text: /* mbed Microcontroller Library
   * Copyright (c) 2006-2013 ARM Limited
   *
   * 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.
   */
  // math.h required for floating point operations for baud rate calculation
  #include <math.h>
  #include <string.h>
  
  #include "serial_api.h"
  #include "cmsis.h"
  #include "pinmap.h"
  #include "error.h"
  
  /******************************************************************************
   * INITIALIZATION
   ******************************************************************************/
  #define UART_NUM    1
  
  static const PinMap PinMap_UART_TX[] = {
      {P2_8 , UART_0, 0x02},
      {P3_5 , UART_0, 0x02},
      {P3_0 , UART_0, 0x03},
      {P1_7 , UART_0, 0x01},
      {NC   , NC    , 0x00}
  };
  
  static const PinMap PinMap_UART_RX[] = {
      {P2_7 , UART_0, 0x02},
      {P3_4 , UART_0, 0x02},
      {P3_1 , UART_0, 0x03},
      {P1_6 , UART_0, 0x01},
      {NC   , NC    , 0x00}
  };
  
  static uint32_t serial_irq_ids[UART_NUM] = {0};
  static uart_irq_handler irq_handler;
  
  int stdio_uart_inited = 0;
  serial_t stdio_uart;
  
  void serial_init(serial_t *obj, PinName tx, PinName rx) {
      int is_stdio_uart = 0;
      
      // determine the UART to use
      UARTName uart_tx = (UARTName)pinmap_peripheral(tx, PinMap_UART_TX);
      UARTName uart_rx = (UARTName)pinmap_peripheral(rx, PinMap_UART_RX);
      UARTName uart = (UARTName)pinmap_merge(uart_tx, uart_rx);
      if ((int)uart == NC) {
          error("Serial pinout mapping failed");
      }
      
      obj->uart = (LPC_UART_TypeDef *)uart;
      LPC_SYSCON->SYSAHBCLKCTRL |= (1<<12);
      
      // enable fifos and default rx trigger level
      obj->uart->FCR = 1 << 0  // FIFO Enable - 0 = Disables, 1 = Enabled
                     | 0 << 1  // Rx Fifo Reset
                     | 0 << 2  // Tx Fifo Reset
                     | 0 << 6; // Rx irq trigger level - 0 = 1 char, 1 = 4 chars, 2 = 8 chars, 3 = 14 chars
      
      // disable irqs
      obj->uart->IER = 0 << 0  // Rx Data available irq enable
                     | 0 << 1  // Tx Fifo empty irq enable
                     | 0 << 2; // Rx Line Status irq enable
      
      // set default baud rate and format
      serial_baud  (obj, 9600);
      serial_format(obj, 8, ParityNone, 1);
      
      // pinout the chosen uart
      pinmap_pinout(tx, PinMap_UART_TX);
      pinmap_pinout(rx, PinMap_UART_RX);
      
      // set rx/tx pins in PullUp mode
      pin_mode(tx, PullUp);
      pin_mode(rx, PullUp);
      
      switch (uart) {
          case UART_0: obj->index = 0; break;
      }
      
      is_stdio_uart = (uart == STDIO_UART) ? (1) : (0);
      
      if (is_stdio_uart) {
          stdio_uart_inited = 1;
          memcpy(&stdio_uart, obj, sizeof(serial_t));
      }
  }
  
  void serial_free(serial_t *obj) {
      serial_irq_ids[obj->index] = 0;
  }
  
  // serial_baud
  // set the baud rate, taking in to account the current SystemFrequency
  void serial_baud(serial_t *obj, int baudrate) {
      LPC_SYSCON->UARTCLKDIV = 0x1;
      uint32_t PCLK = SystemCoreClock;
      // First we check to see if the basic divide with no DivAddVal/MulVal
      // ratio gives us an integer result. If it does, we set DivAddVal = 0,
      // MulVal = 1. Otherwise, we search the valid ratio value range to find
      // the closest match. This could be more elegant, using search methods
      // and/or lookup tables, but the brute force method is not that much
      // slower, and is more maintainable.
      uint16_t DL = PCLK / (16 * baudrate);
      
      uint8_t DivAddVal = 0;
      uint8_t MulVal = 1;
      int hit = 0;
      uint16_t dlv;
      uint8_t mv, dav;
      if ((PCLK % (16 * baudrate)) != 0) {     // Checking for zero remainder
          int err_best = baudrate, b;
          for (mv = 1; mv < 16 && !hit; mv++)
          {
              for (dav = 0; dav < mv; dav++)
              {
                  // baudrate = PCLK / (16 * dlv * (1 + (DivAdd / Mul))
                  // solving for dlv, we get dlv = mul * PCLK / (16 * baudrate * (divadd + mul))
                  // mul has 4 bits, PCLK has 27 so we have 1 bit headroom which can be used for rounding
                  // for many values of mul and PCLK we have 2 or more bits of headroom which can be used to improve precision
                  // note: X / 32 doesn't round correctly. Instead, we use ((X / 16) + 1) / 2 for correct rounding
  
                  if ((mv * PCLK * 2) & 0x80000000) // 1 bit headroom
                      dlv = ((((2 * mv * PCLK) / (baudrate * (dav + mv))) / 16) + 1) / 2;
                  else // 2 bits headroom, use more precision
                      dlv = ((((4 * mv * PCLK) / (baudrate * (dav + mv))) / 32) + 1) / 2;
  
                  // datasheet says if DLL==DLM==0, then 1 is used instead since divide by zero is ungood
                  if (dlv == 0)
                      dlv = 1;
  
                  // datasheet says if dav > 0 then DL must be >= 2
                  if ((dav > 0) && (dlv < 2))
                      dlv = 2;
  
                  // integer rearrangement of the baudrate equation (with rounding)
                  b = ((PCLK * mv / (dlv * (dav + mv) * 8)) + 1) / 2;
  
                  // check to see how we went
                  b = abs(b - baudrate);
                  if (b < err_best)
                  {
                      err_best  = b;
  
                      DL        = dlv;
                      MulVal    = mv;
                      DivAddVal = dav;
  
                      if (b == baudrate)
                      {
                          hit = 1;
                          break;
                      }
                  }
              }
          }
      }
      
      // set LCR[DLAB] to enable writing to divider registers
      obj->uart->LCR |= (1 << 7);
      
      // set divider values
      obj->uart->DLM = (DL >> 8) & 0xFF;
      obj->uart->DLL = (DL >> 0) & 0xFF;
      obj->uart->FDR = (uint32_t) DivAddVal << 0
                     | (uint32_t) MulVal    << 4;
      
      // clear LCR[DLAB]
      obj->uart->LCR &= ~(1 << 7);
  }
  
  void serial_format(serial_t *obj, int data_bits, SerialParity parity, int stop_bits) {
      // 0: 1 stop bits, 1: 2 stop bits
      if (stop_bits != 1 && stop_bits != 2) {
          error("Invalid stop bits specified");
      }
      stop_bits -= 1;
      
      // 0: 5 data bits ... 3: 8 data bits
      if (data_bits < 5 || data_bits > 8) {
          error("Invalid number of bits (%d) in serial format, should be 5..8", data_bits);
      }
      data_bits -= 5;
  
      int parity_enable, parity_select;
      switch (parity) {
          case ParityNone: parity_enable = 0; parity_select = 0; break;
          case ParityOdd : parity_enable = 1; parity_select = 0; break;
          case ParityEven: parity_enable = 1; parity_select = 1; break;
          case ParityForced1: parity_enable = 1; parity_select = 2; break;
          case ParityForced0: parity_enable = 1; parity_select = 3; break;
          default:
              error("Invalid serial parity setting");
              return;
      }
      
      obj->uart->LCR = data_bits            << 0
                     | stop_bits            << 2
                     | parity_enable        << 3
                     | parity_select        << 4;
  }
  
  /******************************************************************************
   * INTERRUPTS HANDLING
   ******************************************************************************/
  static inline void uart_irq(uint32_t iir, uint32_t index) {
      // [Chapter 14] LPC17xx UART0/2/3: UARTn Interrupt Handling
      SerialIrq irq_type;
      switch (iir) {
          case 1: irq_type = TxIrq; break;
          case 2: irq_type = RxIrq; break;
          default: return;
      }
      
      if (serial_irq_ids[index] != 0)
          irq_handler(serial_irq_ids[index], irq_type);
  }
  
  void uart0_irq() {uart_irq((LPC_UART->IIR >> 1) & 0x7, 0);}
  
  void serial_irq_handler(serial_t *obj, uart_irq_handler handler, uint32_t id) {
      irq_handler = handler;
      serial_irq_ids[obj->index] = id;
  }
  
  void serial_irq_set(serial_t *obj, SerialIrq irq, uint32_t enable) {
      IRQn_Type irq_n = (IRQn_Type)0;
      uint32_t vector = 0;
      switch ((int)obj->uart) {
          case UART_0:
              irq_n=UART_IRQn;
              vector = (uint32_t)&uart0_irq;
              break;
          default:
              return;
      }
      
      if (enable) {
          obj->uart->IER |= 1 << irq;
          NVIC_SetVector(irq_n, vector);
          NVIC_EnableIRQ(irq_n);
      } else { // disable
          int all_disabled = 0;
          SerialIrq other_irq = (irq == RxIrq) ? (TxIrq) : (RxIrq);
  
          obj->uart->IER &= ~(1 << irq);
          all_disabled = (obj->uart->IER & (1 << other_irq)) == 0;
          
          if (all_disabled)
              NVIC_DisableIRQ(irq_n);
      }
  }
  
  /******************************************************************************
   * READ/WRITE
   ******************************************************************************/
  int serial_getc(serial_t *obj) {
      while (!serial_readable(obj));
      return obj->uart->RBR;
  }
  
  void serial_putc(serial_t *obj, int c) {
      while (!serial_writable(obj));
      obj->uart->THR = c;
  }
  
  int serial_readable(serial_t *obj) {
      return obj->uart->LSR & 0x01;
  }
  
  int serial_writable(serial_t *obj) {
      return obj->uart->LSR & 0x20;
  }
  
  void serial_clear(serial_t *obj) {
      obj->uart->FCR = 1 << 1  // rx FIFO reset
                     | 1 << 2  // tx FIFO reset
                     | 0 << 6; // interrupt depth
  }
  
  void serial_pinout_tx(PinName tx) {
      pinmap_pinout(tx, PinMap_UART_TX);
  }
  
  void serial_break_clear(serial_t *obj) {
      obj->uart->LCR &= ~(1 << 6);
  }
  
  void serial_break_set(serial_t *obj) {
      obj->uart->LCR |= 1 << 6;
  }
  