ardupilot/libraries/FastSerial/FastSerial.cpp

244 lines
6.7 KiB
C++
Raw Normal View History

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
//
// Interrupt-driven serial transmit/receive library.
//
// Copyright (c) 2010 Michael Smith. All rights reserved.
//
// Receive and baudrate calculations derived from the Arduino
// HardwareSerial driver:
//
// Copyright (c) 2006 Nicholas Zambetti. All right reserved.
//
// Transmit algorithm inspired by work:
//
// Code Jose Julio and Jordi Munoz. DIYDrones.com
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
//
//#include "../AP_Common/AP_Common.h"
#include "FastSerial.h"
#include "WProgram.h"
#if defined(UDR3)
# define FS_MAX_PORTS 4
#elif defined(UDR2)
# define FS_MAX_PORTS 3
#elif defined(UDR1)
# define FS_MAX_PORTS 2
#else
# define FS_MAX_PORTS 1
#endif
FastSerial::Buffer __FastSerial__rxBuffer[FS_MAX_PORTS];
FastSerial::Buffer __FastSerial__txBuffer[FS_MAX_PORTS];
// Constructor /////////////////////////////////////////////////////////////////
FastSerial::FastSerial(const uint8_t portNumber, volatile uint8_t *ubrrh, volatile uint8_t *ubrrl,
volatile uint8_t *ucsra, volatile uint8_t *ucsrb, const uint8_t u2x,
const uint8_t portEnableBits, const uint8_t portTxBits) :
_ubrrh(ubrrh),
_ubrrl(ubrrl),
_ucsra(ucsra),
_ucsrb(ucsrb),
_u2x(u2x),
_portEnableBits(portEnableBits),
_portTxBits(portTxBits),
_rxBuffer(&__FastSerial__rxBuffer[portNumber]),
_txBuffer(&__FastSerial__txBuffer[portNumber])
{
}
// Public Methods //////////////////////////////////////////////////////////////
void FastSerial::begin(long baud)
{
begin(baud, 0, 0);
}
void FastSerial::begin(long baud, unsigned int rxSpace, unsigned int txSpace)
{
uint16_t ubrr;
bool use_u2x = true;
// if we are currently open...
if (_open) {
// If the caller wants to preserve the buffer sizing, work out what
// it currently is...
if (0 == rxSpace)
rxSpace = _rxBuffer->mask + 1;
if (0 == txSpace)
txSpace = _txBuffer->mask + 1;
// close the port in its current configuration, clears _open
end();
}
// allocate buffers
if (!_allocBuffer(_rxBuffer, rxSpace ? : _default_rx_buffer_size) || !_allocBuffer(_txBuffer, txSpace ? : _default_tx_buffer_size)) {
end();
return; // couldn't allocate buffers - fatal
}
// reset buffer pointers
_txBuffer->head = _txBuffer->tail = 0;
_rxBuffer->head = _rxBuffer->tail = 0;
// mark the port as open
_open = true;
// If the user has supplied a new baud rate, compute the new UBRR value.
if (baud > 0) {
#if F_CPU == 16000000UL
// 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.
if (baud == 57600)
use_u2x = false;
#endif
if (use_u2x) {
ubrr = (F_CPU / 4 / baud - 1) / 2;
} else {
ubrr = (F_CPU / 8 / baud - 1) / 2;
}
*_ucsra = use_u2x ? _BV(_u2x) : 0;
*_ubrrh = ubrr >> 8;
*_ubrrl = ubrr;
}
*_ucsrb |= _portEnableBits;
}
void FastSerial::end()
{
*_ucsrb &= ~(_portEnableBits | _portTxBits);
_freeBuffer(_rxBuffer);
_freeBuffer(_txBuffer);
_open = false;
}
int FastSerial::available(void)
{
if (!_open)
return (-1);
return ((_rxBuffer->head - _rxBuffer->tail) & _rxBuffer->mask);
}
int FastSerial::read(void)
{
uint8_t c;
// if the head and tail are equal, the buffer is empty
if (!_open || (_rxBuffer->head == _rxBuffer->tail))
return (-1);
// pull character from tail
c = _rxBuffer->bytes[_rxBuffer->tail];
_rxBuffer->tail = (_rxBuffer->tail + 1) & _rxBuffer->mask;
return (c);
}
int FastSerial::peek(void)
{
// if the head and tail are equal, the buffer is empty
if (!_open || (_rxBuffer->head == _rxBuffer->tail))
return (-1);
// pull character from tail
return (_rxBuffer->bytes[_rxBuffer->tail]);
}
void FastSerial::flush(void)
{
// don't reverse this or there may be problems if the RX interrupt
// occurs after reading the value of _rxBuffer->head but before writing
// the value to _rxBuffer->tail; the previous value of head
// may be written to tail, making it appear as if the buffer
// don't reverse this or there may be problems if the RX interrupt
// occurs after reading the value of head but before writing
// the value to tail; the previous value of rx_buffer_head
// may be written to tail, making it appear as if the buffer
// were full, not empty.
_rxBuffer->head = _rxBuffer->tail;
// don't reverse this or there may be problems if the TX interrupt
// occurs after reading the value of _txBuffer->tail but before writing
// the value to _txBuffer->head.
_txBuffer->tail = _rxBuffer->head;
}
void FastSerial::write(uint8_t c)
{
int16_t i;
if (!_open) // drop bytes if not open
return;
// wait for room in the tx buffer
i = (_txBuffer->head + 1) & _txBuffer->mask;
while (i == _txBuffer->tail)
;
// add byte to the buffer
_txBuffer->bytes[_txBuffer->head] = c;
_txBuffer->head = i;
// enable the data-ready interrupt, as it may be off if the buffer is empty
*_ucsrb |= _portTxBits;
}
// Buffer management ///////////////////////////////////////////////////////////
bool FastSerial::_allocBuffer(Buffer *buffer, unsigned int size)
{
uint8_t shift;
// init buffer state
buffer->head = buffer->tail = 0;
// Compute the power of 2 greater or equal to the requested buffer size
// and then a mask to simplify wrapping operations. Using __builtin_clz
// would seem to make sense, but it uses a 256(!) byte table.
// Note that we ignore requests for more than BUFFER_MAX space.
for (shift = 1; (1U << shift) < min(_max_buffer_size, size); shift++)
;
buffer->mask = (1 << shift) - 1;
// allocate memory for the buffer - if this fails, we fail
if (buffer->bytes)
free(buffer->bytes);
buffer->bytes = (uint8_t *) malloc(buffer->mask + 1);
return (buffer->bytes != NULL);
}
void FastSerial::_freeBuffer(Buffer *buffer)
{
buffer->head = buffer->tail = 0;
buffer->mask = 0;
if (NULL != buffer->bytes) {
free(buffer->bytes);
buffer->bytes = NULL;
}
}