MinimumSerial.cpp

/**
 * Copyright (c) 2011-2018 Bill Greiman
 * This file is part of the SdFat library for SD memory cards.
 *
 * MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */
#include "SysCall.h"
#if defined(UDR0) || defined(DOXYGEN)
#include "MinimumSerial.h"
const uint16_t MIN_2X_BAUD = F_CPU/(4*(2*0XFFF + 1)) + 1;
//------------------------------------------------------------------------------
int MinimumSerial::available() {
  return UCSR0A & (1 << RXC0) ? 1 : 0;
}
//------------------------------------------------------------------------------
void MinimumSerial::begin(uint32_t baud) {
  uint16_t baud_setting;
  // don't worry, the compiler will squeeze out F_CPU != 16000000UL
  if ((F_CPU != 16000000UL || baud != 57600) && baud > MIN_2X_BAUD) {
    // Double the USART Transmission Speed
    UCSR0A = 1 << U2X0;
    baud_setting = (F_CPU / 4 / baud - 1) / 2;
  } else {
    // hardcoded exception for compatibility with the bootloader shipped
    // with the Duemilanove and previous boards and the firmware on the 8U2
    // on the Uno and Mega 2560.
    UCSR0A = 0;
    baud_setting = (F_CPU / 8 / baud - 1) / 2;
  }
  // assign the baud_setting
  UBRR0H = baud_setting >> 8;
  UBRR0L = baud_setting;
  // enable transmit and receive
  UCSR0B |= (1 << TXEN0) | (1 << RXEN0);
}
//------------------------------------------------------------------------------
void MinimumSerial::flush() {
  while (((1 << UDRIE0) & UCSR0B) || !(UCSR0A & (1 << UDRE0))) {}
}
//------------------------------------------------------------------------------
int MinimumSerial::read() {
  if (UCSR0A & (1 << RXC0)) {
    return UDR0;
  }
  return -1;
}
//------------------------------------------------------------------------------
size_t MinimumSerial::write(uint8_t b) {
  while (((1 << UDRIE0) & UCSR0B) || !(UCSR0A & (1 << UDRE0))) {}
  UDR0 = b;
  return 1;
}
#endif  //  defined(UDR0) || defined(DOXYGEN)