Provided by: libdevice-serialport-perl_1.04-3build2_amd64 
NAME
Device::SerialPort - Linux/POSIX emulation of Win32::SerialPort functions.
SYNOPSIS
use Device::SerialPort qw( :PARAM :STAT 0.07 );
Constructors
# $lockfile is optional
$PortObj = new Device::SerialPort ($PortName, $quiet, $lockfile)
|| die "Can't open $PortName: $!\n";
$PortObj = start Device::SerialPort ($Configuration_File_Name)
|| die "Can't start $Configuration_File_Name: $!\n";
$PortObj = tie (*FH, 'Device::SerialPort', $Configuration_File_Name)
|| die "Can't tie using $Configuration_File_Name: $!\n";
Configuration Utility Methods
$PortObj->alias("MODEM1");
$PortObj->save($Configuration_File_Name)
|| warn "Can't save $Configuration_File_Name: $!\n";
# currently optional after new, POSIX version expected to succeed
$PortObj->write_settings;
# rereads file to either return open port to a known state
# or switch to a different configuration on the same port
$PortObj->restart($Configuration_File_Name)
|| warn "Can't reread $Configuration_File_Name: $!\n";
# "app. variables" saved in $Configuration_File, not used internally
$PortObj->devicetype('none'); # CM11, CM17, 'weeder', 'modem'
$PortObj->hostname('localhost'); # for socket-based implementations
$PortObj->hostaddr(0); # false unless specified
$PortObj->datatype('raw'); # in case an application needs_to_know
$PortObj->cfg_param_1('none'); # null string '' hard to save/restore
$PortObj->cfg_param_2('none'); # 3 spares should be enough for now
$PortObj->cfg_param_3('none'); # one may end up as a log file path
# test suite use only
@necessary_param = Device::SerialPort->set_test_mode_active(1);
# exported by :PARAM
nocarp || carp "Something fishy";
$a = SHORTsize; # 0xffff
$a = LONGsize; # 0xffffffff
$answer = yes_true("choice"); # 1 or 0
OS_Error unless ($API_Call_OK); # prints error
Configuration Parameter Methods
# most methods can be called two ways:
$PortObj->handshake("xoff"); # set parameter
$flowcontrol = $PortObj->handshake; # current value (scalar)
# The only "list context" method calls from Win32::SerialPort
# currently supported are those for baudrate, parity, databits,
# stopbits, and handshake (which only accept specific input values).
@handshake_opts = $PortObj->handshake; # permitted choices (list)
# similar
$PortObj->baudrate(9600);
$PortObj->parity("odd");
$PortObj->databits(8);
$PortObj->stopbits(1); # POSIX does not support 1.5 stopbits
# these are essentially dummies in POSIX implementation
# the calls exist to support compatibility
$PortObj->buffers(4096, 4096); # returns (4096, 4096)
@max_values = $PortObj->buffer_max; # returns (4096, 4096)
$PortObj->reset_error; # returns 0
# true/false parameters (return scalar context only)
# parameters exist, but message processing not yet fully implemented
$PortObj->user_msg(ON); # built-in instead of warn/die above
$PortObj->error_msg(ON); # translate error bitmasks and carp
$PortObj->parity_enable(F); # faults during input
$PortObj->debug(0);
# true/false capabilities (read only)
# most are just constants in the POSIX case
$PortObj->can_baud; # 1
$PortObj->can_databits; # 1
$PortObj->can_stopbits; # 1
$PortObj->can_dtrdsr; # 1
$PortObj->can_handshake; # 1
$PortObj->can_parity_check; # 1
$PortObj->can_parity_config; # 1
$PortObj->can_parity_enable; # 1
$PortObj->can_rlsd; # 0 currently
$PortObj->can_16bitmode; # 0 Win32-specific
$PortObj->is_rs232; # 1
$PortObj->is_modem; # 0 Win32-specific
$PortObj->can_rtscts; # 1
$PortObj->can_xonxoff; # 1
$PortObj->can_xon_char; # 1 use stty
$PortObj->can_spec_char; # 0 use stty
$PortObj->can_interval_timeout; # 0 currently
$PortObj->can_total_timeout; # 1 currently
$PortObj->can_ioctl; # automatically detected
$PortObj->can_status; # automatically detected
$PortObj->can_write_done; # automatically detected
$PortObj->can_modemlines; # automatically detected
$PortObj->can_wait_modemlines;# automatically detected
$PortObj->can_intr_count; # automatically detected
$PortObj->can_arbitrary_baud; # automatically detected
Operating Methods
($count_in, $string_in) = $PortObj->read($InBytes);
warn "read unsuccessful\n" unless ($count_in == $InBytes);
$count_out = $PortObj->write($output_string);
warn "write failed\n" unless ($count_out);
warn "write incomplete\n" if ( $count_out != length($output_string) );
if ($string_in = $PortObj->input) { PortObj->write($string_in); }
# simple echo with no control character processing
if ($PortObj->can_wait_modemlines) {
$rc = $PortObj->wait_modemlines( MS_RLSD_ON );
if (!$rc) { print "carrier detect changed\n"; }
}
if ($PortObj->can_modemlines) {
$ModemStatus = $PortObj->modemlines;
if ($ModemStatus & $PortObj->MS_RLSD_ON) { print "carrier detected\n"; }
}
if ($PortObj->can_intr_count) {
$count = $PortObj->intr_count();
print "got $count interrupts\n";
}
if ($PortObj->can_arbitrary_baud) {
print "this port can set arbitrary baud rates\n";
}
($BlockingFlags, $InBytes, $OutBytes, $ErrorFlags) = $PortObj->status;
# same format for compatibility. Only $InBytes and $OutBytes are
# currently returned (on linux). Others are 0.
# Check return value of "can_status" to see if this call is valid.
($done, $count_out) = $PortObj->write_done(0);
# POSIX defaults to background write. Currently $count_out always 0.
# $done set when hardware finished transmitting and shared line can
# be released for other use. Ioctl may not work on all OSs.
# Check return value of "can_write_done" to see if this call is valid.
$PortObj->write_drain; # POSIX alternative to Win32 write_done(1)
# set when software is finished transmitting
$PortObj->purge_all;
$PortObj->purge_rx;
$PortObj->purge_tx;
# controlling outputs from the port
$PortObj->dtr_active(T); # sends outputs direct to hardware
$PortObj->rts_active(Yes); # return status of ioctl call
# return undef on failure
$PortObj->pulse_break_on($milliseconds); # off version is implausible
$PortObj->pulse_rts_on($milliseconds);
$PortObj->pulse_rts_off($milliseconds);
$PortObj->pulse_dtr_on($milliseconds);
$PortObj->pulse_dtr_off($milliseconds);
# sets_bit, delays, resets_bit, delays
# returns undef if unsuccessful or ioctls not implemented
$PortObj->read_const_time(100); # const time for read (milliseconds)
$PortObj->read_char_time(5); # avg time between read char
$milliseconds = $PortObj->get_tick_count;
Methods used with Tied FileHandles
$PortObj = tie (*FH, 'Device::SerialPort', $Configuration_File_Name)
|| die "Can't tie: $!\n"; ## TIEHANDLE ##
print FH "text"; ## PRINT ##
$char = getc FH; ## GETC ##
syswrite FH, $out, length($out), 0; ## WRITE ##
$line = <FH>; ## READLINE ##
@lines = <FH>; ## READLINE ##
printf FH "received: %s", $line; ## PRINTF ##
read (FH, $in, 5, 0) or die "$!"; ## READ ##
sysread (FH, $in, 5, 0) or die "$!"; ## READ ##
close FH || warn "close failed"; ## CLOSE ##
undef $PortObj;
untie *FH; ## DESTROY ##
$PortObj->linesize(10); # with READLINE
$PortObj->lastline("_GOT_ME_"); # with READLINE, list only
## with PRINT and PRINTF, return previous value of separator
$old_ors = $PortObj->output_record_separator("RECORD");
$old_ofs = $PortObj->output_field_separator("COMMA");
Destructors
$PortObj->close || warn "close failed";
# release port to OS - needed to reopen
# close will not usually DESTROY the object
# also called as: close FH || warn "close failed";
undef $PortObj;
# preferred unless reopen expected since it triggers DESTROY
# calls $PortObj->close but does not confirm success
# MUST precede untie - do all three IN THIS SEQUENCE before re-tie.
untie *FH;
Methods for I/O Processing
$PortObj->are_match("text", "\n"); # possible end strings
$PortObj->lookclear; # empty buffers
$PortObj->write("Feed Me:"); # initial prompt
$PortObj->is_prompt("More Food:"); # not implemented
my $gotit = "";
until ("" ne $gotit) {
$gotit = $PortObj->lookfor; # poll until data ready
die "Aborted without match\n" unless (defined $gotit);
sleep 1; # polling sample time
}
printf "gotit = %s\n", $gotit; # input BEFORE the match
my ($match, $after, $pattern, $instead) = $PortObj->lastlook;
# input that MATCHED, input AFTER the match, PATTERN that matched
# input received INSTEAD when timeout without match
printf "lastlook-match = %s -after = %s -pattern = %s\n",
$match, $after, $pattern;
$gotit = $PortObj->lookfor($count); # block until $count chars received
$PortObj->are_match("-re", "pattern", "text");
# possible match strings: "pattern" is a regular expression,
# "text" is a literal string
DESCRIPTION
This module provides an object-based user interface essentially identical to the one
provided by the Win32::SerialPort module.
Initialization
The primary constructor is new with either a PortName, or a Configuretion File specified.
With a PortName, this will open the port and create the object. The port is not yet ready
for read/write access. First, the desired parameter settings must be established. Since
these are tuning constants for an underlying hardware driver in the Operating System, they
are all checked for validity by the methods that set them. The write_settings method
updates the port (and will return True under POSIX). Ports are opened for binary
transfers. A separate "binmode" is not needed.
$PortObj = new Device::SerialPort ($PortName, $quiet, $lockfile)
|| die "Can't open $PortName: $!\n";
The $quiet parameter is ignored and is only there for compatibility with
Win32::SerialPort. The $lockfile parameter is optional. It will attempt to create a file
(containing just the current process id) at the location specified. This file will be
automatically deleted when the $PortObj is no longer used (by DESTROY). You would usually
request $lockfile with $quiet true to disable messages while attempting to obtain
exclusive ownership of the port via the lock. Lockfiles are experimental in Version 0.07.
They are intended for use with other applications. No attempt is made to resolve port
aliases (/dev/modem == /dev/ttySx) or to deal with login processes such as getty and
uugetty.
Using a Configuration File with new or by using second constructor, start, scripts can be
simplified if they need a constant setup. It executes all the steps from new to
write_settings based on a previously saved configuration. This constructor will return
"undef" on a bad configuration file or failure of a validity check. The returned object is
ready for access. This is new and experimental for Version 0.055.
$PortObj2 = start Device::SerialPort ($Configuration_File_Name)
|| die;
The third constructor, tie, will combine the start with Perl's support for tied
FileHandles (see perltie). Device::SerialPort will implement the complete set of methods:
TIEHANDLE, PRINT, PRINTF, WRITE, READ, GETC, READLINE, CLOSE, and DESTROY. Tied FileHandle
support is new with Version 0.04 and the READ and READLINE methods were added in Version
0.06. In "scalar context", READLINE sets stty_icanon to do character processing and calls
lookfor. It restores stty_icanon after the read. In "list context", READLINE does
Canonical (line) reads if stty_icanon is set or calls streamline if it is not.
(stty_icanon is not altered). The streamline choice allows duplicating the operation of
Win32::SerialPort for cross-platform scripts.
The implementation attempts to mimic STDIN/STDOUT behaviour as closely as possible: calls
block until done and data strings that exceed internal buffers are divided transparently
into multiple calls. In Version 0.06, the output separators $, and "$\" are also applied
to PRINT if set. The output_record_separator and output_field_separator methods can set
Port-FileHandle-Specific versions of $, and "$\" if desired. Since PRINTF is treated
internally as a single record PRINT, "$\" will be applied. Output separators are not
applied to WRITE (called as "syswrite FH, $scalar, $length, [$offset]"). The
input_record_separator $/ is not explicitly supported - but an identical function can be
obtained with a suitable are_match setting.
$PortObj2 = tie (*FH, 'Device::SerialPort', $Configuration_File_Name)
|| die;
The tied FileHandle methods may be combined with the Device::SerialPort methods for read,
input, and write as well as other methods. The typical restrictions against mixing print
with syswrite do not apply. Since both (tied) read and sysread call the same "$ob->READ"
method, and since a separate "$ob->read" method has existed for some time in
Device::SerialPort, you should always use sysread with the tied interface (when it is
implemented).
Certain parameters SHOULD be set before executing write_settings. Others will attempt to
deduce defaults from the hardware or from other parameters. The Required parameters are:
baudrate
Any legal value.
parity One of the following: "none", "odd", "even".
By default, incoming parity is not checked. This mimics the behavior of most
terminal programs (like "minicom"). If you need parity checking enabled, please
use the "stty_inpck" and "stty_istrip" functions.
databits
An integer from 5 to 8.
stopbits
Legal values are 1 and 2.
handshake
One of the following: "none", "rts", "xoff".
Some individual parameters (eg. baudrate) can be changed after the initialization is
completed. These will be validated and will update the serial driver as required. The save
method will write the current parameters to a file that start, tie, and restart can use to
reestablish a functional setup.
$PortObj = new Win32::SerialPort ($PortName, $quiet)
|| die "Can't open $PortName: $^E\n"; # $quiet is optional
$PortObj->user_msg(ON);
$PortObj->databits(8);
$PortObj->baudrate(9600);
$PortObj->parity("none");
$PortObj->stopbits(1);
$PortObj->handshake("rts");
$PortObj->write_settings || undef $PortObj;
$PortObj->save($Configuration_File_Name);
$PortObj->baudrate(300);
$PortObj->restart($Configuration_File_Name); # back to 9600 baud
$PortObj->close || die "failed to close";
undef $PortObj; # frees memory back to perl
Configuration Utility Methods
Use alias to convert the name used by "built-in" messages.
$PortObj->alias("MODEM1");
Starting in Version 0.07, a number of Application Variables are saved in
$Configuration_File. These parameters are not used internally. But methods allow setting
and reading them. The intent is to facilitate the use of separate configuration scripts to
create the files. Then an application can use start as the Constructor and not bother with
command line processing or managing its own small configuration file. The default values
and number of parameters is subject to change.
$PortObj->devicetype('none');
$PortObj->hostname('localhost'); # for socket-based implementations
$PortObj->hostaddr(0); # a "false" value
$PortObj->datatype('raw'); # 'record' is another possibility
$PortObj->cfg_param_1('none');
$PortObj->cfg_param_2('none'); # 3 spares should be enough for now
$PortObj->cfg_param_3('none');
Configuration and Capability Methods
The Win32 Serial Comm API provides extensive information concerning the capabilities and
options available for a specific port (and instance). This module will return suitable
responses to facilitate porting code from that environment.
The get_tick_count method is a clone of the Win32::GetTickCount() function. It matches a
corresponding method in Win32::CommPort. It returns time in milliseconds - but can be
used in cross-platform scripts.
Binary selections will accept as true any of the following: "("YES", "Y", "ON", "TRUE",
"T", "1", 1)" (upper/lower/mixed case) Anything else is false.
There are a large number of possible configuration and option parameters. To facilitate
checking option validity in scripts, most configuration methods can be used in two
different ways:
method called with an argument
The parameter is set to the argument, if valid. An invalid argument returns false
(undef) and the parameter is unchanged. The function will also carp if $user_msg
is true. The port will be updated immediately if allowed (an automatic
write_settings is called).
method called with no argument in scalar context
The current value is returned. If the value is not initialized either directly or
by default, return "undef" which will parse to false. For binary selections
(true/false), return the current value. All current values from "multivalue"
selections will parse to true.
method called with no argument in list context
Methods which only accept a limited number of specific input values return a list
consisting of all acceptable choices. The null list "(undef)" will be returned for
failed calls in list context (e.g. for an invalid or unexpected argument). Only
the baudrate, parity, databits, stopbits, and handshake methods currently support
this feature.
Operating Methods
Version 0.04 adds pulse methods for the RTS, BREAK, and DTR bits. The pulse methods assume
the bit is in the opposite state when the method is called. They set the requested state,
delay the specified number of milliseconds, set the opposite state, and again delay the
specified time. These methods are designed to support devices, such as the X10
"FireCracker" control and some modems, which require pulses on these lines to signal
specific events or data. Timing for the active part of pulse_break_on is handled by
POSIX::tcsendbreak(0), which sends a 250-500 millisecond BREAK pulse. It is NOT guaranteed
to block until done.
$PortObj->pulse_break_on($milliseconds);
$PortObj->pulse_rts_on($milliseconds);
$PortObj->pulse_rts_off($milliseconds);
$PortObj->pulse_dtr_on($milliseconds);
$PortObj->pulse_dtr_off($milliseconds);
In Version 0.05, these calls and the rts_active and dtr_active calls verify the parameters
and any required ioctl constants, and return "undef" unless the call succeeds. You can use
the can_ioctl method to see if the required constants are available. On Version 0.04, the
module would not load unless asm/termios.ph was found at startup.
Stty Shortcuts
Version 0.06 adds primitive methods to modify port parameters that would otherwise require
a "system("stty...");" command. These act much like the identically-named methods in
Win32::SerialPort. However, they are initialized from "current stty settings" when the
port is opened rather than from defaults. And like stty settings, they are passed to the
serial driver and apply to all operations rather than only to I/O processed via the
lookfor method or the tied FileHandle methods. Each returns the current setting for the
parameter. There are no "global" or "combination" parameters - you still need
"system("stty...")" for that.
The methods which handle CHAR parameters set and return values as "ord(CHAR)". This
corresponds to the settings in the POSIX termios cc_field array. You are unlikely to
actually want to modify most of these. They reflect the special characters which can be
set by stty.
$PortObj->is_xon_char($num_char); # VSTART (stty start=.)
$PortObj->is_xoff_char($num_char); # VSTOP
$PortObj->is_stty_intr($num_char); # VINTR
$PortObj->is_stty_quit($num_char); # VQUIT
$PortObj->is_stty_eof($num_char); # VEOF
$PortObj->is_stty_eol($num_char); # VEOL
$PortObj->is_stty_erase($num_char); # VERASE
$PortObj->is_stty_kill($num_char); # VKILL
$PortObj->is_stty_susp($num_char); # VSUSP
Binary settings supported by POSIX will return 0 or 1. Several parameters settable by stty
do not yet have shortcut methods. Contact me if you need one that is not supported. These
are the common choices. Try "man stty" if you are not sure what they do.
$PortObj->stty_echo;
$PortObj->stty_echoe;
$PortObj->stty_echok;
$PortObj->stty_echonl;
$PortObj->stty_ignbrk;
$PortObj->stty_istrip;
$PortObj->stty_inpck;
$PortObj->stty_parmrk;
$PortObj->stty_ignpar;
$PortObj->stty_icrnl;
$PortObj->stty_igncr;
$PortObj->stty_inlcr;
$PortObj->stty_opost;
$PortObj->stty_isig;
$PortObj->stty_icanon;
The following methods require successfully loading ioctl constants. They will return
"undef" if the needed constants are not found. But the method calls may still be used
without syntax errors or warnings even in that case.
$PortObj->stty_ocrlf;
$PortObj->stty_onlcr;
$PortObj->stty_echoke;
$PortObj->stty_echoctl;
Lookfor and I/O Processing
Some communications programs have a different need - to collect (or discard) input until a
specific pattern is detected. For lines, the pattern is a line-termination. But there are
also requirements to search for other strings in the input such as "username:" and
"password:". The lookfor method provides a consistent mechanism for solving this problem.
It searches input character-by-character looking for a match to any of the elements of an
array set using the are_match method. It returns the entire input up to the match pattern
if a match is found. If no match is found, it returns "" unless an input error or abort is
detected (which returns undef).
Unlike Win32::SerialPort, lookfor does not handle backspace, echo, and other character
processing. It expects the serial driver to handle those and to be controlled via stty.
For interacting with humans, you will probably want stty_icanon(1) during lookfor to
obtain familiar command-line response. The actual match and the characters after it (if
any) may also be viewed using the lastlook method. It also adopts the convention from
Expect.pm that match strings are literal text (tested using index) unless preceded in the
are_match list by a "-re", entry. The default are_match list is "("\n")", which matches
complete lines.
my ($match, $after, $pattern, $instead) = $PortObj->lastlook;
# input that MATCHED, input AFTER the match, PATTERN that matched
# input received INSTEAD when timeout without match ("" if match)
$PortObj->are_match("text1", "-re", "pattern", "text2");
# possible match strings: "pattern" is a regular expression,
# "text1" and "text2" are literal strings
Everything in lookfor is still experimental. Please let me know if you use it (or can't
use it), so I can confirm bug fixes don't break your code. For literal strings, $match
and $pattern should be identical. The $instead value returns the internal buffer tested by
the match logic. A successful match or a lookclear resets it to "" - so it is only useful
for error handling such as timeout processing or reporting unexpected responses.
The lookfor method is designed to be sampled periodically (polled). Any characters after
the match pattern are saved for a subsequent lookfor. Internally, lookfor is implemented
using the nonblocking input method when called with no parameter. If called with a count,
lookfor calls "$PortObj->read(count)" which blocks until the read is Complete or a Timeout
occurs. The blocking alternative should not be used unless a fault time has been defined
using read_interval, read_const_time, and read_char_time. It exists mostly to support the
tied FileHandle functions sysread, getc, and <FH>. When stty_icanon is active, even the
non-blocking calls will not return data until the line is complete.
The internal buffers used by lookfor may be purged by the lookclear method (which also
clears the last match). For testing, lookclear can accept a string which is "looped back"
to the next input. This feature is enabled only when set_test_mode_active(1). Normally,
lookclear will return "undef" if given parameters. It still purges the buffers and
last_match in that case (but nothing is "looped back"). You will want stty_echo(0) when
exercising loopback.
The matchclear method is designed to handle the "special case" where the match string is
the first character(s) received by lookfor. In this case, "$lookfor_return == """, lookfor
does not provide a clear indication that a match was found. The matchclear returns the
same $match that would be returned by lastlook and resets it to "" without resetting any
of the other buffers. Since the lookfor already searched through the match, matchclear is
used to both detect and step-over "blank" lines.
The character-by-character processing used by lookfor is fine for interactive activities
and tasks which expect short responses. But it has too much "overhead" to handle fast data
streams.There is also a streamline method which is a fast, line-oriented alternative with
just pattern searching. Since streamline uses the same internal buffers, the lookclear,
lastlook, are_match, and matchclear methods act the same in both cases. In fact, calls to
streamline and lookfor can be interleaved if desired (e.g. an interactive task that starts
an upload and returns to interactive activity when it is complete).
There are two additional methods for supporting "list context" input: lastline sets an
"end_of_file" Regular Expression, and linesize permits changing the "packet size" in the
blocking read operation to allow tuning performance to data characteristics. These two
only apply during READLINE. The default for linesize is 1. There is no default for the
lastline method.
The Regular Expressions set by are_match and lastline will be pre-compiled using the qr//
construct on Perl 5.005 and higher. This doubled lookfor and streamline speed in my tests
with Regular Expressions - but actual improvements depend on both patterns and input data.
The functionality of lookfor includes a limited subset of the capabilities found in Austin
Schutz's Expect.pm for Unix (and Tcl's expect which it resembles). The "$before, $match,
$pattern, and $after" return values are available if someone needs to create an "expect"
subroutine for porting a script. When using multiple patterns, there is one important
functional difference: Expect.pm looks at each pattern in turn and returns the first match
found; lookfor and streamline test all patterns and return the one found earliest in the
input if more than one matches.
Exports
Nothing is exported by default. The following tags can be used to have large sets of
symbols exported:
:PARAM
Utility subroutines and constants for parameter setting and test:
LONGsize SHORTsize nocarp yes_true
OS_Error
:STAT
The Constants named BM_* and CE_* are omitted. But the modem status (MS_*) Constants
are defined for possible use with modemlines and wait_modemlines. They are assigned to
corresponding functions, but the bit position will be different from that on Win32.
Which incoming bits are active:
MS_CTS_ON - Clear to send
MS_DSR_ON - Data set ready
MS_RING_ON - Ring indicator
MS_RLSD_ON - Carrier detected
MS_RTS_ON - Request to send (might not exist on Win32)
MS_DTR_ON - Data terminal ready (might not exist on Win32)
If you want to write more POSIX-looking code, you can use the constants seen there,
instead of the Win32 versions:
TIOCM_CTS, TIOCM_DSR, TIOCM_RI, TIOCM_CD, TIOCM_RTS, and TIOCM_DTR
Offsets into the array returned by status:
ST_BLOCK ST_INPUT ST_OUTPUT ST_ERROR
:ALL
All of the above. Except for the test suite, there is not really a good reason to do
this.
PINOUT
Here is a handy pinout map, showing each line and signal on a standard DB9 connector:
1 DCD Data Carrier Detect
2 RD Receive Data
3 TD Transmit Data
4 DTR Data Terminal Ready
5 SG Signal Ground
6 DSR Data Set Ready
7 RTS Request to Send
8 CTS Clear to Send
9 RI Ring Indicator
NOTES
The object returned by new is NOT a Filehandle. You will be disappointed if you try to use
it as one.
e.g. the following is WRONG!!
print $PortObj "some text";
This module uses POSIX termios extensively. Raw API calls are very unforgiving. You will
certainly want to start perl with the -w switch. If you can, use strict as well. Try to
ferret out all the syntax and usage problems BEFORE issuing the API calls (many of which
modify tuning constants in hardware device drivers....not where you want to look for
bugs).
With all the options, this module needs a good tutorial. It doesn't have one yet.
EXAMPLE
It is recommended to always use "read(255)" due to some unexpected behavior with the
termios under some operating systems (Linux and Solaris at least). To deal with this, a
routine is usually needed to read from the serial port until you have what you want. This
is a quick example of how to do that:
my $port=Device::SerialPort->new("/dev/ttyS0");
my $STALL_DEFAULT=10; # how many seconds to wait for new input
my $timeout=$STALL_DEFAULT;
$port->read_char_time(0); # don't wait for each character
$port->read_const_time(1000); # 1 second per unfulfilled "read" call
my $chars=0;
my $buffer="";
while ($timeout>0) {
my ($count,$saw)=$port->read(255); # will read _up to_ 255 chars
if ($count > 0) {
$chars+=$count;
$buffer.=$saw;
# Check here to see if what we want is in the $buffer
# say "last" if we find it
}
else {
$timeout--;
}
}
if ($timeout==0) {
die "Waited $STALL_DEFAULT seconds and never saw what I wanted\n";
}
PORTING
For a serial port to work under Unix, you need the ability to do several types of
operations. With POSIX, these operations are implemented with a set of "tc*" functions.
However, not all Unix systems follow this correctly. In those cases, the functions
change, but the variables used as parameters generally turn out to be the same.
Get/Set RTS
This is only available through the bit-set(TIOCMBIS)/bit-clear(TIOCMBIC) ioctl
function using the RTS value(TIOCM_RTS).
ioctl($handle,$on ? $TIOCMBIS : $TIOCMBIC, $TIOCM_RTS);
Get/Set DTR
This is available through the bit-set(TIOCMBIS)/bit-clear(TIOCMBIC) ioctl function
using the DTR value(TIOCM_DTR)
ioctl($handle,$on ? $TIOCMBIS : $TIOCMBIC, $TIOCM_DTR);
or available through the DTRSET/DTRCLEAR ioctl functions, if they exist.
ioctl($handle,$on ? $TIOCSDTR : $TIOCCDTR, 0);
Get modem lines
To read Clear To Send (CTS), Data Set Ready (DSR), Ring Indicator (RING), and Carrier
Detect (CD/RLSD), the TIOCMGET ioctl function must be used.
ioctl($handle, $TIOCMGET, $status);
To decode the individual modem lines, some bits have multiple possible constants:
Clear To Send (CTS)
TIOCM_CTS
Data Set Ready (DSR)
TIOCM_DSR
Ring Indicator (RING)
TIOCM_RNG TIOCM_RI
Carrier Detect (CD/RLSD)
TIOCM_CAR TIOCM_CD
Get Buffer Status
To get information about the state of the serial port input and output buffers, the
TIOCINQ and TIOCOUTQ ioctl functions must be used. I'm not totally sure what is
returned by these functions across all Unix systems. Under Linux, it is the integer
number of characters in the buffer.
ioctl($handle,$in ? $TIOCINQ : $TIOCOUTQ, $count);
$count = unpack('i',$count);
Get Line Status
To get information about the state of the serial transmission line (to see if a write
has made its way totally out of the serial port buffer), the TIOCSERGETLSR ioctl
function must be used. Additionally, the "Get Buffer Status" methods must be
functioning, as well as having the first bit of the result set (Linux is TIOCSER_TEMT,
others unknown, but we've been using TIOCM_LE even though that should be returned from
the TIOCMGET ioctl).
ioctl($handle,$TIOCSERGETLSR, $status);
$done = (unpack('i', $status) & $TIOCSER_TEMT);
Set Flow Control
Some Unix systems require special TCGETX/TCSETX ioctls functions and the
CTSXON/RTSXOFF constants to turn on and off CTS/RTS "hard" flow control instead of
just using the normal POSIX tcsetattr calls.
ioctl($handle, $TCGETX, $flags);
@bytes = unpack('SSSS',$flags);
$bytes[0] = $on ? ($CTSXON | $RTSXOFF) : 0;
$flags = pack('SSSS',@bytes);
ioctl($handle, $TCSETX, $flags);
KNOWN LIMITATIONS
The current version of the module has been tested with Perl 5.003 and above. It was
initially ported from Win32 and was designed to be used without requiring a compiler or
using XS. Since everything is (sometimes convoluted but still pure) Perl, you can fix
flaws and change limits if required. But please file a bug report if you do.
The read method, and tied methods which call it, currently can use a fixed timeout which
approximates behavior of the Win32::SerialPort read_const_time and read_char_time methods.
It is used internally by select. If the timeout is set to zero, the read call will return
immediately. A read larger than 255 bytes will be split internally into 255-byte POSIX
calls due to limitations of select and VMIN. The timeout is reset for each 255-byte
segment. Hence, for large reads, use a read_const_time suitable for a 255-byte read. All
of this is expeimental in Version 0.055.
$PortObj->read_const_time(500); # 500 milliseconds = 0.5 seconds
$PortObj->read_char_time(5); # avg time between read char
The timing model defines the total time allowed to complete the operation. A fixed
overhead time is added to the product of bytes and per_byte_time.
Read_Total = read_const_time + (read_char_time * bytes_to_read)
Write timeouts and read_interval timeouts are not currently supported.
On some machines, reads larger than 4,096 bytes may be truncated at 4,096, regardless of
the read size or read timing settings used. In this case, try turning on or increasing the
inter-character delay on your serial device. Also try setting the read size to
$PortObj->read(1) or $PortObj->read(255)
and performing multiple reads until the transfer is completed.
BUGS
See the limitations about lockfiles. Experiment if you like.
With all the currently unimplemented features, we don't need any more. But there probably
are some.
Please send comments and bug reports to kees@outflux.net.
Win32::SerialPort & Win32API::CommPort
Win32::SerialPort Functions Not Currently Supported
$LatchErrorFlags = $PortObj->reset_error;
$PortObj->read_interval(100); # max time between read char
$PortObj->write_char_time(5);
$PortObj->write_const_time(100);
Functions Handled in a POSIX system by "stty"
xon_limit xoff_limit xon_char xoff_char
eof_char event_char error_char stty_intr
stty_quit stty_eof stty_eol stty_erase
stty_kill stty_clear is_stty_clear stty_bsdel
stty_echoke stty_echoctl stty_ocrnl stty_onlcr
Win32::SerialPort Functions Not Ported to POSIX
transmit_char
Win32API::CommPort Functions Not Ported to POSIX
init_done fetch_DCB update_DCB initialize
are_buffers are_baudrate are_handshake are_parity
are_databits are_stopbits is_handshake xmit_imm_char
is_baudrate is_parity is_databits is_write_char_time
debug_comm is_xon_limit is_xoff_limit is_read_const_time
suspend_tx is_eof_char is_event_char is_read_char_time
is_read_buf is_write_buf is_buffers is_read_interval
is_error_char resume_tx is_stopbits is_write_const_time
is_binary is_status write_bg is_parity_enable
is_modemlines read_bg read_done break_active
xoff_active is_read_buf is_write_buf xon_active
"raw" Win32 API Calls and Constants
A large number of Win32-specific elements have been omitted. Most of these are only
available in Win32::SerialPort and Win32API::CommPort as optional Exports. The list
includes the following:
:RAW
The API Wrapper Methods and Constants used only to support them including PURGE_*,
SET*, CLR*, EV_*, and ERROR_IO*
:COMMPROP
The Constants used for Feature and Properties Detection including BAUD_*, PST_*,
PCF_*, SP_*, DATABITS_*, STOPBITS_*, PARITY_*, and COMMPROP_INITIALIZED
:DCB
The constants for the Win32 Device Control Block including CBR_*, DTR_*, RTS_*,
*PARITY, *STOPBIT*, and FM_*
Compatibility
This code implements the functions required to support the MisterHouse Home Automation
software by Bruce Winter. It does not attempt to support functions from Win32::SerialPort
such as stty_emulation that already have POSIX implementations or to replicate Win32
idosyncracies. However, the supported functions are intended to clone the equivalent
functions in Win32::SerialPort and Win32API::CommPort. Any discrepancies or omissions
should be considered bugs and reported to the maintainer.
AUTHORS
Based on Win32::SerialPort.pm, Version 0.8, by Bill Birthisel
Ported to linux/POSIX by Joe Doss for MisterHouse
Ported to Solaris/POSIX by Kees Cook for Sendpage
Ported to BSD/POSIX by Kees Cook
Ported to Perl XS by Kees Cook
Currently maintained by:
Kees Cook, kees@outflux.net, http://outflux.net/
SEE ALSO
Win32API::CommPort
Win32::SerialPort
perltoot - Tom Christiansen's Object-Oriented Tutorial
COPYRIGHT
Copyright (C) 1999, Bill Birthisel. All rights reserved.
Copyright (C) 2000-2007, Kees Cook. All rights reserved.
This module is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.