/*
   * Copyright (C) 2015 Freie Universität Berlin
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @ingroup     cpu_msp430fxyz
   * @ingroup     drivers_periph_uart
   * @{
   *
   * @file
   * @brief       Low-level UART driver implementation
   *
   * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
   *
   * @}
   */
  
  #include "cpu.h"
  #include "periph_cpu.h"
  #include "periph_conf.h"
  #include "periph/uart.h"
  
  /**
   * @brief   Keep track of the interrupt context
   * @{
   */
  static uart_rx_cb_t ctx_rx_cb;
  static void *ctx_isr_arg;
  /** @} */
  
  static int init_base(uart_t uart, uint32_t baudrate);
  
  /* per default, we use the legacy MSP430 USART module for UART functionality */
  #ifndef UART_USE_USCI
  
  int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
  {
      int res = init_base(uart, baudrate);
      if (res != UART_OK) {
          return res;
      }
  
      /* save interrupt context */
      ctx_rx_cb = rx_cb;
      ctx_isr_arg = arg;
      /* reset interrupt flags and enable RX interrupt */
      UART_IE &= ~(UART_IE_TX_BIT);
      UART_IF &= ~(UART_IE_RX_BIT);
      UART_IF |=  (UART_IE_TX_BIT);
      UART_IE |=  (UART_IE_RX_BIT);
      return UART_OK;
  }
  
  static int init_base(uart_t uart, uint32_t baudrate)
  {
      if (uart != 0) {
          return UART_NODEV;
      }
  
      /* get the default UART for now -> TODO: enable for multiple devices */
      msp_usart_t *dev = UART_BASE;
  
      /* power off and reset device */
      uart_poweroff(uart);
      dev->CTL = USART_CTL_SWRST;
      /* configure to 8N1 and using the SMCLK*/
      dev->CTL |= USART_CTL_CHAR;
      dev->TCTL = (USART_TCTL_TXEPT | USART_TCTL_SSEL_SMCLK);
      dev->RCTL = 0x00;
      /* baudrate configuration */
      uint16_t br = (uint16_t)(CLOCK_CMCLK / baudrate);
      dev->BR0 = (uint8_t)br;
      dev->BR1 = (uint8_t)(br >> 8);
      /* TODO: calculate value for modulation register */
      dev->MCTL = 0;
      /* configure pins -> TODO: move into GPIO driver (once implemented) */
      UART_PORT->SEL |= (UART_RX_PIN | UART_TX_PIN);
      UART_PORT->OD |= UART_RX_PIN;
      UART_PORT->OD &= ~(UART_TX_PIN);
      UART_PORT->DIR |= UART_TX_PIN;
      UART_PORT->DIR &= ~(UART_RX_PIN);
      /* enable receiver and transmitter */
      uart_poweron(uart);
      /* and finally release the software reset bit */
      dev->CTL &= ~(USART_CTL_SWRST);
      return UART_OK;
  }
  
  void uart_write(uart_t uart, const uint8_t *data, size_t len)
  {
      (void)uart;
      msp_usart_t *dev = UART_BASE;
  
      for (size_t i = 0; i < len; i++) {
          while (!(dev->TCTL & USART_TCTL_TXEPT)) {}
          dev->TXBUF = data[i];
      }
  }
  
  void uart_poweron(uart_t uart)
  {
      UART_ME |= UART_ME_BITS;
  }
  
  void uart_poweroff(uart_t uart)
  {
      UART_ME &= ~(UART_ME_BITS);
  }
  
  ISR(UART_RX_ISR, isr_uart_0_rx)
  {
      __enter_isr();
  
      /* read character (resets interrupt flag) */
      char c = UART_BASE->RXBUF;
  
      /* only call callback if there was no receive error */
      if(! (UART_BASE->RCTL & RXERR)) {
          ctx_rx_cb(ctx_isr_arg, c);
      }
  
      __exit_isr();
  }
  
  /* we use alternative UART code in case the board used the USCI module for UART
   * in case of the (older) USART module */
  #else
  
  int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
  {
      if (init_base(uart, baudrate) < 0) {
          return -1;
      }
  
      /* save interrupt context */
      ctx_rx_cb = rx_cb;
      ctx_isr_arg = arg;
      /* reset interrupt flags and enable RX interrupt */
      UART_IF &= ~(UART_IE_RX_BIT);
      UART_IF |=  (UART_IE_TX_BIT);
      UART_IE |=  (UART_IE_RX_BIT);
      UART_IE &= ~(UART_IE_TX_BIT);
      return 0;
  }
  
  static int init_base(uart_t uart, uint32_t baudrate)
  {
      if (uart != 0) {
          return -1;
      }
  
      /* get the default UART for now -> TODO: enable for multiple devices */
      msp_usci_t *dev = UART_BASE;
  
      /* put device in reset mode while configuration is going on */
      dev->ACTL1 = USCI_ACTL1_SWRST;
      /* configure to UART, using SMCLK in 8N1 mode */
      dev->ACTL1 |= USCI_ACTL1_SSEL_SMCLK;
      dev->ACTL0 = 0;
      dev->ASTAT = 0;
      /* configure baudrate */
      uint32_t base = ((CLOCK_CMCLK << 7)  / baudrate);
      uint16_t br = (uint16_t)(base >> 7);
      uint8_t brs = (((base & 0x3f) * 8) >> 7);
      dev->ABR0 = (uint8_t)br;
      dev->ABR1 = (uint8_t)(br >> 8);
      dev->AMCTL = (brs << USCI_AMCTL_BRS_SHIFT);
      /* pin configuration -> TODO: move to GPIO driver once implemented */
      UART_RX_PORT->SEL |= UART_RX_PIN;
      UART_TX_PORT->SEL |= UART_TX_PIN;
      UART_RX_PORT->DIR &= ~(UART_RX_PIN);
      UART_TX_PORT->DIR |= UART_TX_PIN;
      /* releasing the software reset bit starts the UART */
      dev->ACTL1 &= ~(USCI_ACTL1_SWRST);
      return 0;
  }
  
  void uart_write(uart_t uart, const uint8_t *data, size_t len)
  {
      (void)uart;
  
      for (size_t i = 0; i < len; i++) {
          while (!(UART_IF & UART_IE_TX_BIT)) {}
          UART_BASE->ATXBUF = data[i];
      }
  }
  
  void uart_poweron(uart_t uart)
  {
      (void)uart;
      /* n/a */
  }
  
  void uart_poweroff(uart_t uart)
  {
      (void)uart;
      /* n/a */
  }
  
  ISR(UART_RX_ISR, isr_uart_0_rx)
  {
      __enter_isr();
  
      uint8_t stat = UART_BASE->ASTAT;
      uint8_t data = (uint8_t)UART_BASE->ARXBUF;
  
      if (stat & (USCI_ASTAT_FE | USCI_ASTAT_OE | USCI_ASTAT_PE | USCI_ASTAT_BRK)) {
          /* some error which we do not handle, just do a pseudo read to reset the
           * status register */
          (void)data;
      }
      else {
          ctx_rx_cb(ctx_isr_arg, data);
      }
  
      __exit_isr();
  }
  
  #endif