Capturing Parallel Port Data

[Bernd Walter]

On Sat, Dec 16, 2006 at 11:12:44AM +1030, Daniel O'Connor wrote:
> On Saturday 16 December 2006 10:24, Mr CW wrote:
> > Thank you for the pointers.  It sounds like reading data back from the
> > parallel port is not a common thing to do, although I thought parallel port
> > projects might have done this.  Then I realized that most PIC programmers,
> > parallel port displays, etc. usually only receive data, not send it back to
> > the computer...
> 
> It is pretty easy to read data in a GPIO kind of fashion - you can set the 
> data direction (PCD) to input and then use PPIGDATA. However for what you 
> want the each byte of the data stream is marked by a STROBE pulse and AFAIK 
> there isn't a preexisting way to handle this.

Well - the hardware is made to write and in some fashion to read data
from a printer, not to simulate one.
Using it for a self defined protocol is something else.

> > I'm still looking into this, so any other suggestions are very welcome.
> 
> If it was me I'd use a microcontroller (eg AVR) to turn the parallel data into 
> a serial stream and read it in to a PC's serial port. However we already make 
> PCBs and write microcontroller code at work..
> 
> Actually maybe something like this would do what you want 
> http://www.bb-elec.com/product.asp?SKU=232SPS2
> 
> I think then you could just plug it into the FreeBSD box and log the stuff 
> coming from the serial port.

I did something like this on a C64 to scan lpt data from a PC and
pass it to a serial (IEC-Bus) commodore printer.
Well, it's been a very long time since then, but I asume something like
the FT245BM (http://www.ftdichip.com) should do.
The FT245BM is a generic parallel to USB device Interface.
It's handshake features on the parallel side should match the
requirements to simulate a printer - maybe with some 74ls.
The other side is USB device and supported by our uftdi driver.
The driver handles it as an virtual RS232 port.

-- 
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