Latest update: Hi all, It's not the negative values that is throwing it off, rather the ff (Ascii chr 255) that the Telnet.pm can't seem to send! Can anyone advise me how can I do this? Thanks

Hi all,

I'm having problems with Telnet.pm and negative values. For some unknown reason, the reply in the buffer seems to be dropping characters, even a send doesn't seem to be sending correctly as the value on the controller did not respond. However, using a simulator, the value seems to have been sent correctly. Does anyone know why? All help is greatly appreciated. The controller I'm connected to is a WATLOW F4.

---MODBUS Packet details---
Slave address: 1
Read Write: 6
Start Address 1: 01
Start Address 2: 2c
Value 1: ff
Value 2: 9b
CRC 1: 73
CRC 2: 164

ASCII characters sent: !,ÿI¤!
Buff data: !,I¤!

[download]
                $data = join('',@buffor);                           #M
+odbus frame to scalar
        #       chomp($data);
                print "ASCII characters sent: !$data!\n";
                if ($Telnet) {
                        $pass=$ob->print($data)
                        or warn "Modbus client : problem with send: $!
+\n";
                } else {
                        $pass=$ob->write($data)
                        or warn "Modbus client : problem with send: $!
+\n";
                }

                if ($Telnet) {
                        # Telnet
                        $TimeOut = int($TimeOut / 1000);         # Con
+vert to seconds
                        $ob->errmode('return');
                        my $i = 0;
                        do {
                                $Buffer = $ob->get(TimeOut => 1);
                                print "Buff data: !$Buffer!\n";
                                if (defined($Buffer)) {
                                        $i = 0;
                                        $Reply .= $Buffer;
                                } else {
                                        $i++;
                                }
                        } until ((! defined($Buffer) and $i >= $TimeOu
+t) or length($Reply) >= 8);

[download]

In reply to Telnet.pm and Negative Values for Modbus by PaulNg

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