Re: [PARPORT] PLIP and ECP/EPP ports
Fri, 25 Sep 98 09:19:33 +0200


> ...
> these ports' handshaking and I'm having trouble trying to design a
> parallel cable that could do the job (establish a bidirectional data
> channel) under either mode (it doesn't seem quite feasible without extra
> circuitry, something I was trying to avoid).
I don't know very much about the PLIP protokol. But I have to computers I
also would like to connect via PLIP.

More: As I posted some days ago, the generic IEEE1284 support for
parport will work soon. It is designed for any driver using an
maybe IEEE1284 compliant device. This IEEE1284 support will autoprobe
a device for available IEEE1284 modes, if activated, and will mask it with
the abilties of the computer's parport. Then, it provides functions like
parport_ieee1284_read_block and parport_ieee1284_write_block.
Those function will negotiate with a peripheral the "hightest" available
(can be overwritten by software) IEEE1284 mode and then send or receive

Some days ago, I posted, that probably my code will be available this week,
but there are still some bugs and my actual kernel is still 2.1.109. Therefore
I will need the week end for bug fixing and on Monday I will look for the
most recent kernel, to patch the most recent parport code with that
generic IEEE1284 support.

Of course, not all IEEE1284 modes will be implemented in my first release
of the IEEE1284 support, but it will w o r k and the remaining modes
will follow.

Now to your actual problem, the PLIP driver and an appropriate parallel cable:
I assume you want on both computers a "host parallel port", not a
"peripheral parallel port" and you know, that the i/o-directions are
just switched on each port - except of the data pins for a bidirectional
port, which is used by ECP and EPP. In the ECP (or EPP) handshake we
find pairs of respective handshake signals, one of each data flow directions.
Consequently the cable design should provide "crossed wires" according
to those signal pairs. Do you have specs about ECP ... or should I send to you
a "map" of the preferable wiring of such a PLIP-ECP cable?

Now to the software: ECP is a master-slave-protocal (host-peripheral).
But I think I shouldn't be too difficult to modify the IEEE1284 code,
I'm actual writing, to manage a ECP peer "as peripheral" - let me think
about it during the week end! If so, you could concentrate on the PLIP
protocol part and use the functions soon provided by parport_ieee1284.c.


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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:23 EST