text: // Copyright 2015-2019 Espressif Systems (Shanghai) PTE LTD
  //
  // 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.
  
  // The LL layer for UART register operations.
  // Note that most of the register operations in this layer are non-atomic operations.
  
  
  #pragma once
  #include "hal/uart_types.h"
  #include "soc/uart_periph.h"
  
  // The default fifo depth
  #define UART_LL_FIFO_DEF_LEN  (UART_FIFO_LEN)
  // Get UART hardware instance with giving uart num
  #define UART_LL_GET_HW(num) (((num) == 0) ? (&UART0) : (&UART1))
  
  
  // Define UART interrupts
  typedef enum {
      UART_INTR_RXFIFO_FULL      = (0x1<<0),
      UART_INTR_TXFIFO_EMPTY     = (0x1<<1),
      UART_INTR_PARITY_ERR       = (0x1<<2),
      UART_INTR_FRAM_ERR         = (0x1<<3),
      UART_INTR_RXFIFO_OVF       = (0x1<<4),
      UART_INTR_DSR_CHG          = (0x1<<5),
      UART_INTR_CTS_CHG          = (0x1<<6),
      UART_INTR_BRK_DET          = (0x1<<7),
      UART_INTR_RXFIFO_TOUT      = (0x1<<8),
      UART_INTR_SW_XON           = (0x1<<9),
      UART_INTR_SW_XOFF          = (0x1<<10),
      UART_INTR_GLITCH_DET       = (0x1<<11),
      UART_INTR_TX_BRK_DONE      = (0x1<<12),
      UART_INTR_TX_BRK_IDLE      = (0x1<<13),
      UART_INTR_TX_DONE          = (0x1<<14),
      UART_INTR_RS485_PARITY_ERR = (0x1<<15),
      UART_INTR_RS485_FRM_ERR    = (0x1<<16),
      UART_INTR_RS485_CLASH      = (0x1<<17),
      UART_INTR_CMD_CHAR_DET     = (0x1<<18),
  } uart_intr_t;
  
  
  /**
   * @brief  Configure the baud-rate.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  baud The baud rate to be set. When the source clock is APB, the max baud rate is `UART_LL_BITRATE_MAX`
   * @param  source_clk The UART source clock. The source clock can be APB clock or REF_TICK.
   *                    If the source clock is REF_TICK, the UART can still work when the APB changes.
   *
   * @return None
   */
  static inline void uart_ll_set_baudrate(uart_dev_t *hw, uart_sclk_t source_clk, uint32_t baud)
  {
      uint32_t sclk_freq = (source_clk == UART_SCLK_APB) ? APB_CLK_FREQ : REF_CLK_FREQ;
      uint32_t clk_div = ((sclk_freq) << 4) / baud;
      // The baud rate configuration register is divided into
      // an integer part and a fractional part.
      hw->clk_div.div_int = clk_div >> 4;
      hw->clk_div.div_frag = clk_div &  0xf;
      // Configure the UART source clock.
      hw->conf0.tick_ref_always_on = (source_clk == UART_SCLK_APB);
  }
  
  /**
   * @brief  Get the current baud-rate.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return The current baudrate
   */
  static inline uint32_t uart_ll_get_baudrate(uart_dev_t *hw)
  {
      uint32_t src_clk = hw->conf0.tick_ref_always_on ? APB_CLK_FREQ : REF_CLK_FREQ;
      typeof(hw->clk_div) div_reg = hw->clk_div;
      return ((src_clk << 4)) / ((div_reg.div_int << 4) | div_reg.div_frag);
  }
  
  /**
   * @brief  Enable the UART interrupt based on the given mask.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  mask The bitmap of the interrupts need to be enabled.
   *
   * @return None
   */
  static inline void uart_ll_ena_intr_mask(uart_dev_t *hw, uint32_t mask)
  {
      hw->int_ena.val |= mask;
  }
  
  /**
   * @brief  Disable the UART interrupt based on the given mask.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  mask The bitmap of the interrupts need to be disabled.
   *
   * @return None
   */
  static inline void uart_ll_disable_intr_mask(uart_dev_t *hw, uint32_t mask)
  {
      hw->int_ena.val &= (~mask);
  }
  
  /**
   * @brief  Get the UART interrupt status.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return The UART interrupt status.
   */
  static inline uint32_t uart_ll_get_intsts_mask(uart_dev_t *hw)
  {
      return hw->int_st.val;
  }
  
  /**
   * @brief  Clear the UART interrupt status based on the given mask.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  mask The bitmap of the interrupts need to be cleared.
   *
   * @return None
   */
  static inline void uart_ll_clr_intsts_mask(uart_dev_t *hw, uint32_t mask)
  {
      hw->int_clr.val = mask;
  }
  
  /**
   * @brief  Read the UART rxfifo.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  buf The data buffer. The buffer size should be large than 128 byts.
   * @param  rd_len The data length needs to be read.
   *
   * @return None.
   */
  static inline void uart_ll_read_rxfifo(uart_dev_t *hw, uint8_t *buf, uint32_t rd_len)
  {
      //Get the UART fifo addr, ESP32-S2 have 2 UART
      uint32_t fifo_addr = (hw == &UART0) ? UART_FIFO_AHB_REG(0) : UART_FIFO_AHB_REG(1);
      for(int i = 0; i < rd_len; i++) {
          buf[i] = READ_PERI_REG(fifo_addr);
      }
  }
  
  /**
   * @brief  Write byte to the UART txfifo.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  buf The data buffer.
   * @param  wr_len The data length needs to be writen.
   *
   * @return None
   */
  static inline void uart_ll_write_txfifo(uart_dev_t *hw, const uint8_t *buf, uint32_t wr_len)
  {
      //Get the UART fifo addr, ESP32-S2 have 2 UART
      uint32_t fifo_addr = (hw == &UART0) ? UART_FIFO_AHB_REG(0) : UART_FIFO_AHB_REG(1);
      for(int i = 0; i < wr_len; i++) {
          WRITE_PERI_REG(fifo_addr, buf[i]);
      }
  }
  
  /**
   * @brief  Reset the UART hw rxfifo.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None
   */
  static inline void uart_ll_rxfifo_rst(uart_dev_t *hw)
  {
      hw->conf0.rxfifo_rst = 1;
      hw->conf0.rxfifo_rst = 0;
  }
  
  /**
   * @brief  Reset the UART hw txfifo.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None
   */
  static inline void uart_ll_txfifo_rst(uart_dev_t *hw)
  {
      hw->conf0.txfifo_rst = 1;
      hw->conf0.txfifo_rst = 0;
  }
  
  /**
   * @brief  Get the length of readable data in UART rxfifo.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return The readable data length in rxfifo.
   */
  static inline uint32_t uart_ll_get_rxfifo_len(uart_dev_t *hw)
  {
      return hw->status.rxfifo_cnt;
  }
  
  /**
   * @brief  Get the writable data length of UART txfifo.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return The data length of txfifo can be written.
   */
  static inline uint32_t uart_ll_get_txfifo_len(uart_dev_t *hw)
  {
      return UART_LL_FIFO_DEF_LEN - hw->status.txfifo_cnt;
  }
  
  /**
   * @brief  Configure the UART stop bit.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  stop_bit The stop bit number to be set.
   *
   * @return None.
   */
  static inline void uart_ll_set_stop_bits(uart_dev_t *hw, uart_stop_bits_t stop_bit)
  { 
      hw->conf0.stop_bit_num = stop_bit;
  }
  
  /**
   * @brief  Get the configuration of the UART stop bit.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  stop_bit The pointer to accept the stop bit configuration
   *
   * @return None.
   */
  static inline void uart_ll_get_stop_bits(uart_dev_t *hw, uart_stop_bits_t *stop_bit)
  {
      *stop_bit = hw->conf0.stop_bit_num;
  }
  
  /**
   * @brief  Configure the UART parity check mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  parity_mode The parity check mode to be set.
   *
   * @return None.
   */
  static inline void uart_ll_set_parity(uart_dev_t *hw, uart_parity_t parity_mode)
  {
      if(parity_mode != UART_PARITY_DISABLE) {
          hw->conf0.parity = parity_mode & 0x1;
      }
      hw->conf0.parity_en = (parity_mode >> 1) & 0x1;
  }
  
  /**
   * @brief  Get the UART parity check mode configuration.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  parity_mode The pointer to accept the parity check mode configuration.
   *
   * @return None.
   */
  static inline void uart_ll_get_parity(uart_dev_t *hw, uart_parity_t *parity_mode)
  {
      if(hw->conf0.parity_en) {
          *parity_mode = 0X2 | hw->conf0.parity;
      } else {
          *parity_mode = UART_PARITY_DISABLE;
      }
  }
  
  /**
   * @brief  Set the UART rxfifo full threshold value. When the data in rxfifo is more than the threshold value,
   *         it will produce rxfifo_full_int_raw interrupt.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  full_thrhd The full threshold value of the rxfifo. `full_thrhd` should be less than `UART_LL_FIFO_DEF_LEN`.
   *
   * @return None.
   */
  static inline void uart_ll_set_rxfifo_full_thr(uart_dev_t *hw, uint16_t full_thrhd)
  {
      hw->conf1.rxfifo_full_thrhd = full_thrhd;
  }
  
  /**
   * @brief  Set the txfifo empty threshold. when the data length in txfifo is less than threshold value,
   *         it will produce txfifo_empty_int_raw interrupt.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  empty_thrhd The empty threshold of txfifo.
   *
   * @return None.
   */
  static inline void uart_ll_set_txfifo_empty_thr(uart_dev_t *hw, uint16_t empty_thrhd)
  {
      hw->conf1.txfifo_empty_thrhd = empty_thrhd;
  }
  
  /**
   * @brief  Set the UART rx-idle threshold value. when receiver takes more time than rx_idle_thrhd to receive a byte data,
   *         it will produce frame end signal for uhci to stop receiving data.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  rx_idle_thr The rx-idle threshold to be set.
   *
   * @return None.
   */
  static inline void uart_ll_set_rx_idle_thr(uart_dev_t *hw, uint32_t rx_idle_thr)
  {
      hw->idle_conf.rx_idle_thrhd = rx_idle_thr;
  }
  
  /**
   * @brief  Configure the duration time between transfers.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  idle_num the duration time between transfers.
   *
   * @return None.
   */
  static inline void uart_ll_set_tx_idle_num(uart_dev_t *hw, uint32_t idle_num)
  {
      hw->idle_conf.tx_idle_num = idle_num;
  }
  
  /**
   * @brief  Configure the timeout value for receiver receiving a byte, and enable rx timeout function.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  tout_thr The timeout value. The rx timeout function will be disabled if `tout_thr == 0`.
   *
   * @return None.
   */
  static inline void uart_ll_set_rx_tout(uart_dev_t *hw, uint8_t tout_thr)
  {
      if(tout_thr > 0) {
          hw->mem_conf.rx_tout_thrhd = tout_thr;
          hw->conf1.rx_tout_en = 1;
      } else {
          hw->conf1.rx_tout_en = 0;
      }
  }
  
  /**
   * @brief  Configure the transmiter to send break chars.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  break_num The number of the break chars need to be send.
   *
   * @return None.
   */
  static inline void uart_ll_tx_break(uart_dev_t *hw, uint32_t break_num)
  {
      if(break_num > 0) {
          hw->idle_conf.tx_brk_num = break_num;
          hw->conf0.txd_brk = 1;
      } else {
          hw->conf0.txd_brk = 0;
      }
  }
  
  /**
   * @brief  Configure the UART hardware flow control.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  flow_ctrl The hw flow control configuration.
   * @param  rx_thrs The rx flow control signal will be active if the data length in rxfifo is more than this value.
   *
   * @return None.
   */
  static inline void uart_ll_set_hw_flow_ctrl(uart_dev_t *hw, uart_hw_flowcontrol_t flow_ctrl, uint32_t rx_thrs)
  {
      //only when UART_HW_FLOWCTRL_RTS is set , will the rx_thresh value be set.
      if(flow_ctrl & UART_HW_FLOWCTRL_RTS) {
          hw->mem_conf.rx_flow_thrhd = rx_thrs;
          hw->conf1.rx_flow_en = 1;
      } else {
          hw->conf1.rx_flow_en = 0;
      }
      if(flow_ctrl & UART_HW_FLOWCTRL_CTS) {
          hw->conf0.tx_flow_en = 1;
      } else {
          hw->conf0.tx_flow_en = 0;
      }
  }
  
  /**
   * @brief  Configure the hardware flow control.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  flow_ctrl A pointer to accept the hw flow control configuration.
   *
   * @return None.
   */
  static inline void uart_ll_get_hw_flow_ctrl(uart_dev_t *hw, uart_hw_flowcontrol_t *flow_ctrl)
  {
      *flow_ctrl = UART_HW_FLOWCTRL_DISABLE;
      if(hw->conf1.rx_flow_en) {
          *flow_ctrl |= UART_HW_FLOWCTRL_RTS;
      }
      if(hw->conf0.tx_flow_en) {
          *flow_ctrl |= UART_HW_FLOWCTRL_CTS;
      }
  }
  
  /**
   * @brief  Configure the software flow control.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  flow_ctrl The UART sofware flow control settings.
   * @param  sw_flow_ctrl_en Set true to enable software flow control, otherwise set it false.
   *
   * @return None.
   */
  static inline void uart_ll_set_sw_flow_ctrl(uart_dev_t *hw, uart_sw_flowctrl_t *flow_ctrl, bool sw_flow_ctrl_en)
  {
      if(sw_flow_ctrl_en) {
          hw->flow_conf.xonoff_del = 1;
          hw->flow_conf.sw_flow_con_en = 1;
          hw->swfc_conf1.xon_threshold = flow_ctrl->xon_thrd;
          hw->swfc_conf0.xoff_threshold = flow_ctrl->xoff_thrd;
          hw->swfc_conf1.xon_char = flow_ctrl->xon_char;
          hw->swfc_conf0.xoff_char = flow_ctrl->xoff_char;
      } else {
          hw->flow_conf.sw_flow_con_en = 0;
          hw->flow_conf.xonoff_del = 0;
      }
  }
  
  /**
   * @brief  Configure the AT cmd char. When the receiver receives a continuous AT cmd char, it will produce at_cmd_char_det interrupt.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  cmd_char The AT cmd char configuration.The configuration member is:
   *         - cmd_char The AT cmd character
   *         - char_num The number of received AT cmd char must be equal to or greater than this value
   *         - gap_tout The interval between each AT cmd char, when the duration is less than this value, it will not take this data as AT cmd char
   *         - pre_idle The idle time before the first AT cmd char, when the duration is less than this value, it will not take the previous data as the last AT cmd char
   *         - post_idle The idle time after the last AT cmd char, when the duration is less than this value, it will not take this data as the first AT cmd char
   *
   * @return None.
   */
  static inline void uart_ll_set_at_cmd_char(uart_dev_t *hw, uart_at_cmd_t *cmd_char)
  {
      hw->at_cmd_char.data = cmd_char->cmd_char;
      hw->at_cmd_char.char_num = cmd_char->char_num;
      hw->at_cmd_postcnt.post_idle_num = cmd_char->post_idle;
      hw->at_cmd_precnt.pre_idle_num = cmd_char->pre_idle;
      hw->at_cmd_gaptout.rx_gap_tout = cmd_char->gap_tout;
  }
  
  /**
   * @brief  Set the UART data bit mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  data_bit The data bit mode to be set.
   *
   * @return None.
   */
  static inline void uart_ll_set_data_bit_num(uart_dev_t *hw, uart_word_length_t data_bit)
  {
      hw->conf0.bit_num = data_bit;
  }
  
  /**
   * @brief  Get the UART source clock.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  source_clk The pointer to accept the UART source clock configuration.
   *
   * @return None.
   */
  static inline void uart_ll_get_sclk(uart_dev_t *hw, uart_sclk_t* source_clk)
  {
      *source_clk = hw->conf0.tick_ref_always_on ? UART_SCLK_APB : UART_SCLK_REF_TICK;
  }
  
  /**
   * @brief  Set the rts active level.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  level The rts active level, 0 or 1.
   *
   * @return None.
   */
  static inline void uart_ll_set_rts_active_level(uart_dev_t *hw, int level)
  {
      hw->conf0.sw_rts = level & 0x1;
  }
  
  /**
   * @brief  Set the dtr active level.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  level The dtr active level, 0 or 1.
   *
   * @return None.
   */
  static inline void uart_ll_set_dtr_active_level(uart_dev_t *hw, int level)
  {
      hw->conf0.sw_dtr = level & 0x1;
  }
  
  /**
   * @brief  Set the UART wakeup threshold.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  wakeup_thrd The wakeup threshold value to be set. When the input rx edge changes more than this value,
   *         the UART will active from light sleeping mode.
   *
   * @return None.
   */
  static inline void uart_ll_set_wakeup_thrd(uart_dev_t *hw, uint32_t wakeup_thrd)
  {
      hw->sleep_conf.active_threshold = wakeup_thrd - SOC_UART_MIN_WAKEUP_THRESH;
  }
  
  /**
   * @brief  Configure the UART work in normal mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None.
   */
  static inline void uart_ll_set_mode_normal(uart_dev_t *hw)
  {
      hw->rs485_conf.en = 0;
      hw->rs485_conf.tx_rx_en = 0;
      hw->rs485_conf.rx_busy_tx_en = 0;
      hw->conf0.irda_en = 0;
  }
  
  /**
   * @brief  Configure the UART work in rs485_app_ctrl mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None.
   */
  static inline void uart_ll_set_mode_rs485_app_ctrl(uart_dev_t *hw)
  {
      // Application software control, remove echo
      hw->rs485_conf.rx_busy_tx_en = 1;
      hw->conf0.irda_en = 0;
      hw->conf0.sw_rts = 0;
      hw->conf0.irda_en = 0;
      hw->rs485_conf.en = 1;
  }
  
  /**
   * @brief  Configure the UART work in rs485_half_duplex mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None.
   */
  static inline void uart_ll_set_mode_rs485_half_duplex(uart_dev_t *hw)
  {
      // Enable receiver, sw_rts = 1  generates low level on RTS pin
      hw->conf0.sw_rts = 1;
      // Must be set to 0 to automatically remove echo
      hw->rs485_conf.tx_rx_en = 0;
      // This is to void collision
      hw->rs485_conf.rx_busy_tx_en = 1;
      hw->conf0.irda_en = 0;
      hw->rs485_conf.en = 1;
  }
  
  /**
   * @brief  Configure the UART work in collision_detect mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None.
   */
  static inline void uart_ll_set_mode_collision_detect(uart_dev_t *hw)
  {
      hw->conf0.irda_en = 0;
      // Transmitters output signal loop back to the receivers input signal
      hw->rs485_conf.tx_rx_en = 1 ;
      // Transmitter should send data when the receiver is busy
      hw->rs485_conf.rx_busy_tx_en = 1;
      hw->conf0.sw_rts = 0;
      hw->rs485_conf.en = 1;
  }
  
  /**
   * @brief  Configure the UART work in irda mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return None.
   */
  static inline void uart_ll_set_mode_irda(uart_dev_t *hw)
  {
      hw->rs485_conf.en = 0;
      hw->rs485_conf.tx_rx_en = 0;
      hw->rs485_conf.rx_busy_tx_en = 0;
      hw->conf0.sw_rts = 0;
      hw->conf0.irda_en = 1;
  }
  
  /**
   * @brief  Set uart mode.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  mode The UART mode to be set.
   *
   * @return None.
   */
  static inline void uart_ll_set_mode(uart_dev_t *hw, uart_mode_t mode)
  {
      switch (mode) {
          default:
          case UART_MODE_UART:
              uart_ll_set_mode_normal(hw);
              break;
          case UART_MODE_RS485_COLLISION_DETECT:
              uart_ll_set_mode_collision_detect(hw);
              break;
          case UART_MODE_RS485_APP_CTRL:
              uart_ll_set_mode_rs485_app_ctrl(hw);
              break;
          case UART_MODE_RS485_HALF_DUPLEX:
              uart_ll_set_mode_rs485_half_duplex(hw);
              break;
          case UART_MODE_IRDA:
              uart_ll_set_mode_irda(hw);
              break;
      }
  }
  
  /**
   * @brief  Get the UART AT cmd char configuration.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  cmd_char The Pointer to accept value of UART AT cmd char.
   * @param  char_num Pointer to accept the repeat number of UART AT cmd char.
   *
   * @return None.
   */
  static inline void uart_ll_get_at_cmd_char(uart_dev_t *hw, uint8_t *cmd_char, uint8_t *char_num)
  {
      *cmd_char = hw->at_cmd_char.data;
      *char_num = hw->at_cmd_char.char_num;
  }
  
  /**
   * @brief  Get the UART wakeup threshold value.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return The UART wakeup threshold value.
   */
  static inline uint32_t uart_ll_get_wakeup_thrd(uart_dev_t *hw)
  {
      return hw->sleep_conf.active_threshold + SOC_UART_MIN_WAKEUP_THRESH;
  }
  
  /**
   * @brief  Get the UART data bit configuration.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  data_bit The pointer to accept the UART data bit configuration.
   *
   * @return The bit mode.
   */
  static inline void uart_ll_get_data_bit_num(uart_dev_t *hw, uart_word_length_t *data_bit)
  {
      *data_bit = hw->conf0.bit_num;
  }
  
  /**
   * @brief  Check if the UART sending state machine is in the IDLE state.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return True if the state machine is in the IDLE state, otherwise false is returned.
   */
  static inline bool uart_ll_is_tx_idle(uart_dev_t *hw)
  {
      return ((hw->status.txfifo_cnt == 0) && (hw->fsm_status.st_utx_out == 0));
  }
  
  /**
   * @brief  Check if the UART rts flow control is enabled.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return True if hw rts flow control is enabled, otherwise false is returned.
   */
  static inline bool uart_ll_is_hw_rts_en(uart_dev_t *hw)
  {
      return hw->conf1.rx_flow_en;
  }
  
  /**
   * @brief  Check if the UART cts flow control is enabled.
   *
   * @param  hw Beginning address of the peripheral registers.
   *
   * @return True if hw cts flow control is enabled, otherwise false is returned.
   */
  static inline bool uart_ll_is_hw_cts_en(uart_dev_t *hw)
  {
      return hw->conf0.tx_flow_en;
  }
  
  /**
   * @brief Configure TX signal loop back to RX module, just for the testing purposes
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  loop_back_en Set ture to enable the loop back function, else set it false.
   *
   * @return None
   */
  static inline void uart_ll_set_loop_back(uart_dev_t *hw, bool loop_back_en)
  {
      hw->conf0.loopback = loop_back_en;
  }
  
  /**
   * @brief  Inverse the UART signal with the given mask.
   *
   * @param  hw Beginning address of the peripheral registers.
   * @param  inv_mask The UART signal bitmap needs to be inversed.
   *         Use the ORred mask of `uart_signal_inv_t`;
   *
   * @return None.
   */
  static inline void uart_ll_inverse_signal(uart_dev_t *hw, uint32_t inv_mask)
  {
      typeof(hw->conf0) conf0_reg = hw->conf0;
      conf0_reg.irda_tx_inv |= (inv_mask & UART_SIGNAL_IRDA_TX_INV) ? 1 : 0;
      conf0_reg.irda_rx_inv |= (inv_mask & UART_SIGNAL_IRDA_RX_INV) ? 1 : 0;
      conf0_reg.rxd_inv |= (inv_mask & UART_SIGNAL_RXD_INV) ? 1 : 0;
      conf0_reg.cts_inv |= (inv_mask & UART_SIGNAL_CTS_INV) ? 1 : 0;
      conf0_reg.dsr_inv |= (inv_mask & UART_SIGNAL_DSR_INV) ? 1 : 0;
      conf0_reg.txd_inv |= (inv_mask & UART_SIGNAL_TXD_INV) ? 1 : 0;
      conf0_reg.rts_inv |= (inv_mask & UART_SIGNAL_RTS_INV) ? 1 : 0;
      conf0_reg.dtr_inv |= (inv_mask & UART_SIGNAL_DTR_INV) ? 1 : 0;
      hw->conf0.val = conf0_reg.val;
  }
  