I have fiddled some more with this serial logging. I'm ultimately trying to log the smdr output from a telephone switchboard (PBX), but I seem to be getting only intermittent success. My poll currently looks like this: 
for(;;){
        my $result=$PortObj->input;
        if($result =~ m/foo/){
                $count++;
                my $query="INSERT INTO logs(cl_date, cl_dialled) value
+s(now(),'$count')";
                my $clsth=&db_query($query);
        }
}

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In this experiment I am then sending strings down the serial connection from the other box with: 
bash-2.05b# echo "foo" >> /dev/ttyS0
bash-2.05b# echo "foo" >> /dev/ttyS0
bash-2.05b# echo "foo" >> /dev/ttyS0

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heh - you get the idea.. However, there seems to be some mad entropy behind whether or not I detect anything at the logging end - If I sent 4 lines, I might only get 1 or 2 new rows in the databse - then perhaps I'll send 8 lines and get nothing, so then I'll restart the logger and send 5 lines.. and I get 3 new entries in the database... What I'm trying to say is that it's totally random whether or not the text gets picked up at the other end. I guess I generally manage to log 10-20% of the strings that get sent down.

For info, here is the result from stty on /dev/ttyS0 - I also turned on IGNBRK. 
root@alexis:/export/serial/# stty -a < /dev/ttyS0
speed 9600 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; 
+eol2 = <undef>; start = ^Q; stop = ^S; susp = ^Z;
rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr -icrnl -i
+xon -ixoff -iuclc -ixany -imaxbel
-opost -olcuc -ocrnl -onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 
+bs0 vt0 ff0
-isig -icanon -iexten -echo -echoe -echok -echonl -noflsh -xcase -tost
+op -echoprt -echoctl -echoke

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now, I wonder if there is some way that Device::SerialPort can be made to detect that Data is ready to send, rather than just polling - am I going about this the wrong way?

thanks for your help,
christo :)

In reply to poll on serial device fails intermittently by planet_guru

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