frisk@rhi.hi.is (Fridrik Skulason) (01/11/89)
I need to connect a set of eight switches to my PC. The most simple way
to do it seems to be connecting them to the parallel port, and using it
as input port instead of output.
My question is: Does anyone have a code fragment (in C, assembler or
whatever) for changing the port into an input port?
Thanks....
--
Fridrik Skulason University of Iceland
UUCP frisk@rhi.uucp BIX frisk
This line intentionally left blank ...................pfales@ttrde.UUCP (Peter Fales) (01/11/89)
In article <704@krafla.rhi.hi.is>, frisk@rhi.hi.is (Fridrik Skulason) writes: > I need to connect a set of eight switches to my PC. The most simple way > to do it seems to be connecting them to the parallel port, and using it > as input port instead of output. > > My question is: Does anyone have a code fragment (in C, assembler or > whatever) for changing the port into an input port? Sorry, the standard PC parallel port hardware is not capable of being used as an input port no matter how clever your code is. There was an article a few months ago in Steve Ciarcia's "Circuit Cellar INK" magazine on a simple hardware modification to correct this problem. It requires cutting a trace, adding a wire, and is pretty simple if you are good at tracing out paths on a circuit board. -- Peter Fales AT&T, Room 2F-217 200 Park Plaza UUCP: ...att!ttrde!pfales Naperville, IL 60566 Domain: pfales@ttrde.att.com work: (312) 416-5357
network@hgcvax.uucp (craig chaiken) (01/13/89)
In article <704@krafla.rhi.hi.is>, frisk@rhi.hi.is (Fridrik Skulason) writes: > I need to connect a set of eight switches to my PC. The most simple way > to do it seems to be connecting them to the parallel port, and using it > as input port instead of output. > > My question is: Does anyone have a code fragment (in C, assembler or > whatever) for changing the port into an input port? > (*** The following is an except of my, soon to be published book, ***) (*** _Blueprint of a Local Area Network_. It soon be available from ***) (*** M & T Publishing for $24.95 sometime around July. The book ***) (*** provides the source code and details the hardware necessary to ***) (*** build an inexpensive, customized IBM PC Local Area network. ***) (*** Both hardware hackers an assembly language programmers, alike ***) (*** will find that it is chock full of useful information, and ***) (*** techniques. ***) The parallel port on the IBM PC was designed for use with a parallel printer. It provides 8 output-only lines, mapped to bits 0 through 7 of I/O port 0378H, which are data bit 0 through data bit 7. It provides 5 input-only lines. mapped to bits 3 through 7 of I/O port 0379H, which are ERROR, SELECT, PAPER_END, ACKNOWLEDGE, and BUSY. And it provides 4 input/output lines, mapped to bits 0 through 3 of I/O port 037AH, which are STROBE, AUTO_LINE_FEED, INITIALIZE, and SELECT_IN (* Note - in order to input from this port, you must first send 04H to I/O port 037AH *). BUSY, AUTO_LINE_FEED, and STROBE input signals are inverted by the hardware, and must be negated in software. (*** End of Excerpt from Blueprint of a Local Area Network ***) Craig Chaiken Hartford Graduate Center Computing Services
warren@psu-cs.UUCP (Warren Harrison) (01/14/89)
> In article <704@krafla.rhi.hi.is>, frisk@rhi.hi.is (Fridrik Skulason) writes: > > I need to connect a set of eight switches to my PC. The most simple way > > to do it seems to be connecting them to the parallel port, and using it > > as input port instead of output. > > > > My question is: Does anyone have a code fragment (in C, assembler or > > whatever) for changing the port into an input port? > > Sorry, the standard PC parallel port hardware is not capable of being > used as an input port no matter how clever your code is. > > There was an article a few months ago in Steve Ciarcia's "Circuit Cellar > INK" magazine on a simple hardware modification to correct this > problem. It requires cutting a trace, adding a wire, and is pretty > simple if you are good at tracing out paths on a circuit board. > > -- > Peter Fales AT&T, Room 2F-217 > 200 Park Plaza > UUCP: ...att!ttrde!pfales Naperville, IL 60566 > Domain: pfales@ttrde.att.com work: (312) 416-5357 It would seem this is the case, and I would believe it, except many of the laptop to desktop data transfer utilities use the parallel port to transfer data (ie, one parallel port sends it and one receives it). For example, my copy of "The Interchange" (SMT, Inc.) includes a cable which you connect to the parallel ports of the laptop and the desktop to transfer files (in the event you don't have a 3.5" disk on the desktop). This results in *VERY* fast data transfer (obviously faster than is possible with a serial line). The product specs do not mention anything about hardware modifications, and it seems to work OK on my Amstrad laptop and my 286 clone (which are about as plain vanilla as you can get). This leads me to believe that in fact you can use the parallel port as an I/O device (albeit, the cable can't be more than 10' long) if you know what you're doing and are willing to write the appropriate software. Warren -- ------------------------------------------------------------------------------- Warren Harrison CSNET: warren@pdx.edu Department of Computer Science UUCP: {ucbvax,decvax}!tektronix!psu-cs!warren Portland State University Internet: warren%pdx.edu@relay.cs.net Portland, OR 97207-0751
ralf@b.gp.cs.cmu.edu (Ralf Brown) (01/14/89)
In article <1502@psu-cs.UUCP> warren@psu-cs.UUCP (Warren Harrison) writes: }It would seem this is the case, and I would believe it, except many }of the laptop to desktop data transfer utilities use the parallel port }to transfer data (ie, one parallel port sends it and one receives it). ... }The product specs do not mention anything about hardware modifications, These products probably use the five status lines which are usable as inputs. I'm sure that the cables are specially wired to connect the data lines from one port with the status lines of the other. -- {harvard,uunet,ucbvax}!b.gp.cs.cmu.edu!ralf -=-=- AT&T: (412)268-3053 (school) ARPA: RALF@B.GP.CS.CMU.EDU |"Tolerance means excusing the mistakes others make. FIDO: Ralf Brown at 129/31 | Tact means not noticing them." --Arthur Schnitzler BITnet: RALF%B.GP.CS.CMU.EDU@CMUCCVMA -=-=- DISCLAIMER? I claimed something? --
nather@ut-emx.UUCP (Ed Nather) (01/15/89)
In article <816@ttrde.UUCP>, pfales@ttrde.UUCP (Peter Fales) writes: > In article <704@krafla.rhi.hi.is>, frisk@rhi.hi.is (Fridrik Skulason) writes: > > I need to connect a set of eight switches to my PC. The most simple way > > to do it seems to be connecting them to the parallel port, and using it > > as input port instead of output. > > > > Sorry, the standard PC parallel port hardware is not capable of being > used as an input port no matter how clever your code is. > I'm glad I didn't know this when I wrote my "portfinder" routine, which finds the port name of the printer port -- you have to put a dummy plug in, which the program looks for. It does this by sending out 4-bit codes, then reading the various possible ports to see if it can find the code -- by using lines in the output port as input bits. As I recall (it's been several years) I could only input 4 bit codes, not 8 bit -- there weren't enough input lines for 8 of them. I did the input in two-nibble bytes. "`Impossible' is a challenge, not a truth." -- Ed Nather Astronomy Dept, U of Texas @ Austin
akm@uoregon.uoregon.edu (Anant Kartik Mithal) (01/15/89)
It certainly is possible to use the printer port for input. Lanlink is a software based network that uses printer ports to obtain up to .5 Mbit/S data transfer. If I remember correctly, the hardware for the printer port is set up as an I/O port, and there is nothing to stop anyone from inputting data on the ports.
cas@hoptoad.uucp (Curtis Spangler) (01/15/89)
> In article <704@krafla.rhi.hi.is>, frisk@rhi.hi.is (Fridrik Skulason) writes: >> In article <816@ttrde.UUCP>, pfales@ttrde.UUCP (Peter Fales) writes: > [ text elided ] > My question is: Does anyone have a code fragment (in C, assembler or > whatever) for changing the port into an input port? >> Sorry, the standard PC parallel port hardware is not capable of being >> used as an input port no matter how clever your code is. >> [ text elided ] Reference: The C Users Journal, Dec./Jan. 1989, Volume 7, Number 1 Address: 2120 W. 25th Street Suite B, Lawrence, KS 66046-9972 Telephone: (913) 841-1631 Article: High Speed, Real Time Data Acquisition In C By: J.F. Vibert & B. Cointot, page 39 Quoted without permission from page 48 of the above article: " Unfortunately, it appears from the available manuals that the printer parallel interface is limited to solely output data. When we checked the ROM BIOS listing in the IBM PC/XT Technical Reference Manual we found that the PPI chip which controls this port "can be read as well as written." This led us to think that it was possible to use it as input, too. This proved to be true when we tested it (see Listing 8). " "Listing 8" is a fragment in C titled sic "Function to demonstrate acquisition with the parallele printer interface." -- Curtis Spangler {sun,pacbell,uunet,pyramid,amdahl}!hoptoad!cas cas@toad.com
hundt@paul.rutgers.edu (Thomas M. Hundt) (01/16/89)
>many of the laptop ... transfer utilities use the parallel port to >transfer data Well, perhaps they are using the status lines, eg. "paper out", and shoving it through at high speed this way. So probably you can hook up maybe 3 switches and be able to read their input. I suspect the transfer programs are using two lines, one for clock and one for data, which would be sufficient. -- RRRRRR Thomas M. Hundt (aka hundt@occlusal.rutgers.edu) RR RR Gradual Student --- Electrical & Computer Engineering RR RR Rutgers University 201/932-5843(Lab) RRRRR 272 Hamilton St. #96 201/247-6723(H) RR RR New Brunswick, NJ 08901 RRR RRR Famous last words: "The virus ate it."
matthieu@laas.laas.fr (Matthieu Herrb) (01/16/89)
I've seen many authors saying that it is impossible to use // port as input. I don't have my technical reference manual here at work, but all they say is that this is not recommended. I wrote a few years ago a program to grab byte from a silly voltmeter, it uses 8 bit input and the // card used is still alive. -- \ / | Matthieu Herrb LAAS - RIA |\/|--| matthieu@idefix.laas.fr 7, avenue du Colonel Roche | | | 31077 Toulouse Cedex - France
pete@octopus.UUCP (Pete Holzmann) (01/21/89)
A couple of years ago I was interested in doing high-speed data transfer
between PC's. I checked the schematics and sure enough, as someone else
mentioned, there are 8 data out lines (normal data to printer), 5 input
status lines, and 4 lines normally for control output, but you can make
them input lines (sometimes by flipping a bit, but more reliably in my
experience by making the output float. Send a zero, I think, and you
can read whatever is out there...).
I had a set of test software running, and could do 70+KB/sec between two
PC's... never got around to turning it into a product. I wonder if it was
patentable?
Anyway, I'll probably never get around to doing anything useful with it.
As soon as I can rummage a little, I'll post some code to the net. Maybe
somebody can have some fun with it...
Pete
--
OOO __| ___ Peter Holzmann, Octopus Enterprises
OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014
OOOOO \___/ UUCP: {hpda,pyramid}!octopus!pete
___| \_____ Phone: 408/996-7746james@bigtex.cactus.org (James Van Artsdalen) (01/22/89)
In <485@octopus.UUCP>, pete@octopus.UUCP (Pete Holzmann) wrote: > A couple of years ago I was interested in doing high-speed data transfer > between PC's. [...] > I had a set of test software running, and could do 70+KB/sec between two > PC's... never got around to turning it into a product. I wonder if it was > patentable? Well, not any more. You have to file those patent papers within a year. In any case, there is an excellent commercial product called FastWire that does just this (it can also use one or more serial ports for transfers). It is so fast that we use it to make backups of entire hard disks at a time: a 30meg partition goes in a few minutes. -- James R. Van Artsdalen james@bigtex.cactus.org "Live Free or Die" DCC Corporation 9505 Arboretum Blvd Austin TX 78759 512-338-8789
chris@zorin.UUCP (Christopher Nielsen) (01/22/89)
In article <274@laas.laas.fr>, matthieu@laas.laas.fr (Matthieu Herrb) writes: > > I've seen many authors saying that it is impossible to > use // port as input. I have an article in front of me: "A programmer's guide to the parallel port" by Bruce Eckel, that appeared in "Turbo Technix". It describes using it in real world applications. It's short (6 pages) but describes (with listings) of how to programm the PC parallel port for input & output. He also mentions that the listings are available on compuserve as parallel.arc. Contact information... Bruce Eckel Eisys 1009 N 36th Street Seattle WA 98103 Christopher A. Nielsen ////////////////// Zorin Data Systems, Inc //// P.O. Box 5669 Santa Monica, CA 90405-0669 //// (213) 399-3804 //// UUCP: hplabs!sdcrdcf!zorin!info //// <<<<<<<<<<<<<<<<<<<<<<<<<< Zorin... "The Future OnLine" >>>>>>>>>>>>>>>>>>>>> < Online Product Information and other services - Call or write for free demo >
oferf@shum.huji.AC.IL (ofer faigon) (01/26/89)
There waere several queries recently about reading input through
the parallel printer port, but I don't recall seeing any definitive
reply.
The following is quoted from Steve Ciarcia's Circuit Cellar that
appeared in BYTE, vol 13, No.9 (September 1988), page 305:
Unfortunately, an irritating problem with the design of the PC
is that its standard parallel printer port is output only.
All the hardware needed to read or write 8 bits of data is
already in place, but it lacks a connection to enable that
function. While you can buy a custom parallel I/O board, I think
changing a single trace on the existing board might be worth it
to some readers. Figure 5 shows the single cut and addition to
convert a standard paraller printer port to bidirectional operation.
Of course, all the clone boards (even the IBM boards) seem to use
different IC numbers and assign the bits to different pins on the
ICs, so this modification can be a real mystery. If you are unwilling
to chop up your printer port card, buy a $50 clone printer port card.
They are usually bidirectional. Some clone boards also omit the input
connection between the data bus and pin 14 of the LS174.
...[some text deleted]...
...(a modified port will stil work correctly with all your other
software, simply because the code doesn't know about the change
and won't take advantage of it).
Figure 5 appears on page 310, and is a bit hard to reproduce here.
What it shows is the three chips involved (74LS374, 74LS244 and 74LS174),
and the one (or two) modifications needed:
- Disconnecting the output-enable pin (1) of the 374 from ground,
and connecting it to the unused output pin on the 174 (the figure
shows a connection to pin 15 - Q6, assuming Q1-Q5 are in use).
- If the connection between BDATA5 ant the input side of the 174
is missing, then connect them (the figure shown connection to
pin 14 - 6D, assuming 1D-5D are connected to BDATA0-4).
And a final quotation: "Actual pin numbers on your board will vary;
Trace the wiring from the DB25 connector to identify the right traces
and pins".
Have fun.
- Ofer Faigon TEL: +972-2-669-834
MAIL: P.O.B 7347, Jerusalem 91072, ISRAEL
BITNET: oferf@HUJINIX CSNET & INTERNET: oferf@shum.huji.ac.il