A serial port. More...

#include <SerialPortIODevice.h>

Inheritance diagram for nidas::core::SerialPortIODevice:

Public Member Functions
	SerialPortIODevice ()
	Constructor. More...

	SerialPortIODevice (const std::string &name)
	Constructor, passing the name of the device. More...

	~SerialPortIODevice ()
	Destructor. More...

void	open (int flags) throw (nidas::util::IOException)
	open the device. More...

void	applyTermios () throw (nidas::util::IOException)
	Apply the current Termios to an opened port. More...

nidas::util::Termios &	termios ()

int	getUsecsPerByte () const
	Calculate the transmission time of each byte from this serial port. More...

void	setRTS485 (int val) throw (nidas::util::IOException)
	Is this a RS485 half-duplex device, and if so, can the transmitter on the data system be enabled/disabled by setting/clearing RTS? If so, then RTS will be cleared when the device is opened, and set while writing to the device. More...

size_t	write (const void *buf, size_t len) throw (nidas::util::IOException)
	Write to the device. More...

int	getReadFd () const
	The file descriptor used when reading from this device. More...

int	getWriteFd () const
	The file descriptor used when writing to this device. More...

size_t	read (void *buf, size_t len) throw (nidas::util::IOException)
	Read from the device. More...

size_t	read (void *buf, size_t len, int msecTimeout) throw (nidas::util::IOException)
	Read from the device with a timeout in milliseconds. More...

void	ioctl (int request, void *buf, size_t) throw (nidas::util::IOException)

void	close () throw (nidas::util::IOException)
	close the device More...

virtual void	setName (const std::string &val)
	Set the device name to be opened for this sensor. More...

virtual const std::string &	getName () const

virtual size_t	getBytesAvailable () const throw (nidas::util::IOException)
	Return how many bytes are available to read on this IODevice. More...

Protected Attributes
nidas::util::Termios	_termios

int	_rts485

unsigned int	_usecsperbyte

int	_fd

Detailed Description

A serial port.

Constructor & Destructor Documentation

nidas::core::SerialPortIODevice::SerialPortIODevice ( )

inline

Constructor.

Does not open any actual device.

References _termios, nidas::util::Termios::setRaw(), nidas::util::Termios::setRawLength(), and nidas::util::Termios::setRawTimeout().

nidas::core::SerialPortIODevice::SerialPortIODevice ( const std::string & name )

inline

Constructor, passing the name of the device.

Does not open the device.

References _termios, nidas::util::Termios::setRaw(), nidas::util::Termios::setRawLength(), and nidas::util::Termios::setRawTimeout().

nidas::core::SerialPortIODevice::~SerialPortIODevice ( )

inline

Destructor.

Does not close the device.

Member Function Documentation

void nidas::core::SerialPortIODevice::applyTermios	(		)
throw	(	nidas::util::IOException
	)

inline

Apply the current Termios to an opened port.

References nidas::core::UnixIODevice::_fd, _termios, nidas::util::Termios::apply(), and nidas::core::IODevice::getName().

Referenced by nidas::core::SerialSensor::applyTermios().

void nidas::core::UnixIODevice::close	(		)
throw	(	nidas::util::IOException
	)

inlinevirtualinherited

close the device

Implements nidas::core::IODevice.

References nidas::core::UnixIODevice::_fd, fd, and nidas::core::IODevice::getName().

virtual size_t nidas::core::IODevice::getBytesAvailable	(		)	const
throw	(	nidas::util::IOException
	)

inlinevirtualinherited

Return how many bytes are available to read on this IODevice.

This method is only useful when ioctl FIONREAD is supported on this this IODevice, as for example with a UDP socket. It is not available, and not necessary, on most other devices, like serial ports, TCP sockets, or devices with nidas driver module support, in which case it will return an nidas::util::IOException. It is an optimization for use with UDP sockets, where after select determines that data is available on the socket file descriptor, a read will only read one datagram, even if there are more than one packet available, which would not be optimal if a sensor generated many small packets. Rather than returning back to select, we check if there are more datagrams to read. This is not necessary on other types of IODevices, where it is just a matter of using a big enough buffer to get all (or most) available data after a select.

According to man udp(7), FIONREAD will return 0 if the size of the next packet is 0. So, if select/poll indicate there is data available, one read at least should be done, just in case a sensor sends a datagram of length 0, otherwise it will never be consumed.

References err, nidas::core::IODevice::getName(), nidas::core::IODevice::getReadFd(), and nidas::core::IODevice::ioctl().

Referenced by nidas::core::DSMSensor::getBytesAvailable().

virtual const std::string& nidas::core::IODevice::getName ( ) const

inlinevirtualinherited

References nidas::core::IODevice::_devname.

Referenced by applyTermios(), nidas::core::TCPSocketIODevice::close(), nidas::core::UDPSocketIODevice::close(), nidas::core::ServerSocketIODevice::close(), nidas::core::UnixIODevice::close(), nidas::core::IODevice::getBytesAvailable(), nidas::core::SocketIODevice::ioctl(), nidas::core::ServerSocketIODevice::ioctl(), nidas::core::UnixIODevice::ioctl(), nidas::core::SocketIODevice::open(), nidas::core::ServerSocketIODevice::open(), nidas::core::UnixIODevice::open(), nidas::core::UnixIODevice::read(), and nidas::core::UnixIODevice::write().

int nidas::core::UnixIODevice::getReadFd ( ) const

inlinevirtualinherited

The file descriptor used when reading from this device.

Implements nidas::core::IODevice.

References nidas::core::UnixIODevice::_fd.

int SerialPortIODevice::getUsecsPerByte ( ) const

Calculate the transmission time of each byte from this serial port.

For RS232/485/422 serial ports is it simply calculated as (databits + stopbits + 1) / baudrate converted to microseconds. This value is used by MessageStreamScanners to guess at the time that the first byte of a buffer was sent, knowing the arrival time of that buffer of characters. In the absence of further information, this corrected transmission time is then used as the sample time.

This method checks if the underlying IODevice is a tty, returning a value of 0 usecs if it is not a tty, such as for a socket. Therefore the IODevice should exist and be open for this method to work correctly. In Sensor::open(), the IODevice is built, then opened, and then the SampleScanner is created, which is when this method should be called.

It will return 0 for socket devices.

References nidas::util::Termios::EVEN, nidas::util::Termios::NONE, nidas::util::Termios::ODD, and USECS_PER_SEC.

Referenced by nidas::core::SerialSensor::getUsecsPerByte().

int nidas::core::UnixIODevice::getWriteFd ( ) const

inlinevirtualinherited

The file descriptor used when writing to this device.

Implements nidas::core::IODevice.

References nidas::core::UnixIODevice::_fd.

void nidas::core::UnixIODevice::ioctl	(	int	request,
		void *	buf,
		size_t
	)
throw	(	nidas::util::IOException
	)

inlinevirtualinherited

Implements nidas::core::IODevice.

References nidas::core::UnixIODevice::_fd, and nidas::core::IODevice::getName().

void SerialPortIODevice::open	(	int	flags	)
throw	(	nidas::util::IOException
	)

virtual

open the device.

Implements nidas::core::IODevice.

size_t nidas::core::UnixIODevice::read	(	void *	buf,
		size_t	len
	)
throw	(	nidas::util::IOException
	)

inlinevirtualinherited

Read from the device.

Implements nidas::core::IODevice.

References nidas::core::UnixIODevice::_fd, nidas::core::IODevice::getName(), and len.

size_t UnixIODevice::read	(	void *	buf,
		size_t	len,
		int	msecTimeout
	)
throw	(	nidas::util::IOException
	)

virtualinherited

Read from the device with a timeout in milliseconds.

Implements nidas::core::IODevice.

References len, MSECS_PER_SEC, and NSECS_PER_MSEC.

virtual void nidas::core::IODevice::setName ( const std::string & val )

inlinevirtualinherited

Set the device name to be opened for this sensor.

References nidas::core::IODevice::_devname.

Referenced by nidas::core::UnixIODevice::UnixIODevice().

void SerialPortIODevice::setRTS485	(	int	val	)
throw	(	nidas::util::IOException
	)

Is this a RS485 half-duplex device, and if so, can the transmitter on the data system be enabled/disabled by setting/clearing RTS? If so, then RTS will be cleared when the device is opened, and set while writing to the device.

If is often the case that one must disable the local transmitter in order to receive characters over half-duplex 485, otherwise the transmitter clobbers the signal levels. On serial interfaces that support rs232,422 and 485 protocols, it is common that that the transmitter can be enabled/disabled with RTS from the UART when the interface is configured for 485 mode.

This RTS control of the transmitter in 485 mode is available on port 4 of Eurotech Vipers and Titans, and on all ports of the Diamond Emerald cards.

The best situation is if automatic control of RTS on 485 accesses is supported on the UART and supported for that UART in the kernel. This provides precise timing, so that the transmitter is enabled precisely while bit transmits are taking place.

Automatic RTS control is available on the Exar XR16C285x UARTS of the Eurotech Vipers and Titans. It is not available on the ST16C554 on the Diamond Emerald serial card. However, I don't see kernel support for this on Exars in the mainline kernel, even as recent as 3.8.2. Patches are floating around.

If automatic RTS control is available in the kernel, there will be ioctl macros TIOCGRS485/TIOCSRS485 in /usr/include/asm-generic/ioctls.h, and struct serial_rs485 in /usr/include/linux/serial.h. Presumably if the request is not supported on a given UART, you'll get an EINVAL.

See the kernel documentation: Documentation/serial/serial-rs485.txt

Since kernel support is not available for this on the kernels and UARTs we are using, code for the above ioctls is not yet in NIDAS.

Without hardware and kernel support for automatic RTS control with 485, we have to resort to inexact control of RTS from user space code. This will probably result in loss of data if the remote device answers back too quickly after a write to the device. Since this software control is not great, 485 is best used for read-only devices. Use 232 or 422 if you need read/write.

Referenced by nidas::core::SerialSensor::buildIODevice().

nidas::util::Termios& nidas::core::SerialPortIODevice::termios ( )

inline

References _termios.

Referenced by nidas::core::SerialSensor::applyTermios(), and nidas::core::SerialSensor::buildIODevice().