Connect LPT printer to serial port

You can download this for your platform and open the application and go to tools serial monitor. that will listen to the configured serial port. (You do not need an arduino for it to work.)

From their website:

Q: How do I use Hyperterminal to check communications?

A: Hyper Terminal is a Terminal program that is bundled with Windows.

To set up Hyper Terminal for use with an Ohaus balance, perform the following steps. The following assumptions are made for the purpose of explanation. 1. The computer uses Com1 2. The Balance Baud Rate is set to 2400 3. The Balance Data Bits are set to 7 4. The Balance Stop Bits are set to 2 5. The Balance Parity Bit is set to None 6. Handshaking in the balance is turned off

Open the program and enter a name for the connection. You will probably want to save the setup for future use. Press OK In the next screen click on the twirl down for the "Connect using" box and select the COM port your computer uses.

Click OK and the COMx properties box will be displayed. (Which COM port appears will depend on the setting in the previous step.)

Set the parameters to match the parameters in the balance. See the instruction manual for the balance. The usual defaults are 2400 baud, 7 data bits, no parity, 2 stop bits and no handshake. When finished press apply then press OK.

The terminal screen will be displayed.

Select CALL from the menu bar and select Disconnect. The "Connected" at the bottom left of the screen will change to "Disconnected".

Select FILE from the menu bar and select Properties.

Select the Settings tab.

Check Windows Keys and Del.

At the bottom of the box click on ASCII Setup.

Check the first two boxes and put 11 in the next 2.

Click Ok twice.

From the Call menu select Call.

"Call" will be displayed at the lower left of the terminal screen.

You are now ready to communicate with the balance. The best way to test the connection is to press print on the balance. Other commands are listed in the instruction manual for the balance.

And some additional info from that site:

How can I get my Defender 5000 indicator (T51P or T51XW) to print without inserting an extra line feed? I am using a label printer with preprinted labels and every other label is wasted. A: You can do this by going into the menu under Print1 or Print2 and setting the format to Single. Q: Ok now I am printing a single label but there is too much information. I am still using a T51P. A: Again go into the Print1 or Print 2 menu. You can turn off all the heading and GLP information you need too. You can also turn off the Gross, Net and Tare printing and just leave the result. You also have the option to print the result as a number only by setting it to NUM. This will eliminate the unit of measure. Q: I am using a 7000 series Defender indicator (T17P) and I can not clear the accumulator. I have followed the instructions in the manual but it does not clear. A: Press and hold the "info" button until the display shows "StatS". Then press the "CLR" button to clear the accumulator.

taken from: http://us.ohaus.com/us/en/home/support/faq.aspx#S16

Ok. So you connected a parallel device/printer via a "USB-to-Parallel IEEE-1284"-cable to the USB-port of your computer. Now you need to directly communicate to it. I understand you can't change the software directly to communicate with modern ports like USB001 etc. like the drivers of scanners do. And the software you have needs to communicate by normal protocol for old-LPTx ports (i.e. 0x378 instead of LPT1 etc.)

That leaves you with one option and that is "emulation". This should be done by the driver which came with the "USB-to-Parallel IEEE-1284"-cable. This driver should make a LPTx port and capture port-communication etc. But most (if not all) of these adapters come with drivers who emulate an USB-printer. In most cases this is the easiest (and even in case of old DOS-programs this can be solved with a NET command) but when it comes to real port-communication it is useless.

So you need to find a program that can emulate a LPTx (and its ports) and bidirectionally communicate with (any) USB-driver on your computer. I have not found one (yet).

The only thing useful i found was this Converter From USB To Parallel. This one emulates the LPTx and ports and communicates directly with the adapter. I have not tested this myself but the info-page looks promising. From the help-file:

The USB2LPT device and its driver enables redirecting of port access by random application software to a USB-attached parallel port, i.e. emulating a parallel port via USB. This unique solution works on all USB supporting Windows operating systems.

It does label its own driver as "Driver unstable" but you'll get the idea for what you're looking for. It also needs a special USB2LPT-adapter though. From its faq-page:

Q3. Can I use the USB2LPT.SYS driver with a regular (cheap) USB to parallel printer adapter?
A. Of course not! It's never possible due to design limitations of such adapters. See below.

It also lists as a minus for itself its Reduced speed due to emulation (expect 10..100 times slower). But it will allow communication with Base address same as built-in (378h, 278h). If you like you can make your own adapter. The schematics are all on the site. Here you can find complete instructions (including videos) on how to build one. Or else you can mail him for details on how to get one.