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Serial Port and IO Termination

by diskcrash (Hermit)
on Jul 21, 2003 at 00:04 UTC ( #276111=snippet: print w/replies, xml ) Need Help??
Description: Greetings Hearty Monks,

From time to time I have battered my head against my favorite I/O device, the ubiquitous RS-232 Serial Port. I think I have probably wasted at least 100 days of my life (I am old...) in this endeavour. But usually I am rewarded with data victory. As was a recent case. I had built an interface for my Aware Electronics Geiger Counter (RM-70) that used a Basic Stamp IISX chip set. Every 20 seconds it would spit out an ASCII string of radiation and temperature data. I had hunted around for examples using the Device::SerialPort module and found many. Most were copies of code used to read PBX data. But it wouldn't work. Ouch. Finally, after much research I realized that - by golly - you had to terminate the IO with a new line and not a carriage return. Oddly doing a cat </dev/ttyS0 worked, which faked me out. So I added the line in the tty setup below that converts CR to NL and zap-ity-do-dah it started terminating and sending each read. Long live RS-232. Please send along any suggestions and improvements. This also probably explains why I had failed to get good reads from a cheap-o RS-232 capable DVM a few years ago.

This was done in Perl 5.8.0 under RH Linux 9.0.

Blessings of the Church and State be upon you

# Author: David Drake
# Date:   July 18, 2003
# Requirements: Device::SerialPort 0.22 (from cpan  July 2003)
# Version: 1.0
#This script is used to read a serial port to obtain data from a
#combined Geiger counter and temperature sensor.
#The Geiger Counter is an Aware Electronics RM-70 unit. Each count
#maps to one microR per hour. The RM-70 pulse output is sent to a
#Basic Stamp-IISX microcontroller. The BS2SX accumulates counts for 20
#seconds and then sends a serial data stream out of its serial port.
#The data stream goes into the input serial port on the Linux system.
#This program then tabulates the data to a log file.

use Device::SerialPort;
use Time::gmtime;

$LOGDIR    = "/home/drake/SerialPort_files";             # path to dat
+a file
$LOGFILE   = "geiger.log";              # file name to output to
$PORT      = "/dev/ttyS0";              # port to watch

# Serial Settings

#make the serial port object
#note the need to convert carriage returns to new lines to terminate e

$ob = Device::SerialPort->new ($PORT) || die "Can't Open $PORT: $!";

$ob->baudrate(9600)   || die "failed setting baudrate";
$ob->parity("none")    || die "failed setting parity";
$ob->databits(8)       || die "failed setting databits";
$ob->stty_icrnl(1)     || die "failed setting convert cr to new line" 
$ob->handshake("none") || die "failed setting handshake";

$ob->write_settings    || die "no settings";

# open the logfile, and Port

  ||die "can't open smdr file $LOGDIR/$LOGFILE for append: $SUB $!\n";

select(LOG), $| = 1;    # set nonbuffered mode, gets the chars out NOW

open(DEV, "<$PORT") || die "Cannot open $PORT: $_";

# Loop forver, logging data to the log file

while($_ = <DEV>){        # print input device to file
        $gmc = gmctime();
        print LOG $gmc," ",$_;

undef $ob;

#we are done dude
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Re: Serial Port and IO Termination
by Anonymous Monk on Mar 06, 2009 at 11:03 UTC
    Hi I tried using this for COM4 it is not wokring
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