[PARPORT] custom cabling

From: Nate Jenkins (nate@uniwest.com)
Date: Thu Apr 17 2003 - 14:14:44 EDT

  • Next message: Blaise Gassend: "Re: [PARPORT] custom cabling"

    Hi,

    I have been using the parport module(s)* to communicate between two PCs for
    about 6 months or so now. However, it is too slow. The reason it is slow
    is because of at least two reasons....

    1. I am controlling the flow of data in software using a strobe/ack
    approach.
    2. I am using a standard LapLink style cable. This gives me access to send
    a nibble (4 bits), namely D0-D3.

    **Standard LapLink Style Cable Map**
    D7 -
    D6 -
    D5 -
    D4 - ~S7
    D3 - S6
    D2 - S5
    D1 - S4
    D0 - S3
      - S2
      - S1
      - S0

    So I am considering improving my speed by wiring a custom cable. I am
    thinking of this scenario to control the flow of data... The data Source PC
    will write to the data port, a full byte (8 bits, D7-D0). And then set its
    ~C0 to high to indicate the data is valid (like a strobe). Then the Dest PC
    would send back the same data on its data port so the Source PC could tell
    that the Dest PC had received the data. At that point it would drop the ~C0
    line to indicate to the Dest PC that the data is no longer valid. Then it
    would start all over again.

    The diagram is on both ends, so it would be the same for each PC. I wanted
    to see if my parallel port circuitry would be damaged if I wired it in the
    following way...

    **Proposed Custom Cable Map**
     D7 - ~S7 , (09-11) , [data7-busy]
     D6 - S6 , (08-10) , [data6-nAck]
     D5 - S5 , (07-12) , [data5-paper]
     D4 - S4 , (06-13) , [data4-select]
     D3 - S3 , (05-15) , [data3-error]
     D2 - ~C3 , (04-17) , [data2-nSelPrntr]
     D1 - C2 , (03-16) , [data1-nInit]
     D0 - ~C1 , (02-14) , [data0-nAutoLF]
    ~C0 - ~C0 , (01-01) , [nStrobe-nStrobe]

    Will this custom wiring make the magic smoke come out of the circuitry? Is
    this a bad idea? Do you have better suggestions for controlled 8 bit
    parallel port data transfer from PC to PC?

    * - parport module(s) referenced above that I am using in the program are:
    parport.o, parport_pc.o with /dev/ppdev using the 2.4.2-2 Linux kernel.

    Thank You,

    Nate

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