Manuel Gebele > Comedi-Lib-0.24 > Comedi::Lib

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Module Version: 0.24   Source  

NAME ^

Comedi::Lib - Perl API for Comedilib (NEW version)

VERSION ^

Version 0.24

SYNOPSIS ^

Comedi::Lib provides a Perl wrapper around the Comedilib library. This supports Perl code controlling and accessing control and measurement devices.

   use Comedi::Lib;

   # Create a Comedi::Lib object and open the Comedi device
   my $cref = Comedi::Lib->new(device => '/dev/comedi0', open_flag => 1);

   # Get the driver and board name of the device
   my $dname = $cref->get_driver_name();
   my $bname = $cref->get_board_name();
   ...
   ...
   ...
   # Close the Comedi device (optional)
   $cref->close();

DESCRIPTION ^

This module provides a Perl API for Comedilib. Comedilib is a separately distributed package containing a user-space library that provides a developer-friendly interface to the Comedi devices. This module consists of the functions that the Comedilib library provides.

TODO

I don't use XS, C::Scan or something like that, to export constants and macros to the callers name-space, as long as it's not clarified which constants and macros used for Comedilib and which for 'pure' Comedi (driver development). Both the documentation and the source code couldn't help me at all to resolve that problem.

NOTE

This module does _not_ support any ALPHA constants, macros or functions. This will be done by a separately module, anytime soon.

DEPENDENCIES ^

Comedi::Lib is dependent on the Comedilib library. Please download and install the latest version at http://www.comedi.org/. The Comedilib library _must_ be found in your library path when using this module. The library is defaultly installed in /usr/local/lib - in this case, be sure that the /usr/local/lib path is in your /etc/ld.so.conf.

Comedi::Lib also depends on the InlineX::C2XS, define and enum modules, as well as the Test::More, POSIX and Carp core modules, and the strict and warnings pragmas.

EXPORT ^

None, this is an object-oriented Perl module.

USAGE ^

CONSTANTS

This class provides a set of constants . The constants defined at this time are:

   # Comedi's major device number
   COMEDI_MAJOR

   # Maximum number of minor devices (this can be increased)
   COMEDI_NDEVICES
   
   # Number of config options in the config structure
   COMEDI_NDEVCONFOPTS

   # Length of nth chunk of firmware data
   COMEDI_DEVCONF_AUX_DATA3_LENGTH  
   COMEDI_DEVCONF_AUX_DATA2_LENGTH  
   COMEDI_DEVCONF_AUX_DATA1_LENGTH  
   COMEDI_DEVCONF_AUX_DATA0_LENGTH  
   COMEDI_DEVCONF_AUX_DATA_HI  
   COMEDI_DEVCONF_AUX_DATA_LO 
   COMEDI_DEVCONF_AUX_DATA_LENGTH

   # Max length of device and driver names
   COMEDI_NAMELEN

   # Packs and unpacks a channel/range number (see also macro section)
   CR_FLAGS_MASK
   CR_ALT_FILTER
   CR_DITHER
   CR_DEGLITCH
   CR_ALT_SOURCE
   CR_EDGE
   CR_INVERT

   # Analog ref
   AREF_GROUND
   AREF_COMMON
   AREF_DIFF
   AREF_OTHER

   # Counters
   GPCT_RESET
   GPCT_SET_SOURCE
   GPCT_SET_GATE
   GPCT_SET_DIRECTION
   GPCT_SET_OPERATION
   GPCT_ARM
   GPCT_DISARM
   GPCT_GET_INT_CLK_FRQ
   GPCT_INT_CLOCK
   GPCT_EXT_PIN
   GPCT_NO_GATE
   GPCT_UP
   GPCT_DOWN
   GPCT_HWUD
   GPCT_SIMPLE_EVENT
   GPCT_SINGLE_PERIOD
   GPCT_SINGLE_PW
   GPCT_CONT_PULSE_OUT
   GPCT_SINGLE_PULSE_OUT
   
   # Instructions
   INSN_MASK_WRITE
   INSN_MASK_READ
   INSN_MASK_SPECIAL

   INSN_READ
   INSN_WRITE
   INSN_BITS
   INSN_CONFIG
   INSN_GTOD
   INSN_WAIT
   INSN_INTTRIG

   # Trigger flags, used in comedi_trig structures
   TRIG_BOGUS
   TRIG_DITHER
   TRIG_DEGLITCH
   TRIG_CONFIG
   TRIG_WAKE_EOS
   
   # Command flags, used in comedi_cmd structures
   CMDF_PRIORITY
   TRIG_RT
   CMDF_WRITE
   TRIG_WRITE
   CMDF_RAWDATA

   COMEDI_EV_START
   COMEDI_EV_SCAN_BEGIN
   COMEDI_EV_CONVERT
   COMEDI_EV_SCAN_END
   COMEDI_EV_STOP
   TRIG_ROUND_MASK
   TRIG_ROUND_NEAREST
   TRIG_ROUND_DOWN
   TRIG_ROUND_UP
   TRIG_ROUND_UP_NEXT

   # Trigger sources
   TRIG_ANY
   TRIG_INVALID
   TRIG_NONE
   TRIG_NOW
   TRIG_FOLLOW
   TRIG_TIME
   TRIG_TIMER
   TRIG_COUNT
   TRIG_EXT
   TRIG_INT
   TRIG_OTHER

   # Subdevice flags
   SDF_BUSY
   SDF_BUSY_OWNER
   SDF_LOCKED
   SDF_LOCK_OWNER
   SDF_MAXDATA
   SDF_FLAGS
   SDF_RANGETYPE
   SDF_MODE0
   SDF_MODE1
   SDF_MODE2
   SDF_MODE3
   SDF_MODE4
   SDF_CMD
   SDF_SOFT_CALIBRATED
   SDF_CMD_WRITE
   SDF_CMD_READ
   SDF_READABLE
   SDF_WRITABLE
   SDF_WRITEABLE
   SDF_INTERNAL
   SDF_RT
   SDF_GROUND
   SDF_COMMON
   SDF_DIFF
   SDF_OTHER
   SDF_DITHER
   SDF_DEGLITCH
   SDF_MMAP
   SDF_RUNNING
   SDF_LSAMPL
   SDF_PACKED
   SDF_PWM_COUNTER
   SDF_PWM_HBRIDGE

   # Subdevice types
   COMEDI_SUBD_UNUSED
   COMEDI_SUBD_AI
   COMEDI_SUBD_AO
   COMEDI_SUBD_DI
   COMEDI_SUBD_DO
   COMEDI_SUBD_DIO
   COMEDI_SUBD_COUNTER
   COMEDI_SUBD_TIMER
   COMEDI_SUBD_MEMORY
   COMEDI_SUBD_CALIB
   COMEDI_SUBD_PROC
   COMEDI_SUBD_SERIAL
   COMEDI_SUBD_PWM

   # Configuration instructions
   INSN_CONFIG_DIO_INPUT
   INSN_CONFIG_DIO_OUTPUT
   INSN_CONFIG_DIO_OPENDRAIN
   INSN_CONFIG_ANALOG_TRIG
   INSN_CONFIG_ALT_SOURCE
   INSN_CONFIG_DIGITAL_TRIG
   INSN_CONFIG_BLOCK_SIZE
   INSN_CONFIG_TIMER_1
   INSN_CONFIG_FILTER
   INSN_CONFIG_CHANGE_NOTIFY

   COMEDI_INPUT
   COMEDI_OUTPUT
   COMEDI_OPENDRAIN

   COMEDI_UNKNOWN_SUPPORT
   COMEDI_SUPPORTED
   COMEDI_UNSUPPORTED

   # Range stuff (see also macro section)
   RF_EXTERNAL

   # Units
   UNIT_volt
   UNIT_mA
   UNIT_none

   COMEDI_MIN_SPEED

MACROS

This class provides also a set of (pseudo-)macros (implemented as a method). The macros defined at this time are:

   # Packs and unpacks a channel/range number
   CR_PACK($chan, $rng, $aref)
   CR_PACK_FLAGS($chan, $rng, $aref, $flags)
   
   # Intended only for driver development work?
   CR_CHAN($a)
   CR_RANGE($a)
   CR_AREF($a)

   # Range stuff   
   # Intended only for driver development work?
   RANGE_OFFSET($a)
   RANGE_LENGTH($a)
   
   # Intended only for driver development work?
   RF_UNIT($flags)   

Example code,

   my $chanspec = $cref->CR_PACK($chan, $rng, $aref);

FUNCTIONS

DESTROY

Close the Comedi device connected to the object.

new

Create a new Comedi::Lib object for accessing the library.

Example code,

   my $cref = Comedi::Lib->new(device => '/dev/comedi0', open_flag => 1);
close

Close a Comedi device.

Example code,

   my $retval = $cref->close();
     
   if ($retval != 0) {
      croak "Couldn't close the Comedi device";
   }

If successful, close() returns 0. On failure, -1 is returned.

open

Trigger an explicit open() call to open the Comedi device. If the device is already open, close and reopen it.

You _need_ to be root to open a Comedi device. Comedi::Lib checks that.

Example code,

   # Create a new object (don't open the device yet).
   my $cref = Comedi::Lib->new(device => "/dev/comedi1", open_flag => 0);
   ...
   ...
   ...
   # Now open the Comedi device
   $cref->open();

If successful, open() returns defined. On failure, undef is returned.

loglevel

Change Comedilib logging properties.

The default loglevel can be set by using the environment variable COMEDILIB_LOGLEVEL. The default loglevel is 1.

The meaning of the loglevels is as follows:

COMEDI_LOGLEVEL = 0

-- Comedilib prints nothing.

COMEDI_LOGLEVEL = 1

-- Comedilib prints error messages when there is a self-consistency error. (i.e., an internal bug)

COMEDI_LOGLEVEL = 2

-- Comedilib prints an error message when an invalid parameter is passed.

COMEDI_LOGLEVEL = 3

-- Comedilib prints an error message whenever an error is generated in the Comedilib library or in the C library, when called by Comedilib.

COMEDI_LOGLEVEL = 4

-- Comedilib prints a lot of junk.

Example code,

   my $previous_loglevel = $cref->loglevel($new_loglevel);
   print "Changed loglevel from $previous_loglevel to $new_loglevel\n";

This class method returns the previous loglevel.

Note: Comedilib evaluates the COMEDILIB_LOGLEVEL environment variable during open() is called. The Comedi::Lib implementation of this function allows you to set the above variable once the Comedi device is already opened.

perror

Print a Comedilib error message.

Example code,

   unless ($cref->open()) {
      $cref->perror($device);
      croak "Terminating...";
   }

The class method perror() prints an error message to stderr. The error message consists of the argument string, a colon, a space, a description of the error condition, and a new line.

strerror

Return string describing Comedilib error code.

Example code,

   unless ($cref->open()) {
      my $errnum = $cref->errno();
      my $errmsg = $cref->strerror($errnum);
      croak "An error has occurred - $errmsg";
   }

The class method strerror() returns a character string describing the Comedilib error errnum. An unrecognized error number will return a string "undefined error", or similar.

errno

Number of the last Comedilib error. This error number can be converted to a human-readable form by the methods perror() and strerror().

Example code,

   # See strerror()

The errno() class method returns an integer describing the most recent Comedilib error. This integer my be used as the errnum argument for strerror().

fileno

Integer descriptor of the Comedi device.

   my $fileno = $cref->fileno();
   print "File # of Comedi device - $fileno\n";

If successful, fileno() returns a file descriptor, or -1 on error.

get_n_subdevices

Number of subdevices

Example code,

   my $n_subdevices = $cref->get_n_subdevices();
   print "# of subdevices - $n_subdevices\n";

The class method get_n_subdevices() returns the number of subdevices belonging to the Comedi device previously opened during the Object creation or explicitly by an open() call.

get_version_code

Comedi version code.

Example code,

   my @version_code = $cref->get_version_code();
   printf("Comedi version code - %d.%d.%d\n", @version_code);

Returns the Comedi kernel module version code, or -1 on error.

get_driver_name

Comedi driver name.

Example code,

   my $driver_name = $cref->get_driver_name();
   print "Comedi driver name - $driver_name\n";

Returns a character string containing the name of the driver. This class method returns undef if there is an error.

get_board_name

Comedi device name.

Example code,

   my $board_name = $cref->get_board_name();
   print "Comedi board/device name - $board_name\n";

Returns a character string containing the name of the device. This class method returns undef if there is an error.

get_subdevice_type

Type of subdevice.

Example code,

   my $subdev_type = $cref->get_subdevice_type($subdev);
   
   if ($subdev_type == Comedi::Lib::COMEDI_SUBD_AI) {
      print "We've an analog input subdevice\n";
   }

This class method returns the subdevice type, or -1 if there is an error.

find_subdevice_by_type

Search for subdevice type.

Example code,

   my $idx = $cref->find_sundevice_by_type(Comedi::Lib::COMEDI_SUBD_DO, 0);
   croak "No digital output subdevice found\n" if $idx == -1;
   
   print "Found digital output subdevice at index - $idx\n";

If it finds a subdevice with the requested type, find_subdevice_by_type() returns its index. If there is an error, the method returns -1 and sets the appropriate error.

get_read_subdevice

Find streaming input subdevice.

Example code,

   my $streaming_input_support = $cref->get_read_subdevice();

   if ($streaming_input_support == -1) {
      print "No streaming input support available\n";
   }
   else {
      print "Comedi subdevice no. $streaming_input_support ",
            "allows streaming input\n";
   }

This class method returns the subdevice whose streaming input buffer is accessible through the previous opened device. If there is no such subdevice, -1 is returned.

get_write_subdevice

Find streaming output subdevice.

Example code,

   my $streaming_output_support = $cref->get_write_subdevice();

   if ($streaming_output_support == -1) {
      print "No streaming output support available\n";
   }
   else {
      print "Comedi subdevice no. $streaming_output_support ",
            "allows streaming output\n";
   }

This class method returns the subdevice whose streaming output buffer is accessible through the previous opened device. If there is no such subdevice, -1 is returned.

get_subdevice_flags

Properties of subdevice.

Example code,

   my $subdev_flags = $cref->get_subdevice_flags($subdev);

   if ($subdev_flags & Comedi::Lib::SDF_READABLE) {
      print "The subdevice can be read\n";
   }
   else {
      print "The subdevice can't be read\n";
   }

   if ($subdev_flags & Comedi::Lib::SDF_WRITEABLE) {
      print "The subdevice can be written\n";
   }
   else {
      print "The subdevice can't be written\n";
   }

This method returns a bitfield describing the capabilities of the specified subdevice. If there is an error, -1 is returned, and the Comedilib error value is set.

get_n_channels

Number of subdevice channels.

Example code,

   my $n_channels = $cref->get_n_channels($subdev);
   print "Analog input no. of channels - $n_channels\n";

Returns the number of channels of the subdevice with the index subdev. This method returns -1 on error.

range_is_chan_specific

Range information depends on channel.

Example code,

   my $retval = $cref->range_is_chan_specific($subdev);
   croak "An error has occurred" if $retval == -1;

   unless($retval) {
      print "The channels of the subdevice hasn't different ",
            "range information\n";
   }
   else {
      print "Each channel of the subdevice has different ",
            "range information\n";
   }

If each channel of the specified subdevice has different range information, this method returns 1. Otherwise, this method returns 0. If there is an error, -1 is returned.

maxdata_is_chan_specific

Maximum sample depends on channnel.

Example code,

   my $retval = $cref->maxdata_is_chan_specific($subdev);
   croak "An error has occurred" if $retval == -1;

   unless($retval) {
      print "The channels of the subdevice hasn't different ",
            "maximum sample values\n";
   }
   else {
      print "Each channel of the subdevice has different ",
            "maximum sample values\n";
   }

If each channel of the specified subdevice has different maximum sample values, this method returns 1. Otherwise, this method returns 0. If there is an error, -1 is returned.

get_maxdata

Maximum sample of channel.

Example code,

   # Read maxdata of analog input channel $chan
   my $maxdata = $cref->get_maxdata($subdev, $chan);
   croak "An error has occurred" unless $maxdata;

   print "Maximum data value for analog input channel $chan - $maxdata\n";

Returns the maximum valid sample value, or 0 on error.

get_n_ranges

Number of ranges of channel.

Example code,

   # Read number of ranges for analog input channel $chan
   my $n_ranges = $cref->get_n_ranges($subdev, $chan);

   if ($n_ranges == -1) {
      croak "An error has occurred";
   }

   print "Number of ranges for analog input channel $chan - $n_ranges\n";

Returns the number of ranges of the subdevice with the index subdev and the chan channel. This method returns -1 on error.

get_range

Range information of channel.

Example code,

   # Read the range specification of the analog input channel $chan
   my $range = $cref->get_range($subdev, $chan, $rng);
   croak "Cannot read range specification" unless defined $range->{min};

   # Print the minimal sample value of the given analog input channel
   print "Analog input channel $chan min sample value - $range->{min}\n";

The class method get_range() returns a hash reference that contains information that can be used to convert sample values to or from physical units. If there is an error, undef is returned.

find_range

Search for range.

Example code,

   my $rng_idx = $cref->find_range($subdev, $chan, $unit, $min, $max);
   
   if ($rng_idx == -1) {
      print "No matching range available\n"
   }
   else {
      print "Found a matching range for channel $chan at index $rng_idx\n";
   }

If a matching range is found, the index of the matching range is returned. If no matching range is available, the class method returns -1.

get_buffer_size

Streaming buffer size of subdevice.

Example code,

   my $buf_size = $cref->get_buffer_size($subdev);
   croak "An error has occurred" if $buf_size == -1;

   print "Streaming buffer size for the subdevice - $buf_size Bytes\n";

This class method returns the size -in Bytes- of the streaming buffer for the specified subdevice. On error, -1 is returned.

get_max_buffer_size

Maximum streaming buffer size.

Example code,

   my $max_size = $cref->get_max_buffer_size($subdev);
   croak "An error has occurred" if $max_size == -1;

   print "Max. streaming buffer size for the subdevice - $max_size Bytes\n";

This class method returns the maximum allowable size -in Bytes- of the streaming buffer for the specified subdevice. On error, -1 is returned.

set_buffer_size

Streaming buffer size of subdevice.

Example code,

   # First, determine the virtual memory page size (look at the Comedi docu)
   require POSIX;

   my $vmps = POSIX::sysconf(&POSIX::_SC_PAGESIZE);
   $vmps   *= 2;

   print "Trying to set the streaming buffer size to $vmps\n";

   if ($cref->set_buffer_size($subdev, $vmps) == -1) {
      print "Warning: Couldn't set new streaming buffer size\n";
   }

The set_buffer_size() class method returns the new buffer size in Bytes. On error, -1 is returned.

do_insnlist

Perform multible instructions.

Example code,

   my @insn_arr = ({
      insn      => Comedi::Lib::INSN_READ,
      n         => 2,
      data      => [0, 0],
      subdev    => 0,
      chanspec  => $cref->CR_PACK($chan, $rng, $aref)
   }, {
      insn      => Comedi::Lib::INSN_WRITE,
      n         => 1,
      data      => [255],
      subdev    => 1,
      chanspec  => $cref->CR_PACK($chan, $rng, $aref)
   });

   # Now, create a comedi_insnlist like hash reference
   my $comedi_insnlist = {
      n_insns => 2,
      insns   => [@insn_arr]
   };

   my $retval = $cref->do_insnlist($comedi_insnlist);
   croak "An error has occurred" if $retval == -1;

   print "[<1>] data (AI) - ", $insn_arr[0]->{data}[0], "\n";
   print "[<2>] data (AI) - ", $insn_arr[0]->{data}[1], "\n";

This class method returns the number of successfully completed instructions. If there is an error before the first instruction can be executed, -1 is returned.

do_insn

Perform an instruction.

Example code,

   # First, create a comedi_insn like hash reference
   my $comedi_insn = {
      insn     => Comedi::Lib::INSN_READ,
      n        => 2,
      data     => [0, 0], 
      subdev   => 0,
      chanspec => $cref->CR_PACK($chan, $rng, $aref)
   };

   my $retval = $cref->do_insn($comedi_insn);
   croak "An error has occured" if $retval == -1;

   print "[<1>] data (AI) - ", $comedi_insn->{data}[0], "\n";
   print "[<2>] data (AI) - ", $comedi_insn->{data}[1], "\n";

This class method returns the number of samples measured, which may be less than the number of requested samples. If there is an error before the first instruction can be executed, -1 is returned.

lock

Subdevice reservation.

Example code,

   my $retval = $cref->lock($subdev);
   croak "An error has occurred" if $retval == -1;

If successful, lock() returns 0. If there is an error, -1 is returned.

unlock

Subdevice reservation.

Example code,

   my $retval = $cref->unlock($subdev);
   croak "An error has occurred" if $retval == -1;

If successful, unlock() returns 0. If there is an error, -1 is returned.

data_read

Read single sample from channel.

Example code,

   my $retval = $cref->data_read($subdev, $chan, $rng, $aref, \$data);
   croak "An error hash occurred" if $retval == -1;

   print "Have read a single sample value of $data\n";

On success, data_read() returns 1 (the number of samples read). If there is an error, -1 is returned.

data_read_delayed

Read single sample from channel after delaying for specified time.

Example code,

   my $ret = $cref->data_read_delayed($subd, $chan, $rng, $aref, \$data, $ns);
   croak "An error hash occurred" if $retval == -1;

   print "Have read a single sample value of $data\n";

The return value of this class method is identical to the data_read() function.

data_read_hint

Tell driver which channel/range/aref you're going to read from next.

Example code

   my $retval = $cref->data_read_hint($subdev, $chan, $rng, $aref);
   croak "An error hash occurred" if $retval == -1;

The return value of this class method is identical to the data_read() function.

data_write

Write single sample to channel.

Example code,

   my $retval = $cref->data_write($subdev, $chan, $rng, $aref, $data);
   croak "An error hash occurred" if $retval == -1;

On success, data_write() returns 1 (the number of samples read). If there is an error, -1 is returned.

dio_config

Change input/output properties of channel.

Example code,

   # For input
   my $retval = $cref->dio_config($subdev, $chan, Comedi::Lib::COMEDI_INPUT);
   croak "An error hash occurred" if $retval == -1;

   # For output
   my $retval = $cref->dio_config($subdev, $chan, Comedi::Lib::COMEDI_INPUT);
   croak "An error hash occurred" if $retval == -1;

If successful, 1 is returned, otherwise -1.

dio_get_config

Query input/output properties of channel.

Example code,

   my $retval = $cref->dio_get_config($subdev, $chan, \$dir);
   croak "An error hash occurred" if $retval == -1;

   if ($dir == Comedi::Lib::COMEDI_INPUT) {
      print "Input direction\n";
   }
   else { # Comedi::Lib::COMEDI_OUTPUT
      print "Output direction\n";
   }

If successful, 0 is returned, otherwise -1.

dio_read

Read single bit from digital channel.

Example code,

   my $retval = $cref->data_read($subdev, $chan, \$bit);
   croak "An error has occurred" if $retval == -1;
   
   print "Have read a data value of $bit\n";

Return values and errors are the same as data_read().

dio_write

Write single bit to digital channel.

Example code,

   my $retval = $cref->data_write($subdev, $chan, $bit);
   croak "An error has occurred" if $retval == -1;

Return values and errors are the same as data_write().

dio_bitfield2

Read/Write multible digital channels.

Example code,

   my $retval = $cref->dio_bitfield2($subdev, $write_mask, \$bits, $base_ch);
   croak "An error has occurred" if $retval == -1;

   # Evaluate the $bits variable...

If successful, dio_bitfield2() returns 0. If there is an error, -1 is returned.

get_cmd_src_mask

Streaming input/output capabilities.

Note that this subroutine has no functionality as long as I have no testing device with the associated driver.

Patches or suggestions are welcome, send me an email (Subject: Comedi::Lib).

get_cmd_generic_timed

Streaming input/output capabilities.

Note that this subroutine has no functionality as long as I have no testing device with the associated driver.

Patches or suggestions are welcome, send me an email (Subject: Comedi::Lib).

cancel

Stop streaming input/output in progress.

Example code,

   # This class method is useful in combination with command()
   # and this class method is not completely implemented yet.

If successful, cancel() returns 0, otherwise -1.

command

Start streaming input/output.

Note that this subroutine has no functionality as long as I have no testing device with the associated driver.

Patches or suggestions are welcome, send me an email (Subject: Comedi::Lib).

command_test

Test streaming input/output configuration.

Note that this subroutine has no functionality as long as I have no testing device with the associated driver.

Patches or suggestions are welcome, send me an email (Subject: Comedi::Lib).

poll

Force updating of streaming buffer.

Example code,

   my $retval = $cref->poll($subdev);
   croak "An error has occurred" if $retval == -1;

If successful, this class method returns the number of additional bytes available. If there is an error, -1 is returned.

set_max_buffer_size

Streaming buffer size of subdevice.

Example code,

   my $old_buf_size = $cref->set_max_buffer_size($subdev, $max_size);
   
   if ($old_buf_size == -1) {
      croak "An error has occurred";
   }
   else {
      print "Buffer size changed from $old_buf_size to $max_size.\n";
   }

If successful, the old buffer size is returned. On error, -1 is returned.

get_buffer_contents

Streaming buffer status.

Example code,

   # This class method is useful in combination with command()
   # and this class method is not completely implemented yet.

This class method returns the number of bytes that are available in the streaming buffer. If there is an error, -1 is returned.

mark_buffer_read

Streaming buffer control.

Example code,

   # This class method is useful in combination with command()
   # and this class method is not completely implemented yet.

The mark_buffer_read() class method returns the number of bytes successfully marked as read, or -1 on error.

mark_buffer_written

Streaming buffer control.

Example code,

   # This class method is useful in combination with command()
   # and this class method is not completely implemented yet.

The mark_buffer_written() class method returns the number of bytes successfully marked as written, or -1 on error.

get_buffer_offset

Streaming buffer status.

Example code,

   # This class method is useful in combination with command()
   # and this class method is not completely implemented yet.

This class method returns the offset in bytes of the read pointer in the streaming buffer. If there is an error, -1 is returned.

AUTHOR ^

Manuel Gebele <forensixs[at]gmx.de>

SEE ALSO ^

The linux control and measurement device interface project at http://www.comedi.org.

SUPPORT & DOCUMENTATION ^

After installing, you can find documentation for this module with the perldoc command

   perldoc Comedi::Lib

or use the man command

   man Comedi::Lib

You can also look for information at:

   Search CPAN
      http://search.cpan.org/dist/Comedi-Lib

   CPAN Request Tracker
      http://rt.cpan.org/NoAuth/Bugs.html?Dist=Comedi-Lib

   AnnoCPAN, annotated CPAN documentation
      http://annocpan.org/dist/Comedi-Lib

   CPAN Ratings
      http://cpanratings.perl.org/d/Comedi-Lib

   Comedi
      http://www.comedi.org

BUGS ^

Please report any bugs or feature request to my email address, or through the web interface at http://rt.cpan.org/Public/Bug/Report.html?Queue=Comedi::Lib. I'll be notified, and then you'll automatically be notified of progess on your bug as I make changes.

COPYRIGHT & LICENSE ^

Copyright (c) 2009 Manuel Gebele

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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