mbed library sources. Supersedes mbed-src.

Fork of mbed-dev by mbed official

Revision:
153:9398a535854b
Parent:
152:9a67f0b066fc
--- a/targets/TARGET_NUVOTON/TARGET_NUC472/serial_api.c	Thu Dec 15 11:48:27 2016 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,1117 +0,0 @@
-/* mbed Microcontroller Library
- * Copyright (c) 2015-2016 Nuvoton
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "serial_api.h"
-
-#if DEVICE_SERIAL
-
-#include "cmsis.h"
-#include "mbed_error.h"
-#include "mbed_assert.h"
-#include "PeripheralPins.h"
-#include "nu_modutil.h"
-#include "nu_bitutil.h"
-
-#if DEVICE_SERIAL_ASYNCH
-#include "dma_api.h"
-#include "dma.h"
-#endif
-
-struct nu_uart_var {
-    uint32_t    ref_cnt;                // Reference count of the H/W module
-    serial_t *  obj;
-    uint32_t    fifo_size_tx;
-    uint32_t    fifo_size_rx;
-    void        (*vec)(void);
-#if DEVICE_SERIAL_ASYNCH
-    void        (*vec_async)(void);
-    uint8_t     pdma_perp_tx;
-    uint8_t     pdma_perp_rx;
-#endif
-};
-
-static void uart0_vec(void);
-static void uart1_vec(void);
-static void uart2_vec(void);
-static void uart3_vec(void);
-static void uart4_vec(void);
-static void uart5_vec(void);
-static void uart_irq(serial_t *obj);
-
-#if DEVICE_SERIAL_ASYNCH
-static void uart0_vec_async(void);
-static void uart1_vec_async(void);
-static void uart2_vec_async(void);
-static void uart3_vec_async(void);
-static void uart4_vec_async(void);
-static void uart5_vec_async(void);
-static void uart_irq_async(serial_t *obj);
-
-static void uart_dma_handler_tx(uint32_t id, uint32_t event);
-static void uart_dma_handler_rx(uint32_t id, uint32_t event);
-
-static void serial_tx_enable_interrupt(serial_t *obj, uint32_t address, uint8_t enable);
-static void serial_rx_enable_interrupt(serial_t *obj, uint32_t address, uint8_t enable);
-static int serial_write_async(serial_t *obj);
-static int serial_read_async(serial_t *obj);
-
-static uint32_t serial_rx_event_check(serial_t *obj);
-static uint32_t serial_tx_event_check(serial_t *obj);
-
-static int serial_is_tx_complete(serial_t *obj);
-static void serial_tx_enable_event(serial_t *obj, int event, uint8_t enable);
-
-static void serial_tx_buffer_set(serial_t *obj, const void *tx, size_t length, uint8_t width);
-static void serial_rx_buffer_set(serial_t *obj, void *rx, size_t length, uint8_t width);
-static void serial_rx_set_char_match(serial_t *obj, uint8_t char_match);
-static void serial_rx_enable_event(serial_t *obj, int event, uint8_t enable);
-static int serial_is_rx_complete(serial_t *obj);
-
-static void serial_check_dma_usage(DMAUsage *dma_usage, int *dma_ch);
-static int serial_is_irq_en(serial_t *obj, SerialIrq irq);
-#endif
-
-static struct nu_uart_var uart0_var = {
-    .ref_cnt            =   0,
-    .obj                =   NULL,
-    .fifo_size_tx       =   64,
-    .fifo_size_rx       =   64,
-    .vec                =   uart0_vec,
-#if DEVICE_SERIAL_ASYNCH
-    .vec_async          =   uart0_vec_async,
-    .pdma_perp_tx       =   PDMA_UART0_TX,
-    .pdma_perp_rx       =   PDMA_UART0_RX
-#endif
-};
-static struct nu_uart_var uart1_var = {
-    .ref_cnt            =   0,
-    .obj                =   NULL,
-    .fifo_size_tx       =   16,
-    .fifo_size_rx       =   16,
-    .vec                =   uart1_vec,
-#if DEVICE_SERIAL_ASYNCH
-    .vec_async          =   uart1_vec_async,
-    .pdma_perp_tx       =   PDMA_UART1_TX,
-    .pdma_perp_rx       =   PDMA_UART1_RX
-#endif
-};
-static struct nu_uart_var uart2_var = {
-    .ref_cnt            =   0,
-    .obj                =   NULL,
-    .fifo_size_tx       =   16,
-    .fifo_size_rx       =   16,
-    .vec                =   uart2_vec,
-#if DEVICE_SERIAL_ASYNCH
-    .vec_async          =   uart2_vec_async,
-    .pdma_perp_tx       =   PDMA_UART2_TX,
-    .pdma_perp_rx       =   PDMA_UART2_RX
-#endif
-};
-static struct nu_uart_var uart3_var = {
-    .ref_cnt            =   0,
-    .obj                =   NULL,
-    .fifo_size_tx       =   16,
-    .fifo_size_rx       =   16,
-    .vec                =   uart3_vec,
-#if DEVICE_SERIAL_ASYNCH
-    .vec_async          =   uart3_vec_async,
-    .pdma_perp_tx       =   PDMA_UART3_TX,
-    .pdma_perp_rx       =   PDMA_UART3_RX
-#endif
-};
-static struct nu_uart_var uart4_var = {
-    .ref_cnt            =   0,
-    .obj                =   NULL,
-    .fifo_size_tx       =   16,
-    .fifo_size_rx       =   16,
-    .vec                =   uart4_vec,
-#if DEVICE_SERIAL_ASYNCH
-    .vec_async          =   uart4_vec_async,
-    .pdma_perp_tx       =   PDMA_UART4_TX,
-    .pdma_perp_rx       =   PDMA_UART4_RX
-#endif
-};
-static struct nu_uart_var uart5_var = {
-    .ref_cnt            =   0,
-    .obj                =   NULL,
-    .fifo_size_tx       =   16,
-    .fifo_size_rx       =   16,
-    .vec                =   uart5_vec,
-#if DEVICE_SERIAL_ASYNCH
-    .vec_async          =   uart5_vec_async,
-    .pdma_perp_tx       =   PDMA_UART5_TX,
-    .pdma_perp_rx       =   PDMA_UART5_RX
-#endif
-};
-
-
-int stdio_uart_inited = 0;
-serial_t stdio_uart;
-static uint32_t uart_modinit_mask = 0;
-
-static const struct nu_modinit_s uart_modinit_tab[] = {
-    {UART_0, UART0_MODULE, CLK_CLKSEL1_UARTSEL_HIRC, CLK_CLKDIV0_UART(1), UART0_RST, UART0_IRQn, &uart0_var},
-    {UART_1, UART1_MODULE, CLK_CLKSEL1_UARTSEL_HIRC, CLK_CLKDIV0_UART(1), UART1_RST, UART1_IRQn, &uart1_var},
-    {UART_2, UART2_MODULE, CLK_CLKSEL1_UARTSEL_HIRC, CLK_CLKDIV0_UART(1), UART2_RST, UART2_IRQn, &uart2_var},
-    {UART_3, UART3_MODULE, CLK_CLKSEL1_UARTSEL_HIRC, CLK_CLKDIV0_UART(1), UART3_RST, UART3_IRQn, &uart3_var},
-    {UART_4, UART4_MODULE, CLK_CLKSEL1_UARTSEL_HIRC, CLK_CLKDIV0_UART(1), UART4_RST, UART4_IRQn, &uart4_var},
-    {UART_5, UART5_MODULE, CLK_CLKSEL1_UARTSEL_HIRC, CLK_CLKDIV0_UART(1), UART5_RST, UART5_IRQn, &uart5_var},
-    
-    {NC, 0, 0, 0, 0, (IRQn_Type) 0, NULL}
-};
-
-extern void mbed_sdk_init(void);
-
-void serial_init(serial_t *obj, PinName tx, PinName rx)
-{
-    // NOTE: With armcc, serial_init() gets called from _sys_open() timing of which is before main()/mbed_sdk_init().
-    mbed_sdk_init();
-    
-    // Determine which UART_x the pins are used for
-    uint32_t uart_tx = pinmap_peripheral(tx, PinMap_UART_TX);
-    uint32_t uart_rx = pinmap_peripheral(rx, PinMap_UART_RX);
-    // Get the peripheral name (UART_x) from the pins and assign it to the object
-    obj->serial.uart = (UARTName) pinmap_merge(uart_tx, uart_rx);
-    MBED_ASSERT((int)obj->serial.uart != NC);
-
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    struct nu_uart_var *var = (struct nu_uart_var *) modinit->var;
-    
-    if (! var->ref_cnt) {
-        // Reset this module
-        SYS_ResetModule(modinit->rsetidx);
-    
-        // Select IP clock source
-        CLK_SetModuleClock(modinit->clkidx, modinit->clksrc, modinit->clkdiv);
-        // Enable IP clock
-        CLK_EnableModuleClock(modinit->clkidx);
-
-        pinmap_pinout(tx, PinMap_UART_TX);
-        pinmap_pinout(rx, PinMap_UART_RX);
-    
-        obj->serial.pin_tx = tx;
-        obj->serial.pin_rx = rx;
-    }
-    var->ref_cnt ++;
-    
-    // Configure the UART module and set its baudrate
-    serial_baud(obj, 9600);
-    // Configure data bits, parity, and stop bits
-    serial_format(obj, 8, ParityNone, 1);
-    
-    obj->serial.vec = var->vec;
-    
-#if DEVICE_SERIAL_ASYNCH
-    obj->serial.dma_usage_tx = DMA_USAGE_NEVER;
-    obj->serial.dma_usage_rx = DMA_USAGE_NEVER;
-    obj->serial.event = 0;
-    obj->serial.dma_chn_id_tx = DMA_ERROR_OUT_OF_CHANNELS;
-    obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
-#endif
-
-    // For stdio management
-    if (obj->serial.uart == STDIO_UART) {
-        stdio_uart_inited = 1;
-        memcpy(&stdio_uart, obj, sizeof(serial_t));
-    }
-    
-    if (var->ref_cnt) {
-        // Mark this module to be inited.
-        int i = modinit - uart_modinit_tab;
-        uart_modinit_mask |= 1 << i;
-    }
-}
-
-void serial_free(serial_t *obj)
-{
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    struct nu_uart_var *var = (struct nu_uart_var *) modinit->var;
-    
-    var->ref_cnt --;
-    if (! var->ref_cnt) {
-#if DEVICE_SERIAL_ASYNCH
-        if (obj->serial.dma_chn_id_tx != DMA_ERROR_OUT_OF_CHANNELS) {
-            dma_channel_free(obj->serial.dma_chn_id_tx);
-            obj->serial.dma_chn_id_tx = DMA_ERROR_OUT_OF_CHANNELS;
-        }
-        if (obj->serial.dma_chn_id_rx != DMA_ERROR_OUT_OF_CHANNELS) {
-            dma_channel_free(obj->serial.dma_chn_id_rx);
-            obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
-        }
-#endif
-
-        UART_Close((UART_T *) NU_MODBASE(obj->serial.uart));
-    
-        UART_DISABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), (UART_INTEN_RDAIEN_Msk | UART_INTEN_THREIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-        NVIC_DisableIRQ(modinit->irq_n);
-    
-        // Disable IP clock
-        CLK_DisableModuleClock(modinit->clkidx);
-    }
-    
-    if (var->obj == obj) {
-        var->obj = NULL;
-    }
-    
-    if (obj->serial.uart == STDIO_UART) {
-        stdio_uart_inited = 0;
-    }
-    
-    if (! var->ref_cnt) {
-        // Mark this module to be deinited.
-        int i = modinit - uart_modinit_tab;
-        uart_modinit_mask &= ~(1 << i);
-    }
-}
-
-void serial_baud(serial_t *obj, int baudrate) {
-    // Flush Tx FIFO. Otherwise, output data may get lost on this change.
-    while (! UART_IS_TX_EMPTY(((UART_T *) obj->serial.uart)));
-    
-    obj->serial.baudrate = baudrate;
-    UART_Open((UART_T *) NU_MODBASE(obj->serial.uart), baudrate);
-}
-
-void serial_format(serial_t *obj, int data_bits, SerialParity parity, int stop_bits) {
-    // Flush Tx FIFO. Otherwise, output data may get lost on this change.
-    while (! UART_IS_TX_EMPTY(((UART_T *) obj->serial.uart)));
-    
-    // TODO: Assert for not supported parity and data bits
-    obj->serial.databits = data_bits;
-    obj->serial.parity = parity;
-    obj->serial.stopbits = stop_bits;
-    
-    uint32_t databits_intern = (data_bits == 5) ? UART_WORD_LEN_5 :
-        (data_bits == 6) ? UART_WORD_LEN_6 :
-        (data_bits == 7) ? UART_WORD_LEN_7 : 
-        UART_WORD_LEN_8;
-    uint32_t parity_intern = (parity == ParityOdd || parity == ParityForced1) ? UART_PARITY_ODD :
-        (parity == ParityEven || parity == ParityForced0) ? UART_PARITY_EVEN :
-        UART_PARITY_NONE;
-    uint32_t stopbits_intern = (stop_bits == 2) ? UART_STOP_BIT_2 : UART_STOP_BIT_1;
-    UART_SetLine_Config((UART_T *) NU_MODBASE(obj->serial.uart), 
-        0,  // Don't change baudrate 
-        databits_intern, 
-        parity_intern, 
-        stopbits_intern);
-}
-
-#if DEVICE_SERIAL_FC
-
-void serial_set_flow_control(serial_t *obj, FlowControl type, PinName rxflow, PinName txflow)
-{
-    UART_T *uart_base = (UART_T *) NU_MODBASE(obj->serial.uart);
-    
-    // First, disable flow control completely.
-    uart_base->INTEN &= ~(UART_INTEN_ATORTSEN_Msk | UART_INTEN_ATOCTSEN_Msk);
-
-    if ((type == FlowControlRTS || type == FlowControlRTSCTS) && rxflow != NC) {
-        // Check if RTS pin matches.
-        uint32_t uart_rts = pinmap_peripheral(rxflow, PinMap_UART_RTS);
-        MBED_ASSERT(uart_rts == obj->serial.uart);
-        // Enable the pin for RTS function
-        pinmap_pinout(rxflow, PinMap_UART_RTS);
-        // nRTS pin output is high level active
-        uart_base->MODEM = (uart_base->MODEM & ~UART_MODEM_RTSACTLV_Msk) | UART_MODEM_RTSACTLV_Msk;
-        uart_base->FIFO = (uart_base->FIFO & ~UART_FIFO_RTSTRGLV_Msk) | UART_FIFO_RTSTRGLV_8BYTES;
-        // Enable RTS
-        uart_base->INTEN |= UART_INTEN_ATORTSEN_Msk;
-    }
-    
-    if ((type == FlowControlCTS || type == FlowControlRTSCTS) && txflow != NC)  {
-        // Check if CTS pin matches.
-        uint32_t uart_cts = pinmap_peripheral(txflow, PinMap_UART_CTS);
-        MBED_ASSERT(uart_cts == obj->serial.uart);
-        // Enable the pin for CTS function
-        pinmap_pinout(txflow, PinMap_UART_CTS);
-        // nCTS pin input is high level active
-        uart_base->MODEMSTS = (uart_base->MODEMSTS & ~UART_MODEMSTS_CTSACTLV_Msk) | UART_MODEMSTS_CTSACTLV_Msk;
-        // Enable CTS
-        uart_base->INTEN |= UART_INTEN_ATOCTSEN_Msk;
-    }
-}
-
-#endif  //DEVICE_SERIAL_FC
-
-void serial_irq_handler(serial_t *obj, uart_irq_handler handler, uint32_t id)
-{
-    // Flush Tx FIFO. Otherwise, output data may get lost on this change.
-    while (! UART_IS_TX_EMPTY(((UART_T *) obj->serial.uart)));
-    
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    obj->serial.irq_handler = (uint32_t) handler;
-    obj->serial.irq_id = id;
-    
-    // Restore sync-mode vector
-    obj->serial.vec = ((struct nu_uart_var *) modinit->var)->vec;
-}
-
-void serial_irq_set(serial_t *obj, SerialIrq irq, uint32_t enable)
-{
-    if (enable) {
-        const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-        MBED_ASSERT(modinit != NULL);
-        MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-        NVIC_SetVector(modinit->irq_n, (uint32_t) obj->serial.vec);
-        NVIC_EnableIRQ(modinit->irq_n);
-        
-        struct nu_uart_var *var = (struct nu_uart_var *) modinit->var;
-        // Multiple serial S/W objects for single UART H/W module possibly.
-        // Bind serial S/W object to UART H/W module as interrupt is enabled.
-        var->obj = obj;
-        
-        switch (irq) {
-            // NOTE: Setting inten_msk first to avoid race condition
-            case RxIrq:
-                obj->serial.inten_msk = obj->serial.inten_msk | (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk);
-                UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-                break;
-            case TxIrq:
-                obj->serial.inten_msk = obj->serial.inten_msk | UART_INTEN_THREIEN_Msk;
-                UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_THREIEN_Msk);
-                break;
-        }
-    } else { // disable
-        switch (irq) {
-            case RxIrq:
-                UART_DISABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-                obj->serial.inten_msk = obj->serial.inten_msk & ~(UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk);
-                break;
-            case TxIrq:
-                UART_DISABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_THREIEN_Msk);
-                obj->serial.inten_msk = obj->serial.inten_msk & ~UART_INTEN_THREIEN_Msk;
-                break;
-        }
-    }
-}
-
-int serial_getc(serial_t *obj)
-{
-    // TODO: Fix every byte access requires accompaniness of one interrupt. This degrades performance much.    
-    while (! serial_readable(obj));
-    int c = UART_READ(((UART_T *) NU_MODBASE(obj->serial.uart)));
-    
-    // Simulate clear of the interrupt flag
-    if (obj->serial.inten_msk & (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk)) {
-        UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-    }
-    
-    return c;
-}
-
-void serial_putc(serial_t *obj, int c)
-{
-    // TODO: Fix every byte access requires accompaniness of one interrupt. This degrades performance much.
-    while (! serial_writable(obj));
-    UART_WRITE(((UART_T *) NU_MODBASE(obj->serial.uart)), c);
-    
-    // Simulate clear of the interrupt flag
-    if (obj->serial.inten_msk & UART_INTEN_THREIEN_Msk) {
-        UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_THREIEN_Msk);
-    }
-}
-
-int serial_readable(serial_t *obj)
-{
-    //return UART_IS_RX_READY(((UART_T *) NU_MODBASE(obj->serial.uart)));
-    return ! (((UART_T *) NU_MODBASE(obj->serial.uart))->FIFOSTS & UART_FIFOSTS_RXEMPTY_Msk);
-}
-
-int serial_writable(serial_t *obj)
-{
-    return ! UART_IS_TX_FULL(((UART_T *) NU_MODBASE(obj->serial.uart)));
-}
-
-void serial_pinout_tx(PinName tx)
-{
-    pinmap_pinout(tx, PinMap_UART_TX);
-}
-
-void serial_break_set(serial_t *obj)
-{
-    ((UART_T *) NU_MODBASE(obj->serial.uart))->LINE |= UART_LINE_BCB_Msk;
-}
-
-void serial_break_clear(serial_t *obj)
-{
-    ((UART_T *) NU_MODBASE(obj->serial.uart))->LINE &= ~UART_LINE_BCB_Msk;
-}
-
-static void uart0_vec(void)
-{
-    uart_irq(uart0_var.obj);
-}
-
-static void uart1_vec(void)
-{
-    uart_irq(uart1_var.obj);
-}
-
-static void uart2_vec(void)
-{
-    uart_irq(uart2_var.obj);
-}
-
-static void uart3_vec(void)
-{
-    uart_irq(uart3_var.obj);
-}
-
-static void uart4_vec(void)
-{
-    uart_irq(uart4_var.obj);
-}
-
-static void uart5_vec(void)
-{
-    uart_irq(uart5_var.obj);
-}
-
-static void uart_irq(serial_t *obj)
-{
-    UART_T *uart_base = (UART_T *) NU_MODBASE(obj->serial.uart);
-
-    if (uart_base->INTSTS & (UART_INTSTS_RDAINT_Msk | UART_INTSTS_RXTOINT_Msk)) {
-        // Simulate clear of the interrupt flag. Temporarily disable the interrupt here and to be recovered on next read.
-        UART_DISABLE_INT(uart_base, (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-        if (obj->serial.irq_handler) {
-            ((uart_irq_handler) obj->serial.irq_handler)(obj->serial.irq_id, RxIrq);
-        }
-    }
-    
-    if (uart_base->INTSTS & UART_INTSTS_THREINT_Msk) {
-        // Simulate clear of the interrupt flag. Temporarily disable the interrupt here and to be recovered on next write.
-        UART_DISABLE_INT(uart_base, UART_INTEN_THREIEN_Msk);
-        if (obj->serial.irq_handler) {
-            ((uart_irq_handler) obj->serial.irq_handler)(obj->serial.irq_id, TxIrq);
-        }
-    }
-    
-    // FIXME: Ignore all other interrupt flags. Clear them. Otherwise, program will get stuck in interrupt.
-    uart_base->INTSTS = uart_base->INTSTS;
-    uart_base->FIFOSTS = uart_base->FIFOSTS;
-}
-
-
-#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)
-{
-    // NOTE: tx_width is deprecated. Assume its value is databits ceiled to the nearest number among 8, 16, and 32.
-    tx_width = (obj->serial.databits <= 8) ? 8 : (obj->serial.databits <= 16) ? 16 : 32;
-    
-    MBED_ASSERT(tx_width == 8 || tx_width == 16 || tx_width == 32);
-
-    obj->serial.dma_usage_tx = hint;
-    serial_check_dma_usage(&obj->serial.dma_usage_tx, &obj->serial.dma_chn_id_tx);
-    
-    // UART IRQ is necessary for both interrupt way and DMA way
-    serial_tx_enable_event(obj, event, 1);
-    serial_tx_buffer_set(obj, tx, tx_length, tx_width);
-    //UART_HAL_DisableTransmitter(obj->serial.address);
-    //UART_HAL_FlushTxFifo(obj->serial.address);
-    //UART_HAL_EnableTransmitter(obj->serial.address);
-            
-    int n_word = 0;
-    if (obj->serial.dma_usage_tx == DMA_USAGE_NEVER) {
-        // Interrupt way
-        n_word = serial_write_async(obj);
-        serial_tx_enable_interrupt(obj, handler, 1);
-    } else {
-        // DMA way
-        const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-        MBED_ASSERT(modinit != NULL);
-        MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-        PDMA->CHCTL |= 1 << obj->serial.dma_chn_id_tx;  // Enable this DMA channel
-        PDMA_SetTransferMode(obj->serial.dma_chn_id_tx,
-            ((struct nu_uart_var *) modinit->var)->pdma_perp_tx,    // Peripheral connected to this PDMA
-            0,  // Scatter-gather disabled
-            0); // Scatter-gather descriptor address
-        PDMA_SetTransferCnt(obj->serial.dma_chn_id_tx, 
-            (tx_width == 8) ? PDMA_WIDTH_8 : (tx_width == 16) ? PDMA_WIDTH_16 : PDMA_WIDTH_32, 
-            tx_length);
-        PDMA_SetTransferAddr(obj->serial.dma_chn_id_tx, 
-            ((uint32_t) tx) + (tx_width / 8) * tx_length,   // NOTE: End of source address
-            PDMA_SAR_INC,   // Source address incremental
-            (uint32_t) obj->serial.uart,    // Destination address
-            PDMA_DAR_FIX);  // Destination address fixed
-        PDMA_SetBurstType(obj->serial.dma_chn_id_tx, 
-            PDMA_REQ_SINGLE,    // Single mode
-            0); // Burst size
-        PDMA_EnableInt(obj->serial.dma_chn_id_tx,
-            0); // Interrupt type. No use here
-        // Register DMA event handler
-        dma_set_handler(obj->serial.dma_chn_id_tx, (uint32_t) uart_dma_handler_tx, (uint32_t) obj, DMA_EVENT_ALL);
-        serial_tx_enable_interrupt(obj, handler, 1);
-        ((UART_T *) NU_MODBASE(obj->serial.uart))->INTEN |= UART_INTEN_TXPDMAEN_Msk;  // Start DMA transfer
-    }
-    
-    return n_word;
-}
-
-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)
-{
-    // NOTE: rx_width is deprecated. Assume its value is databits ceiled to the nearest number among 8, 16, and 32.
-    rx_width = (obj->serial.databits <= 8) ? 8 : (obj->serial.databits <= 16) ? 16 : 32;
-    
-    MBED_ASSERT(rx_width == 8 || rx_width == 16 || rx_width == 32);
-
-    obj->serial.dma_usage_rx = hint;
-    serial_check_dma_usage(&obj->serial.dma_usage_rx, &obj->serial.dma_chn_id_rx);
-    // DMA doesn't support char match, so fall back to IRQ if it is requested.
-    if (obj->serial.dma_usage_rx != DMA_USAGE_NEVER && 
-        (event & SERIAL_EVENT_RX_CHARACTER_MATCH) && 
-        char_match != SERIAL_RESERVED_CHAR_MATCH) {
-        obj->serial.dma_usage_rx = DMA_USAGE_NEVER;
-        dma_channel_free(obj->serial.dma_chn_id_rx);
-        obj->serial.dma_chn_id_rx = DMA_ERROR_OUT_OF_CHANNELS;
-    }
-    
-    // UART IRQ is necessary for both interrupt way and DMA way
-    serial_rx_enable_event(obj, event, 1);
-    serial_rx_buffer_set(obj, rx, rx_length, rx_width);
-    serial_rx_set_char_match(obj, char_match);
-    //UART_HAL_DisableReceiver(obj->serial.address);
-    //UART_HAL_FlushRxFifo(obj->serial.address);
-    //UART_HAL_EnableReceiver(obj->serial.address);
-        
-    if (obj->serial.dma_usage_rx == DMA_USAGE_NEVER) {
-        // Interrupt way
-        serial_rx_enable_interrupt(obj, handler, 1);
-    } else {
-        // DMA way
-        const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-        MBED_ASSERT(modinit != NULL);
-        MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-        PDMA->CHCTL |= 1 << obj->serial.dma_chn_id_rx;  // Enable this DMA channel
-        PDMA_SetTransferMode(obj->serial.dma_chn_id_rx,
-            ((struct nu_uart_var *) modinit->var)->pdma_perp_rx,    // Peripheral connected to this PDMA
-            0,  // Scatter-gather disabled
-            0); // Scatter-gather descriptor address
-        PDMA_SetTransferCnt(obj->serial.dma_chn_id_rx, 
-            (rx_width == 8) ? PDMA_WIDTH_8 : (rx_width == 16) ? PDMA_WIDTH_16 : PDMA_WIDTH_32, 
-            rx_length);
-        PDMA_SetTransferAddr(obj->serial.dma_chn_id_rx,
-            (uint32_t) obj->serial.uart,    // Source address
-            PDMA_SAR_FIX,   // Source address fixed
-            ((uint32_t) rx) + (rx_width / 8) * rx_length,   // NOTE: End of destination address
-            PDMA_DAR_INC);  // Destination address incremental
-        PDMA_SetBurstType(obj->serial.dma_chn_id_rx, 
-            PDMA_REQ_SINGLE,    // Single mode
-            0); // Burst size
-        PDMA_EnableInt(obj->serial.dma_chn_id_rx,
-            0); // Interrupt type. No use here
-        // Register DMA event handler
-        dma_set_handler(obj->serial.dma_chn_id_rx, (uint32_t) uart_dma_handler_rx, (uint32_t) obj, DMA_EVENT_ALL);
-        serial_rx_enable_interrupt(obj, handler, 1);
-        ((UART_T *) NU_MODBASE(obj->serial.uart))->INTEN |= UART_INTEN_RXPDMAEN_Msk;  // Start DMA transfer
-    }
-}
-
-void serial_tx_abort_asynch(serial_t *obj)
-{
-    // Flush Tx FIFO. Otherwise, output data may get lost on this change.
-    while (! UART_IS_TX_EMPTY(((UART_T *) obj->serial.uart)));
-    
-    if (obj->serial.dma_usage_tx != DMA_USAGE_NEVER) {
-        if (obj->serial.dma_chn_id_tx != DMA_ERROR_OUT_OF_CHANNELS) {
-            PDMA_DisableInt(obj->serial.dma_chn_id_tx, 0);
-            // FIXME: Next PDMA transfer will fail with PDMA_STOP() called. Cause is unknown.
-            //PDMA_STOP(obj->serial.dma_chn_id_tx);
-            PDMA->CHCTL &= ~(1 << obj->serial.dma_chn_id_tx);
-        }
-        UART_DISABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_TXPDMAEN_Msk);
-    }
-    
-    // Necessary for both interrupt way and DMA way
-    serial_irq_set(obj, TxIrq, 0);
-    // FIXME: more complete abort operation
-    //UART_HAL_DisableTransmitter(obj->serial.serial.address);
-    //UART_HAL_FlushTxFifo(obj->serial.serial.address);
-}
-
-void serial_rx_abort_asynch(serial_t *obj)
-{
-    if (obj->serial.dma_usage_rx != DMA_USAGE_NEVER) {
-        if (obj->serial.dma_chn_id_rx != DMA_ERROR_OUT_OF_CHANNELS) {
-            PDMA_DisableInt(obj->serial.dma_chn_id_rx, 0);
-            // FIXME: Next PDMA transfer will fail with PDMA_STOP() called. Cause is unknown.
-            //PDMA_STOP(obj->serial.dma_chn_id_rx);
-            PDMA->CHCTL &= ~(1 << obj->serial.dma_chn_id_rx);
-        }
-        UART_DISABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_RXPDMAEN_Msk);
-    }
-    
-    // Necessary for both interrupt way and DMA way
-    serial_irq_set(obj, RxIrq, 0);
-    // FIXME: more complete abort operation
-    //UART_HAL_DisableReceiver(obj->serial.serial.address);
-    //UART_HAL_FlushRxFifo(obj->serial.serial.address);
-}
-
-uint8_t serial_tx_active(serial_t *obj)
-{
-    return serial_is_irq_en(obj, TxIrq);
-}
-
-uint8_t serial_rx_active(serial_t *obj)
-{
-    return serial_is_irq_en(obj, RxIrq);
-}
-
-int serial_irq_handler_asynch(serial_t *obj)
-{
-    int event_rx = 0;
-    int event_tx = 0;
-    
-    // Necessary for both interrupt way and DMA way
-    if (serial_is_irq_en(obj, RxIrq)) {
-        event_rx = serial_rx_event_check(obj);
-        if (event_rx) {
-            serial_rx_abort_asynch(obj);
-        }
-    }
-        
-    if (serial_is_irq_en(obj, TxIrq)) {
-        event_tx = serial_tx_event_check(obj);
-        if (event_tx) {
-            serial_tx_abort_asynch(obj);
-        }
-    }
-        
-    return (obj->serial.event & (event_rx | event_tx));
-}
-
-int serial_allow_powerdown(void)
-{
-    uint32_t modinit_mask = uart_modinit_mask;
-    while (modinit_mask) {
-        int uart_idx = nu_ctz(modinit_mask);
-        const struct nu_modinit_s *modinit = uart_modinit_tab + uart_idx;
-        if (modinit->modname != NC) {
-            UART_T *uart_base = (UART_T *) NU_MODBASE(modinit->modname);
-            // Disallow entering power-down mode if Tx FIFO has data to flush
-            if (! UART_IS_TX_EMPTY((uart_base))) {
-                return 0;
-            }
-            // Disallow entering power-down mode if async Rx transfer (not PDMA) is on-going
-            if (uart_base->INTEN & (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk)) {
-                return 0;
-            }
-            // Disallow entering power-down mode if async Rx transfer (PDMA) is on-going
-            if (uart_base->INTEN & UART_INTEN_RXPDMAEN_Msk) {
-                return 0;
-            }
-        }
-        modinit_mask &= ~(1 << uart_idx);
-    }
-    
-    return 1;
-}
-
-static void uart0_vec_async(void)
-{
-    uart_irq_async(uart0_var.obj);
-}
-
-static void uart1_vec_async(void)
-{
-    uart_irq_async(uart1_var.obj);
-}
-
-static void uart2_vec_async(void)
-{
-    uart_irq_async(uart2_var.obj);
-}
-
-static void uart3_vec_async(void)
-{
-    uart_irq_async(uart3_var.obj);
-}
-
-static void uart4_vec_async(void)
-{
-    uart_irq_async(uart4_var.obj);
-}
-
-static void uart5_vec_async(void)
-{
-    uart_irq_async(uart5_var.obj);
-}
-
-static void uart_irq_async(serial_t *obj)
-{
-    if (serial_is_irq_en(obj, RxIrq)) {
-        (*obj->serial.irq_handler_rx_async)();
-    }
-    if (serial_is_irq_en(obj, TxIrq)) {
-        (*obj->serial.irq_handler_tx_async)();
-    }
-}
-
-static void serial_rx_set_char_match(serial_t *obj, uint8_t char_match)
-{
-    obj->char_match = char_match;
-    obj->char_found = 0;
-}
-
-static void serial_tx_enable_event(serial_t *obj, int event, uint8_t enable)
-{
-    obj->serial.event &= ~SERIAL_EVENT_TX_MASK;
-    obj->serial.event |= (event & SERIAL_EVENT_TX_MASK);
-    
-    //if (event & SERIAL_EVENT_TX_COMPLETE) {
-    //}
-}
-
-static void serial_rx_enable_event(serial_t *obj, int event, uint8_t enable)
-{
-    obj->serial.event &= ~SERIAL_EVENT_RX_MASK;
-    obj->serial.event |= (event & SERIAL_EVENT_RX_MASK);
-    
-    //if (event & SERIAL_EVENT_RX_COMPLETE) {
-    //}
-    //if (event & SERIAL_EVENT_RX_OVERRUN_ERROR) {
-    //}
-    if (event & SERIAL_EVENT_RX_FRAMING_ERROR) {
-        UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_RLSIEN_Msk);
-    }
-    if (event & SERIAL_EVENT_RX_PARITY_ERROR) {
-        UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_RLSIEN_Msk);
-    }
-    if (event & SERIAL_EVENT_RX_OVERFLOW) {
-        UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_BUFERRIEN_Msk);
-    }
-    //if (event & SERIAL_EVENT_RX_CHARACTER_MATCH) {
-    //}
-}
-
-static int serial_is_tx_complete(serial_t *obj)
-{
-    // NOTE: Exclude tx fifo empty check due to no such interrupt on DMA way
-    //return (obj->tx_buff.pos == obj->tx_buff.length) && UART_GET_TX_EMPTY(((UART_T *) NU_MODBASE(obj->serial.uart)));
-    // FIXME: Premature abort???
-    return (obj->tx_buff.pos == obj->tx_buff.length);
-}
-
-static int serial_is_rx_complete(serial_t *obj)
-{
-    //return (obj->rx_buff.pos == obj->rx_buff.length) && UART_GET_RX_EMPTY(((UART_T *) NU_MODBASE(obj->serial.uart)));
-    return (obj->rx_buff.pos == obj->rx_buff.length);
-}
-
-static uint32_t serial_tx_event_check(serial_t *obj)
-{
-    UART_T *uart_base = (UART_T *) NU_MODBASE(obj->serial.uart);
-    
-    if (uart_base->INTSTS & UART_INTSTS_THREINT_Msk) {
-        // Simulate clear of the interrupt flag. Temporarily disable the interrupt here and to be recovered on next write.
-        UART_DISABLE_INT(uart_base, UART_INTEN_THREIEN_Msk);
-    }
-    
-    uint32_t event = 0;
-    
-    if (obj->serial.dma_usage_tx == DMA_USAGE_NEVER) {
-        serial_write_async(obj);
-    }
-    
-    if (serial_is_tx_complete(obj)) {
-        event |= SERIAL_EVENT_TX_COMPLETE;
-    }
-    
-    return event;
-}
-
-static uint32_t serial_rx_event_check(serial_t *obj)
-{
-    UART_T *uart_base = (UART_T *) NU_MODBASE(obj->serial.uart);
-    
-    if (uart_base->INTSTS & (UART_INTSTS_RDAINT_Msk | UART_INTSTS_RXTOINT_Msk)) {
-        // Simulate clear of the interrupt flag. Temporarily disable the interrupt here and to be recovered on next read.
-        UART_DISABLE_INT(uart_base, (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-    }
-    
-    uint32_t event = 0;
-    
-    if (uart_base->FIFOSTS & UART_FIFOSTS_BIF_Msk) {
-        uart_base->FIFOSTS = UART_FIFOSTS_BIF_Msk;
-    }
-    if (uart_base->FIFOSTS & UART_FIFOSTS_FEF_Msk) {
-        uart_base->FIFOSTS = UART_FIFOSTS_FEF_Msk;
-        event |= SERIAL_EVENT_RX_FRAMING_ERROR;
-    }
-    if (uart_base->FIFOSTS & UART_FIFOSTS_PEF_Msk) {
-        uart_base->FIFOSTS = UART_FIFOSTS_PEF_Msk;
-        event |= SERIAL_EVENT_RX_PARITY_ERROR;
-    }
-    
-    if (uart_base->FIFOSTS & UART_FIFOSTS_RXOVIF_Msk) {
-        uart_base->FIFOSTS = UART_FIFOSTS_RXOVIF_Msk;
-        event |= SERIAL_EVENT_RX_OVERFLOW;
-    }
-
-    if (obj->serial.dma_usage_rx == DMA_USAGE_NEVER) {
-        serial_read_async(obj);
-    }
-    
-    if (serial_is_rx_complete(obj)) {
-        event |= SERIAL_EVENT_RX_COMPLETE;
-    }
-    if ((obj->char_match != SERIAL_RESERVED_CHAR_MATCH) && obj->char_found) {
-        event |= SERIAL_EVENT_RX_CHARACTER_MATCH;
-        // FIXME: Timing to reset char_found?
-        //obj->char_found = 0;
-    }
-    
-    return event;
-}
-
-static void uart_dma_handler_tx(uint32_t id, uint32_t event_dma)
-{
-    serial_t *obj = (serial_t *) id;
-    
-    // FIXME: Pass this error to caller
-    if (event_dma & DMA_EVENT_ABORT) {
-    }
-    // Expect UART IRQ will catch this transfer done event
-    if (event_dma & DMA_EVENT_TRANSFER_DONE) {
-        obj->tx_buff.pos = obj->tx_buff.length;
-    }
-    // FIXME: Pass this error to caller
-    if (event_dma & DMA_EVENT_TIMEOUT) {
-    }
-    
-    uart_irq_async(obj);
-}
-
-static void uart_dma_handler_rx(uint32_t id, uint32_t event_dma)
-{
-    serial_t *obj = (serial_t *) id;
-    
-    // FIXME: Pass this error to caller
-    if (event_dma & DMA_EVENT_ABORT) {
-    }
-    // Expect UART IRQ will catch this transfer done event
-    if (event_dma & DMA_EVENT_TRANSFER_DONE) {
-        obj->rx_buff.pos = obj->rx_buff.length;
-    }
-    // FIXME: Pass this error to caller
-    if (event_dma & DMA_EVENT_TIMEOUT) {
-    }
-    
-    uart_irq_async(obj);
-}
-
-static int serial_write_async(serial_t *obj)
-{   
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    UART_T *uart_base = (UART_T *) NU_MODBASE(obj->serial.uart);
-    
-    uint32_t tx_fifo_max = ((struct nu_uart_var *) modinit->var)->fifo_size_tx;
-    uint32_t tx_fifo_busy = (uart_base->FIFOSTS & UART_FIFOSTS_TXPTR_Msk) >> UART_FIFOSTS_TXPTR_Pos;
-    if (uart_base->FIFOSTS & UART_FIFOSTS_TXFULL_Msk) {
-        tx_fifo_busy = tx_fifo_max;
-    }
-    uint32_t tx_fifo_free = tx_fifo_max - tx_fifo_busy;
-    if (tx_fifo_free == 0) {
-        // Simulate clear of the interrupt flag
-        if (obj->serial.inten_msk & UART_INTEN_THREIEN_Msk) {
-            UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_THREIEN_Msk);
-        }
-        return 0;
-    }
-    
-    uint32_t bytes_per_word = obj->tx_buff.width / 8;
-    
-    uint8_t *tx = (uint8_t *)(obj->tx_buff.buffer) + bytes_per_word * obj->tx_buff.pos;
-    int n_words = 0;
-    while (obj->tx_buff.pos < obj->tx_buff.length && tx_fifo_free >= bytes_per_word) {
-        switch (bytes_per_word) {
-            case 4:
-                UART_WRITE(((UART_T *) NU_MODBASE(obj->serial.uart)), *tx ++);
-                UART_WRITE(((UART_T *) NU_MODBASE(obj->serial.uart)), *tx ++);
-            case 2:
-                UART_WRITE(((UART_T *) NU_MODBASE(obj->serial.uart)), *tx ++);
-            case 1:
-                UART_WRITE(((UART_T *) NU_MODBASE(obj->serial.uart)), *tx ++);
-        }
-        
-        n_words ++;
-        tx_fifo_free -= bytes_per_word;
-        obj->tx_buff.pos ++;
-    }
-    
-    if (n_words) {
-        // Simulate clear of the interrupt flag
-        if (obj->serial.inten_msk & UART_INTEN_THREIEN_Msk) {
-            UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), UART_INTEN_THREIEN_Msk);
-        }
-    }
-    
-    return n_words;
-}
-
-static int serial_read_async(serial_t *obj)
-{
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    uint32_t rx_fifo_busy = (((UART_T *) NU_MODBASE(obj->serial.uart))->FIFOSTS & UART_FIFOSTS_RXPTR_Msk) >> UART_FIFOSTS_RXPTR_Pos;
-    //uint32_t rx_fifo_free = ((struct nu_uart_var *) modinit->var)->fifo_size_rx - rx_fifo_busy;
-    //if (rx_fifo_free == 0) {
-    //    return 0;
-    //}
-    
-    uint32_t bytes_per_word = obj->rx_buff.width / 8;
-    
-    uint8_t *rx = (uint8_t *)(obj->rx_buff.buffer) + bytes_per_word * obj->rx_buff.pos;
-    int n_words = 0;
-    while (obj->rx_buff.pos < obj->rx_buff.length && rx_fifo_busy >= bytes_per_word) {
-        switch (bytes_per_word) {
-            case 4:
-                *rx ++ = UART_READ(((UART_T *) NU_MODBASE(obj->serial.uart)));
-                *rx ++ = UART_READ(((UART_T *) NU_MODBASE(obj->serial.uart)));
-            case 2:
-                *rx ++ = UART_READ(((UART_T *) NU_MODBASE(obj->serial.uart)));
-            case 1:
-                *rx ++ = UART_READ(((UART_T *) NU_MODBASE(obj->serial.uart)));
-        }
-        
-        n_words ++;
-        rx_fifo_busy -= bytes_per_word;
-        obj->rx_buff.pos ++;
-        
-        if ((obj->serial.event & SERIAL_EVENT_RX_CHARACTER_MATCH) &&
-            obj->char_match != SERIAL_RESERVED_CHAR_MATCH) {
-            uint8_t *rx_cmp = rx;
-            switch (bytes_per_word) {
-                case 4:
-                    rx_cmp -= 2;
-                case 2:
-                    rx_cmp --;
-                case 1:
-                    rx_cmp --;
-            }
-            if (*rx_cmp == obj->char_match) {
-                obj->char_found = 1;
-                break;
-            }
-        }
-    }
-    
-    if (n_words) {
-        // Simulate clear of the interrupt flag
-        if (obj->serial.inten_msk & (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk)) {
-            UART_ENABLE_INT(((UART_T *) NU_MODBASE(obj->serial.uart)), (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk));
-        }
-    }
-    
-    return n_words;
-}
-
-static void serial_tx_buffer_set(serial_t *obj, const void *tx, size_t length, uint8_t width)
-{
-    obj->tx_buff.buffer = (void *) tx;
-    obj->tx_buff.length = length;
-    obj->tx_buff.pos = 0;
-    obj->tx_buff.width = width;
-}
-
-static void serial_rx_buffer_set(serial_t *obj, void *rx, size_t length, uint8_t width)
-{
-    obj->rx_buff.buffer = rx;
-    obj->rx_buff.length = length;
-    obj->rx_buff.pos = 0;
-    obj->rx_buff.width = width;
-}
-
-static void serial_tx_enable_interrupt(serial_t *obj, uint32_t handler, uint8_t enable)
-{
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    // Necessary for both interrupt way and DMA way
-    struct nu_uart_var *var = (struct nu_uart_var *) modinit->var;
-    // With our own async vector, tx/rx handlers can be different.
-    obj->serial.vec = var->vec_async;
-    obj->serial.irq_handler_tx_async = (void (*)(void)) handler;
-    serial_irq_set(obj, TxIrq, enable);
-}
-
-static void serial_rx_enable_interrupt(serial_t *obj, uint32_t handler, uint8_t enable)
-{
-    const struct nu_modinit_s *modinit = get_modinit(obj->serial.uart, uart_modinit_tab);
-    MBED_ASSERT(modinit != NULL);
-    MBED_ASSERT(modinit->modname == obj->serial.uart);
-    
-    // Necessary for both interrupt way and DMA way
-    struct nu_uart_var *var = (struct nu_uart_var *) modinit->var;
-    // With our own async vector, tx/rx handlers can be different.
-    obj->serial.vec = var->vec_async;
-    obj->serial.irq_handler_rx_async = (void (*) (void)) handler;
-    serial_irq_set(obj, RxIrq, enable);
-}
-
-static void serial_check_dma_usage(DMAUsage *dma_usage, int *dma_ch)
-{
-    if (*dma_usage != DMA_USAGE_NEVER) {
-        if (*dma_ch == DMA_ERROR_OUT_OF_CHANNELS) {
-            *dma_ch = dma_channel_allocate(DMA_CAP_NONE);
-        }
-        if (*dma_ch == DMA_ERROR_OUT_OF_CHANNELS) {
-            *dma_usage = DMA_USAGE_NEVER;
-        }
-    }
-    else {
-        dma_channel_free(*dma_ch);
-        *dma_ch = DMA_ERROR_OUT_OF_CHANNELS;
-    }
-}
-
-static int serial_is_irq_en(serial_t *obj, SerialIrq irq)
-{
-    int inten_msk = 0;
-    
-    switch (irq) {
-        case RxIrq:
-            inten_msk = obj->serial.inten_msk & (UART_INTEN_RDAIEN_Msk | UART_INTEN_RXTOIEN_Msk);
-            break;
-        case TxIrq:
-            inten_msk = obj->serial.inten_msk & UART_INTEN_THREIEN_Msk;
-            break;
-    }
-    
-    return !! inten_msk;
-}
-
-#endif  // #if DEVICE_SERIAL_ASYNCH
-#endif  // #if DEVICE_SERIAL