Standard Parallel port read

Thanks again Damion,

I have some I/O on the SBC but they all are occupied, the modification for particular customer needs another 16 Inputs to read.

I am still not sure that one can not use all the Parallel port pins ?..

As Parallel port can be used in SPP , EPP , ECP Modes, you are absolutely right for EPP and ECP but in SPP story is different.

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ON this site he is reading from all the pins I cant read :) :(

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Pin No (D-Type 25) Pin No (Centronics) SPP Signal Direction In/out Register Hardware Inverted

1 1 nStrobe In/Out Control Yes 2 2 Data 0 Out Data 3 3 Data 1 Out Data 4 4 Data 2 Out Data 5 5 Data 3 Out Data 6 6 Data 4 Out Data 7 7 Data 5 Out Data 8 8 Data 6 Out Data 9 9 Data 7 Out Data 10 10 nAck In Status 11 11 Busy In Status Yes 12 12 Paper-Out / Paper-End In Status 13 13 Select In Status 14 14 nAuto-Linefeed In/Out Control Yes 15 32 nError / nFault In Status 16 31 nInitialize In/Out Control 17 36 nSelect-Printer / nSelect-In In/Out Control Yes 18 - 25 19-30 Ground Gnd Table 1. Pin Assignments of the D-Type 25 pin Parallel Port Connector.

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The only different : these 4 pins are Inverted????????????.

Also if I believe beyond logic than it says in SPP I can never able to read pins 2-9, which I am already reading??.

I am totally confused???.. Is any one out there wants to share any experience in this controversial issue ?.

Another solution can be to use the multiplexer and read the pins, but do I really need to use the hardware ???.???????????

Regards,

Rushi

I was thinking you only had 12 input pins, but it looks like you can read 17 pins(one extra thrown in as a bonus).

A useful reference is the IBM Technical Reference Personal Computer AT March 1984 (20 years ago!)

The above includes schematics of the AT serial/parallel board. I had to fathom the mysteries of the 74LS155 decode logic to get that 17th input pin for you. Tried scanning it in, but my scanner is dying, so no luck.

Keep in mind that a lot of these pins are normally outputs until switched to "input mode".

See below for some software.

Heres some code to help explain and test:

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Included is this fun little prog: To compile: gcc -O1 in17.c -o in17

#include

#define InB inb

#define OutB(_p, _d) outb(_d, _p)

#define LPT_BASE 0x378

#define LPT_DATA LPT_BASE+0

#define LPT_STAT LPT_BASE+1 int main(int argc, char *argv[])

{

unsigned char data,stat,ctrl,i;

printf("in17.c - test all 17 lpt inputs\n");

if (ioperm(LPT_BASE, 3, 1)) {

printf("Could not get IO permissions\n");

exit (1);

}

OutB(LPT_CTRL, 0x24); // set all output's high, so we can read em

printf("Connect wire from gnd(18-25) to each pin:\n");

printf("Input Pins: 2-9=data 10=ack 11=busy 12=PE 13=slct

15=error\n"); printf("AND Output Pins: 1=strobe 14=auto_fd 16=init 17=slct_in\n");

// Data:01234567 Stat:01234567 Ctrl:01234567

printf(" 8 6 4 2 11 17 \n");

printf(" 9 7 5 3 10 16\n");

printf(" 12 14\n");

printf(" 13 1\n");

printf(" 15\n");

while (1) {

data = InB(LPT_DATA);

stat = InB(LPT_STAT);

ctrl = InB(LPT_CTRL);

printf("Data:");

for (i=0; i> i) ? '1' : '0' );

}

printf(" Stat:");

for (i=0; i> i) ? '1' : '0' );

}

printf(" Ctrl:");

for (i=0; i> i) ? '1' : '0' );

}

printf("\x0d");

fflush(stdout);

usleep(100000L); // sleep .1 secs

}

ioperm(LPT_BASE, 3, 0); // release

return 0;

}

Karl.