USB to Parallel adapter?

[Roger Hamlett]

I would think that one of you bit-bangers could design a USB-to-LPT
device and then write software to take parallel port commands and
convert them to USB (and back). No?

The problem is that devices like this, do not take 'parallel port
commands', but direct bit I/O, often at high rates. So (for instance), the
driver may issue something like a 1uSec pulse easily when talking directly
to the port, but via the 'time sliced' system used on USB, this becomes
very difficult indeed. The only 'universal' way to do it for output, would
be to use something like a bulk I/O device, and sample the data to be sent
perhaps every uSec, and then send this as a block to the USB device, which
generates the output at the same rate. This however would fail, if the
communication is bidirectional. If (for instance), the local driver
expects to output a bit, and then only a uSec latter, retrieve a 'reply'.
By the time the transmission is packetted up, and sent over USB, then the
reply is received, hundreds of times the expected delay wuld have taken
place. The way it can be done, is to put significant intelligence in the
USB device, and program this to output the required patterns, and retrieve
the data, then send this as a 'non timing critical' transaction over USB.
This can be done, and several companies do such adapters for their older
devices, but it requires a new local driver, and custom code in the USB
device, which makes this a more expensive solution....

Best Wishes

 

[Joerg]

Hello Jim,

So bit-bangers aren't up to analog-level design ?

Bit bangers do not believe there is an analog world. On account of Max
Planck, they say.

 

[Rich Grise]

As a PC 'scope in my shed/workshop I use the 'ADC-200/50' from Pico
Technology.
http://www.picotech.com/high-speed-oscilloscopes.html
It's one of their older products and so has a parallel port connector,
not USB like the new stuff.

The ancient W98 PC in the shed is very unreliable I'm replacing it
with a mid-range laptop. But of course that won't have a parallel
socket.

What makes you assume that?

The first three here have parallel ports:
<http://shop4.outpost.com/search?sea...string=motherboard&cat=&submit.x=0&submit.y=0>
I stuck angle brackets in hopes the link won't wrap.

I know, you don't have Fry's in Britain, but you must have _something_
like it! The motherboards all come from China anyway, after all.

I think probably a whole lot of motherboards still have the
parallel port, it's just that not all desktops load the connector.

A new PS wouldn't hurt either, and a decent operating system. ;-)

Good Luck!
Rich

 

[Rich Grise]

So bit-bangers aren't up to analog-level design ?

Ha, ha. It's not the connecting of the dots - it's trying to do _anything
at all_ synchronously on a Windoze OS.

Good Luck!
Rich

 

[Paul E. Schoen]

Ha, ha. It's not the connecting of the dots - it's trying to do _anything
at all_ synchronously on a Windoze OS.

Good Luck!
Rich

Apparently there is a low-level microsecond timer that can be accessed. See
http://www.codeproject.com/cpp/precision_timer.asp for some information.

Here is software that claims 1 millisecond asynchronous event scheduling:
http://www.ryledesign.com/winhrt.html

Here is another good reference page:
http://www.geisswerks.com/ryan/FAQS/timing.html

However, it is probably best to say goodbye to the fading parallel port. In
my case it may be a problem because I have some very expensive software
that is protected by a dongle, and reverts to DEMO mode if it is removed
(Save functions are disabled). I was worried about this in case I lost the
dongle or it stopped working, or having to pay a huge price for a USB
dongle. However, I found the ultimate solution. The VB script has a "Save"
function that is not disabled, so I don't really need the dongle after all!
Hooray for back doors!

Paul

 

[Nico Coesel]

I would think that one of you bit-bangers could design a USB-to-LPT
device and then write software to take parallel port commands and
convert them to USB (and back). No?

USB doesn't like bitbanging because USB relies on polling. It is
probably much easier to create something that works over ethernet.

 

[Malcolm Reeves]

USB doesn't like bitbanging because USB relies on polling. It is
probably much easier to create something that works over ethernet.

At the risk of repeating myself since no one seems to have commented
on my post, the practical solution is to get a PCIMIA card such as
from http://www.transdigital.net/ . I have one and it works with my
Velleman scope and Xilinx parallel cable.

There is no practical general purpose USB solution for all the reasons
mentioned here. Cost wise the PCIMIA solution is similar to Pico USB
adaptor but of course the PCIMIA solution works with all units needing
LPT.

 

[Tim Baldwin]

At the risk of repeating myself since no one seems to have commented
on my post, the practical solution is to get a PCIMIA card such as
from http://www.transdigital.net/ . I have one and it works with my
Velleman scope and Xilinx parallel cable.

There is no practical general purpose USB solution for all the reasons
mentioned here. Cost wise the PCIMIA solution is similar to Pico USB
adaptor but of course the PCIMIA solution works with all units needing
LPT.

 

[Charlie Edmondson]

At the risk of repeating myself since no one seems to have commented
on my post, the practical solution is to get a PCIMIA card such as
from http://www.transdigital.net/ . I have one and it works with my
Velleman scope and Xilinx parallel cable.

There is no practical general purpose USB solution for all the reasons
mentioned here. Cost wise the PCIMIA solution is similar to Pico USB
adaptor but of course the PCIMIA solution works with all units needing
LPT.

Also, for those on laptops, many laptop manufacturers take a few
'shortcuts' on their parallel port implementations. I don't know how
many times I got a call from some engineer "I just got a new laptop, but
the dongle doesn't work on it!" This was especially true for docking
stations. It seems like they didn't implement all the pins directly,
but multiplex them internally somehow...

Charlie