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// # << NEORV32: neorv32_uart.c - Universal Asynchronous Receiver/Transmitter (UART) HW Driver >>  #

// # ********************************************************************************************* #

// # BSD 3-Clause License                                                                          #

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// # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #

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// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

// #################################################################################################

/**********************************************************************//**

 * @file neorv32_uart.c

 * @author Stephan Nolting

 * @brief Universal asynchronous receiver/transmitter (UART) HW driver source file.

 *

 * @note These functions should only be used if the UART unit was synthesized (IO_UART_USE = true).

 **************************************************************************/

#include "neorv32.h"

#include "neorv32_uart.h"

#include <string.h>

/// \cond

// Private functions

static void __neorv32_uart_itoa(uint32_t x, char *res) __attribute__((unused)); // GCC: do not ouput a warning when this variable is unused

static void __neorv32_uart_tohex(uint32_t x, char *res) __attribute__((unused)); // GCC: do not ouput a warning when this variable is unused

/// \endcond

/**********************************************************************//**

 * Check if UART unit was synthesized.

 *

 * @return 0 if UART was not synthesized, 1 if UART is available.

 **************************************************************************/

int neorv32_uart_available(void) {

  if (neorv32_cpu_csr_read(CSR_MFEATURES) & (1 << CPU_MFEATURES_IO_UART)) {

    return 1;

  }

  else {

    return 0;

  }

}

/**********************************************************************//**

 * Enable and configure UART.

 *

 * @param[in] baudrate Targeted BAUD rate (e.g. 9600).

 * @param[in] rx_irq Enable RX interrupt (data received) when 1.

 * @param[in] tx_irq Enable TX interrupt (transmission done) when 1.

 **************************************************************************/

void neorv32_uart_setup(uint32_t baudrate, uint8_t rx_irq, uint8_t tx_irq) {

  UART_CT = 0; // reset

  // raw baud rate prescaler

  uint32_t clock = neorv32_cpu_csr_read(CSR_MCLOCK);

  uint16_t i = 0; // BAUD rate divisor

  uint8_t p = 0; // prsc = CLK/2

  while (clock >= 2*baudrate) {

    clock -= 2*baudrate;

    i++;

  }

  // find clock prsc

  while (i >= 0x0fff) {

    if ((p == 2) || (p == 4))

      i >>= 3;

    else

      i >>= 1;

    p++;

  }

  uint32_t prsc = (uint32_t)p;

  prsc = prsc << UART_CT_PRSC0;

  uint32_t baud = (uint32_t)i;

  baud = baud << UART_CT_BAUD00;

  uint32_t uart_en = 1;

  uart_en = uart_en << UART_CT_EN;

  uint32_t rx_irq_en = (uint32_t)(rx_irq & 1);

  rx_irq_en = rx_irq_en << UART_CT_RX_IRQ;

  uint32_t tx_irq_en = (uint32_t)(tx_irq & 1);

  tx_irq_en = tx_irq_en << UART_CT_TX_IRQ;

  UART_CT = prsc | baud | uart_en | rx_irq_en | tx_irq_en;

}

/**********************************************************************//**

 * Disable UART.

 **************************************************************************/

void neorv32_uart_disable(void) {

  UART_CT &= ~((uint32_t)(1 << UART_CT_EN));

}

/**********************************************************************//**

 * Send single char via UART.

 *

 * @note This function is blocking.

 *

 * @param[in] c Char to be send.

 **************************************************************************/

void neorv32_uart_putc(char c) {

  // wait for previous transfer to finish

  while ((UART_CT & (1<<UART_CT_TX_BUSY)) != 0);

  UART_DATA = ((uint32_t)c) << UART_DATA_LSB;

}

/**********************************************************************//**

 * Get char from UART.

 *

 * @note This function is blocking.

 *

 * @return Received char.

 **************************************************************************/

char neorv32_uart_getc(void) {

  uint32_t d = 0;

  while (1) {

    d = UART_DATA;

    if ((d & (1<<UART_DATA_AVAIL)) != 0) { // char received?

      return (char)d;

    }

  }

}

/**********************************************************************//**

 * Check if UARt has received a char.

 *

 * @note This function is non-blocking.

 * @note Use neorv32_uart_char_received_get(void) to get the char.

 *

 * @return =!0 when a char has been received.

 **************************************************************************/

int neorv32_uart_char_received(void) {

  if ((UART_DATA & (1<<UART_DATA_AVAIL)) != 0) {

    return 1;

  }

  else {

    return 0;

  }

}

/**********************************************************************//**

 * Get a received char.

 *

 * @note This function is non-blocking.

 * @note Should only be used in combination with neorv32_uart_char_received(void).

 *

 * @return Received char.

 **************************************************************************/

char neorv32_uart_char_received_get(void) {

  return (char)UART_DATA;

}

/**********************************************************************//**

 * Print string (zero-terminated) via UART. Print full line break "\r\n" for every '\n'.

 *

 * @note This function is blocking.

 *

 * @param[in] s Pointer to string.

 **************************************************************************/

void neorv32_uart_print(char *s) {

  char c = 0;

  while ((c = *s++)) {

    if (c == '\n') {

      neorv32_uart_putc('\r');

    }

    neorv32_uart_putc(c);

  }

}

/**********************************************************************//**

 * Private function for 'neorv32_printf' to convert into decimal.

 *

 * @param[in] x Unsigned input number.

 * @param[in,out] res Pointer for storing the reuslting number string (11 chars).

 **************************************************************************/

static void __neorv32_uart_itoa(uint32_t x, char *res) {

  static const char numbers[10] = "0123456789";

  char buffer1[11];

  uint16_t i, j;

  buffer1[10] = '\0';

  res[10] = '\0';

  // convert

  for (i=0; i<10; i++) {

    buffer1[i] = numbers[x%10];

    x /= 10;

  }

  // delete 'leading' zeros

  for (i=9; i!=0; i--) {

    if (buffer1[i] == '0')

      buffer1[i] = '\0';

    else

      break;

  }

  // reverse

  j = 0;

  do {

    if (buffer1[i] != '\0')

      res[j++] = buffer1[i];

  } while (i--);

  res[j] = '\0'; // terminate result string

}

/**********************************************************************//**

 * Private function for 'neorv32_printf' to convert into hexadecimal.

 *

 * @param[in] x Unsigned input number.

 * @param[in,out] res Pointer for storing the reuslting number string (9 chars).

 **************************************************************************/

static void __neorv32_uart_tohex(uint32_t x, char *res) {

  static const char symbols[16] = "0123456789abcdef";

  int i;

  for (i=0; i<8; i++) { // nibble by bibble

    uint32_t num_tmp = x >> (4*i);

    res[7-i] = (char)symbols[num_tmp & 0x0f];

  }

  res[8] = '\0'; // terminate result string

}

/**********************************************************************//**

 * Custom version of 'printf' function.

 *

 * @note This function is blocking.

 *

 * @param[in] format Pointer to format string.

 *

 * <TABLE>

 * <TR><TD>%s</TD><TD>String (array of chars, zero-terminated)</TD></TR>

 * <TR><TD>%c</TD><TD>Single char</TD></TR>

 * <TR><TD>%i</TD><TD>32-bit signed number, printed as decimal</TD></TR>

 * <TR><TD>%u</TD><TD>32-bit unsigned number, printed as decimal</TD></TR>

 * <TR><TD>%x</TD><TD>32-bit number, printed as 8-char hexadecimal</TD></TR>

 * </TABLE>

 **************************************************************************/

void neorv32_uart_printf(char *format, ...) {

  char c, string_buf[11];

  int32_t n;

  va_list a;

  va_start(a, format);

  while ((c = *format++)) {

    if (c == '%') {

      c = *format++;

      switch (c) {

        case 's': // string

          neorv32_uart_print(va_arg(a, char*));

          break;

        case 'c': // char

          neorv32_uart_putc((char)va_arg(a, int));

          break;

        case 'i': // 32-bit signed

          n = (int32_t)va_arg(a, int32_t);

          if (n < 0) {

            n = -n;

            neorv32_uart_putc('-');

          }

          __neorv32_uart_itoa((uint32_t)n, string_buf);

          neorv32_uart_print(string_buf);

          break;

        case 'u': // 32-bit unsigned

          __neorv32_uart_itoa(va_arg(a, uint32_t), string_buf);

          neorv32_uart_print(string_buf);

          break;

        case 'x': // 32-bit hexadecimal

          __neorv32_uart_tohex(va_arg(a, uint32_t), string_buf);

          neorv32_uart_print(string_buf);

          break;

        default:

          return;

      }

    }

    else {

      if (c == '\n') {

        neorv32_uart_putc('\r');

      }

      neorv32_uart_putc(c);

    }

  }

  va_end(a);

}

/**********************************************************************//**

 * Simplified custom version of 'scanf' function.

 *

 * @note This function is blocking.

 *

 * @param[in,out] buffer Pointer to array of chars to store string.

 * @param[in] max_size Maximum number of chars to sample.

 * @param[in] echo Echo UART input when 1.

 * @return Number of chars read.

 **************************************************************************/

int neorv32_uart_scan(char *buffer, int max_size, int echo) {

  char c = 0;

  int length = 0;

  while (1) {

    c = neorv32_uart_getc();

    if (c == '\b') { // BACKSPACE

      if (length != 0) {

        if (echo) {

          neorv32_uart_print("\b \b"); // delete last char in console

        }

        buffer--;

        length--;

      }

    }

    else if (c == '\r') // carriage return

      break;

    else if ((c >= ' ') && (c <= '~') && (length < (max_size-1))) {

      if (echo) {

        neorv32_uart_putc(c); // echo

      }

      *buffer++ = c;

      length++;

    }

  }

  *buffer = '\0'; // terminate string

  return length;

}