TASK_SUSPEND);
+    nrf_uart_txrx_pins_disconnect(UART_INSTANCE);
+    nrf_gpio_pin_clear(UART_CB.pseltxd);
+}
+
+void serial_break_clear(serial_t *obj)
+{
+    (void)obj;
+    nrf_gpio_pin_set(UART_CB.pseltxd);
+    nrf_uart_txrx_pins_set(UART_INSTANCE, UART_CB.pseltxd, UART_CB.pselrxd);
+    nrf_uart_task_trigger(UART_INSTANCE, NRF_UART_TASK_STARTRX);
+    nrf_uart_task_trigger(UART_INSTANCE, NRF_UART_TASK_STARTTX);
+}
+
+void serial_set_flow_control(serial_t *obj, FlowControl type,
+                             PinName rxflow, PinName txflow)
+{
+    (void)obj;
+
+    UART_CB.pselrts =
+        (rxflow == NC) ? NRF_UART_PSEL_DISCONNECTED : (uint32_t)rxflow;
+    UART_CB.pselcts =
+        (txflow == NC) ? NRF_UART_PSEL_DISCONNECTED : (uint32_t)txflow;
+
+    if (UART_CB.pselrts != NRF_UART_PSEL_DISCONNECTED) {
+        nrf_gpio_pin_set(UART_CB.pselrts);
+        nrf_gpio_cfg_output(UART_CB.pselrts);
+    }
+    if (UART_CB.pselcts != NRF_UART_PSEL_DISCONNECTED) {
+        nrf_gpio_cfg_input(UART_CB.pselcts, NRF_GPIO_PIN_NOPULL);
+    }
+    nrf_uart_disable(UART_INSTANCE);
+    nrf_uart_hwfc_pins_set(UART_INSTANCE, UART_CB.pselrts, UART_CB.pselcts);
+    nrf_uart_enable(UART_INSTANCE);
+}
+
+void serial_clear(serial_t *obj) {
+    (void)obj;
+}
+
+#if DEVICE_SERIAL_ASYNCH
+
+int serial_tx_asynch(serial_t *obj, const void *tx, size_t tx_length,
+                     uint8_t tx_width, uint32_t handler, uint32_t event,
+                     DMAUsage hint)
+{
+    (void)obj;
+    (void)tx_width;
+    (void)hint;
+    if (UART_CB.tx_active || !tx_length) {
+        return 0;
+    }
+
+    UART_CB.tx_buffer = tx;
+    UART_CB.tx_length = tx_length;
+    UART_CB.tx_pos    = 0;
+    UART_CB.tx_asynch_handler = (void(*)())handler;
+    UART_CB.events_wanted &= ~SERIAL_EVENT_TX_ALL;
+    UART_CB.events_wanted |= event;
+
+    UART_CB.tx_active = true;
+    nrf_uart_int_enable(UART_INSTANCE, NRF_UART_INT_MASK_TXDRDY);
+
+    return 0;
+}
+
+void serial_rx_asynch(serial_t *obj, void *rx, size_t rx_length,
+                      uint8_t rx_width, uint32_t handler, uint32_t event,
+                      uint8_t char_match, DMAUsage hint)
+{
+    (void)obj;
+    (void)rx_width;
+    (void)hint;
+    if (UART_CB.rx_active || !rx_length) {
+        return;
+    }
+
+    UART_CB.rx_buffer = rx;
+    UART_CB.rx_length = rx_length;
+    UART_CB.rx_pos    = 0;
+    UART_CB.rx_asynch_handler = (void(*)())handler;
+    UART_CB.events_wanted &= ~SERIAL_EVENT_RX_ALL;
+    UART_CB.events_wanted |= event;
+    UART_CB.char_match = char_match;
+
+    UART_CB.rx_active = true;
+    nrf_uart_int_enable(UART_INSTANCE, NRF_UART_INT_MASK_RXDRDY);
+}
+
+uint8_t serial_tx_active(serial_t *obj)
+{
+    (void)obj;
+    return UART_CB.tx_active;
+}
+
+uint8_t serial_rx_active(serial_t *obj)
+{
+    (void)obj;
+    return UART_CB.rx_active;
+}
+
+int serial_irq_handler_asynch(serial_t *obj)
+{
+    (void)obj;
+    uint32_t events_to_report = UART_CB.events_wanted & UART_CB.events_occured;
+    UART_CB.events_occured &= (~events_to_report);
+    return events_to_report;
+}
+
+void serial_tx_abort_asynch(serial_t *obj)
+{
+    (void)obj;
+    end_asynch_tx();
+    UART_CB.tx_asynch_handler = NULL;
+}
+
+void serial_rx_abort_asynch(serial_t *obj)
+{
+    (void)obj;
+    end_asynch_rx();
+    UART_CB.rx_asynch_handler = NULL;
+}
+
+#endif // DEVICE_SERIAL_ASYNCH
+
+#endif // DEVICE_SERIAL