Forums

USB to LPT converter for wiggler?

Started by ds19968902 October 15, 2006
On Tue, Oct 17, 2006 at 07:08:41PM +0200, Bertrik Sikken wrote:
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> ds19968902 wrote:
> > I would really like to see continued support by the IDE developers to
> > keep wiggler and have it grow to a standard. This is probably just
> > beating a dead horse since wiggler is really just software, and not
> > really a hardware interface. I just wish jtag across all devices could
> > really live up to its potential
> >
> > I am not in need of a solution, i have a parallel port =), i am more
> > just curious about the possiblity of doing something along these lines
>
> Indeed, I'm still a bit puzzled about how JTAG can be an industry-wide
> standard (IEEE even), but still there appears to be no generally used
> software API for JTAG devices (please correct me if I'm wrong).

http://openwince.sourceforge.net/jtag/
Supports many JTAG programmers, and targets.
Take care,
-Chris

--
| Christopher Cole, Cole Design and Development c...@coledd.com |
| Embedded Electronics and Software Design http://coledd.com |

An Engineer's Guide to the LPC2100 Series

> Indeed, I'm still a bit puzzled about how JTAG can be an industry-wide
> standard (IEEE even), but still there appears to be no generally used
> software API for JTAG devices (please correct me if I'm wrong).
>
> Instead, almost everything that uses JTAG comes with its own cable and
> its own specific JTAG driver.

Bertrik,

I, too, am a bit surprised at that, as well. But, if you reflect on it,
name me one IEEE standard that does have a good software specification
layered on it. I only see such specifications on 'standards which were
in use before they became IEEE standards' like firewire (ne IEEE1394).

IEEE is for EEs. Maybe EEs don't value software specifications? I
sure wish they would join the rest of the world and start providing
software APIs as part of their standards? Imagine how much simpler
life would be if IEEE 802.3 didn't have a different specification
for each different chipset?

Cheers,
David
alexz4lpc wrote: --- In l..., "ds19968902" wrote:
>
> Dominic, That makes a lot of sense.
>
> The appeal is that wiggler clones are well supported by more than just
> one IDE and can be made for pennies but comes at a cost of a parallel
> port which im not too fond of.
>
> I am really just curious if it would be possible to create a usb
> wiggler that could actually just utilize the same crossstudio or iar
> driver and possibly have a "psuedo" lpt driver that would actually
> translate the bit-banging instructions into chunks of data, but if you
> must wait for a response from the target after every toggle of a pin
> then this dosn't improve the speed.
>
> Something else that just popped into my head: What if the psuedo lpt
> driver actually just monitored the address writes and translated them
> into a serial stream which then went over usb and gave the command to
> a small microcontroller that then toggled the jtag pins accordingly
> and relayed the data back. Would something like this work, and if it
> did could it have the potential of being faster than the original
wiggler.
>
> I would really like to see continued support by the IDE developers to
> keep wiggler and have it grow to a standard. This is probably just
> beating a dead horse since wiggler is really just software, and not
> really a hardware interface. I just wish jtag across all devices could
> really live up to its potential
>
> I am not in need of a solution, i have a parallel port =), i am more
> just curious about the possiblity of doing something along these lines
>
> Thanks!
> eric
>
> --- In l..., Dominic Rath wrote:
> >
> > On Sunday 15 October 2006 11:57, ds19968902 wrote:
> > > I was wondering if anyone knew of solution to convert a usb port
to a
> > > parallel lpt port so that I could use a parallel wiggler with
> > > crossstudio without having a parallel port. It seems like such a
> > > simple idea but I can't find anything about it. Do any vendors like
> > > ftdi offer a chip to do it?
> > > Thanks, eric
> >
> > There are USB-to-LPT converters, but you can't use these to work
with a
> > Wiggler, as they are mostly for use with parallel port printers.
> While the
> > idea might seem simple, you can't just access a device via USB like
> you would
> > with a parallel port interface.
> > The Wiggler is a bitbanging interface, toggling parallel port data
> lines and
> > reading back signals on the status lines, and each access to the
> port takes
> > about 1us. On a USB interface, you send data in packets, in frames
> of 1ms
> > (USB 1.1) or 125us (USB 2.0) - bitbanging with that latency is going
> to be a
> > performance nightmare.
> > All Wiggler software I've seen so far expects the parallel port to be
> > accessible via I/O accesses (inb, outb) to some of the standard
> parallel port
> > addresses (0x278, 0x378, ...), but the USB-to-LPT converters don't
> offer this
> > access type.
> >
> > Regards,
> >
> > Dominic
>
Folks, you have to remember that USB parallel port adapters are not
parallel ports from Windows perspective of view - they do implement
printing services over USB bus, which is standartized by USB
consorcium. All the "wiggler" like devices operate via direct access
to the parallel port registers, which is prohibited in current Windows
revisions (from user space perspective of view). You have to have
kernel mode driver which will permit such an access. There are few
libraries around which do permit such an access (they do implement
kernel driver functionality inside), but even having such a driver,
but missing physical parallel port might be an issue. The thing is,
that parallel bus is enumerated entity upon boot-up - you should
remember bootable parallel port floppy devices, Jazz drives etc. In
order to fake the register access you will have to implement intercept
using debug-like trace/stop point with the corresponding handler - I
saw it working somewhere
(http://www-user.tu-chemnitz.de/~omat/bastelecke/Rund%20um%20den%20PC/USB2LPT/index.html.en)

Take a look - this is exactly what are you looking for. The main trick
is on a Windows side, not the micro.

Just my 10 cents.

Alex

Thanks & Regards...
Visakh.S
Embedded Design Engineer
Greyfusion Technologies Pvt Ltd,
Bangalore
Mob: +91 9900113264
v...@greyfusiontech.com
www.greyfusiontech.com

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