USB to parallel adapters... How do they work?

  • Thread starter Thread starter WipeOut
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WipeOut

Hi,

I have searched around and can't seem to find the answer to this..

I have a PC that only has one parallel port and already has a printer
attached to it.. I now have to add a till slip printer to the same PC
that is also parallel..

PCI parallel port add on cards are pretty hard to come by and I cant
really wait because its quite urgent that it gets done..

So my other option is to use a USB to parallel adapter.. My concern is
that I don't know how this works..

For example on a Windows XP PC will the adapter emulate an LPT2 port so
the driver software has no idea that the printer is not connected
directly to a parallel port??

If anyone can shed some light on how these adapters actually work and if
there are any know issues with them that I need to look out for I would
appreciate it..

Thanks
 
If anyone can shed some light on how these adapters actually .
work and if
there are any know issues with them that I need to look out for > I would appreciate it..
Click to expand...

I don't have all the details as I never had to make anything in USB
before, anything that I would make would be well serial.

Basicly usb is a serial bus. I.e. 1s and 0s cross a line, another line
back, +5v for power, and signal ground. The main differences over old
serial are the speeds it can communicate with, and the virtual ports.
For example you jack in a printer, it's identified as usb001 for
example... the software sends data to the virtual port which is labled
"this is for you mr. usb001".

Parallel rather than being 1s and 0s cross a line is a series of 8
lines each one with 1s and 0s. Well in 8bit parallel that is, 16bit
parallel would be simply more lines. Basicly in many ways it's like
having 8 serial ports to one device, 8 times the data is transmited at
a given time. There are also other lines too, i'm busy, i'm out of
paper, that sort of thing. Basicly somewhere around +.8v is low IIRC
and 5V=high. low=0 high =1.

Basicly, off the top of my head and not researching the issue, and not
ever actually having to have used a usb to parelell controler, I would
assume that data is sent to the virtual port usb001 for example. This
data transmited in serial form is then buffered and then trasmited once
8 bits are received then transfered to the printer.

Virtual port: Hey usb1 "0-1-0-1-0-1-0-1 0-1-0-0-1-0-0-1"
Adpater: ok, printer do this
Adpater: "01010101"
Adapter" "01001001"
Printer "HI"

This is a very simplified example and would only work on printers that
still print standard ascii, and without an "end of line" or "eject
page" command it would probally sit there looking stupid. Parallel
simply put has no provisions for sharing devices, there is no hey
you... anything transmited from the pc to that port is done so without
regards to what is out there, but so long as you have the right driver
it doesn't matter.

While 8times the data is sent at a given time, it's not really faster
than USB, though ecp was faster than the old usb spect... the high
speed usb is far faster than parallel ever was.

The big issue i'm aware of is USB was never really supported under dos,
so it wouldn't be LPT2: unless you redirected the ouput from lpt2: to
usb001: for example. Network is supported if you have the software...
dos for workgroups from microsoft for example, it's a free download.
You can net use a network printer as lpt2: for example, and define any
printer you want that's on a machine that is shared including your own
(127.0.0.1). This is one workaround if you have a USB printer and need
dos support and nothing else works.
 
The drivers that come with the USB to LPT adapters emulate an LPT
port... Windows sends data to LPTx: and the driver translates that to
USBx. the whole process is invisible and unless it's an old, clunky
DOS program you will have no problems.
 
I have a PC that only has one parallel port and already has a printer
attached to it.. I now have to add a till slip printer to the same PC
that is also parallel..

PCI parallel port add on cards are pretty hard to come by and I cant
really wait because its quite urgent that it gets done..

So my other option is to use a USB to parallel adapter.. My concern is
that I don't know how this works..
Click to expand...

Another different method is to add a Data Switch box
like the Belkin F1B024-E. This connects one (standard)
parallel printer input and two printer outputs, with a switch
on the front that controls which output is in use. Price
about $20. Its usefulness to you probably depends on
how often you need to change the switch setting.
 
WipeOut said:
Hi,

I have searched around and can't seem to find the answer to this..

I have a PC that only has one parallel port and already has a printer
attached to it.. I now have to add a till slip printer to the same PC
that is also parallel..

PCI parallel port add on cards are pretty hard to come by and I cant
really wait because its quite urgent that it gets done..

So my other option is to use a USB to parallel adapter.. My concern is
that I don't know how this works..

For example on a Windows XP PC will the adapter emulate an LPT2 port so
the driver software has no idea that the printer is not connected
directly to a parallel port??

If anyone can shed some light on how these adapters actually work and if
there are any know issues with them that I need to look out for I would
appreciate it..

Thanks
Click to expand...

Thanks for all the replies.. I will give it a try and see how it goes..
sounds like it should work fine..
 
Hi,
So my other option is to use a USB to parallel adapter.. My concern is
that I don't know how this works..
Click to expand...

TMK, it doesn't entirely emulate an LPT port, but creates a Printer Class
port, which works like a paralell port to the printer driver, but not as an
LPT port at a lower level, meaning that only a Windows printer driver can
use that port.
 
If you have a network, you can use a network print server. You might
have to hit Ebay to find one with a parallel interface - most of the
computer store models are USB.
 
My problem is the reverse of yours and I am curious whether a
USB-Parallel adapter would work.

I have a USB printer that I want to work with a DOS program Symantec's
Q&A 4.0

The program can work in Windows XP, but is not able to see USB
printers. I had tried the NET USE command line, but that did not work.


My last resort was to create shortcuts that converted the Q&A File and
Q&A Word print output to a Text file, which I can then print from
Windows Wordpad.

If I connect the USB printer to an adapter and then connect the adapter
to the parallel port, would the LPT1 port work?
Click to expand...

Probably not since Q&A is a DOS app designed
to work with DOS printer drivers and Q&A was off
the market before non-DOS (Windows) printers
became available.
 
cbislander said:
If I connect the USB printer to an adapter and then connect the adapter
to the parallel port, would the LPT1 port work?
Click to expand...

Highly unlikely as the USB port on the adaptor isn't a USB
controller/master.
 
If I connect the USB printer to an adapter and then connect the adapter
to the parallel port, would the LPT1 port work
Click to expand...

No. Like many smart logic adapters, they aren't reversable.

The pinciple of the adapters is they create a printer class USB device, and
direclty interface to the printer.
 
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