As mentioned the real answer is no unfortunately. I used to use raw printer bits for all kinds of stuff. Not anymore. Regards Paul WB8TSL
On Fri, Jan 11, 2013 at 10:43 AM, Jim Lux <jim...@earthlink.net> wrote: > On 1/11/13 7:00 AM, Nathaniel Bezanson wrote: > >> J. L. Trantham wrote: >> >>> Is there a way to connect a parallel port to a computer via USB? >>> Not a device that shows up as 'USB Print Support' but, instead, >>> shows up in Device Manager as an LPT port? I have been able to do >>> it via PCMCIA to Parallel Port adapters but I have never found a >>> USB device that would do this. >>> >> >> Nope. Look at how the original PC LPT port works -- it's basically a >> buffer chip or two, connected to some address decoders, sitting at a >> particular spot (0x378) on the CPU's I/O bus. There's simply no way >> to abstract that -- it'd be like asking for USB RAM or a USB BIOS >> chip. >> > > Actually, though, with modern fast computers, it *is* possible to abstract > it (although tricky and difficult), because the printer port is SLOW. > You set up that memory area as protected, so an access causes a trap. The > kernel fields the trap and does the needed stuff to control your fancy LPT > port emulator hardware via USB or Ethernet and send/receive the bits. > > After all, that printer port was designed/specified to talk to devices at > no more often than 1 microsecond (that is, you could change the state of > the Strobe line), and practically speaking, with that 4.77MHz ball o'fire, > the strobe pulse was typically a bit longer. > > All those LapLink type cables that did high speed transfers between > computers using parallel printer ports back to back ran at transfer rates > around 200 kilotransfers/second, sending 4 bits at a crack each way, and > that's about as fast as you could bit bang. > > > Ugly? sure > Pain in the rear to implement in software? yep > Requires a very special hardware interface? Almost certainly. > > > > > > >> Software written to bitbang the port will have to be rewritten to use >> some other form of I/O. For the typical cases of bitbang interfacing, >> the FT245R is a very capable little chip, and can be dropped in place >> of the parallel port, to talk to legacy hardware. It just needs new >> software to take those raw IN and OUT instructions and fire them over >> an abstraction layer, which will pass them through the USB stack and >> out to the device. >> > > That is, trap the I/O instructions in userspace and use a kernel driver to > emulate it. > > > >> There is an exception -- If you're running legacy software under a >> modern OS that prevents raw hardware I/O anyway, it's possible to >> hook those IN and OUT instructions, and write a generic driver that >> passes the traffic over USB. It's slow, unstable, and basically a >> miracle if it works. But it's worth a try: >> http://www-user.tu-chemnitz.**de/~heha/bastelecke/Rund%20um%** >> 20den%20PC/USB2LPT/index.html.**en<http://www-user.tu-chemnitz.de/~heha/bastelecke/Rund%20um%20den%20PC/USB2LPT/index.html.en> >> >> > Exactly.. > > > > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.