Re: can rPi drive PC-bidirectional Par-port?

From	Michael Black <et472@ncf.ca>
Newsgroups	comp.os.linux.hardware, comp.sys.raspberry-pi
Subject	Re: can rPi drive PC-bidirectional Par-port?
Date	2013-04-08 01:40 -0400
Organization	National Capital Freenet, Ottawa, Ontario, Canada
Message-ID	<alpine.LNX.2.02.1304080130510.7771@darkstar.example.org> (permalink)
References	<kjlvsl$o5l$1@dont-email.me> <kjt8eg$1gd$1@dont-email.me>

Cross-posted to 2 groups.

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On Mon, 8 Apr 2013, David wrote:

> At Fri, 05 Apr 2013 07:52:54 +0000, Avoid9Pdf rearranged some electrons to
> write:
>
>> Probably the PC parallel-port has TTL specs?
>>
>> So them 3.3V CMOS should drive it ?
>>
>> Can the 'bidirectionality' of the Par-port be tested/confirmed without
>> hardware tool, ie. by software?
>>
>> Since eg. IOMEGA par-port assumed at least a 4bit-wide bidirectionality,
>> perphaps all post-70's were bidirectional?
>>
>> == TIA.
>
> Raspberry Pi I/O is not 5V tolerant.
>
Ihadn't thought of that. So no handshaking.

I was thinking 3.3v into the parallel port (assuming it did allow input) 
was a bit iffy, it would depend on the circuitry of the printer port it's 
feeding.  It might work fine, or it might be noisy, not enough absolute 
difference between high and low.

But if the Pi doesn't want more than 3.3V, then nothing can come back to 
it until someone adds some buffers between the two to deal with the 
voltage variant.  At which point, they might as well add some buffers for 
the signal lines going to the other computer.

At which point, one might as well go RS-232 and just add line drivers and 
receivers.  One thing the clueless didn't specify earlier was that the Pi 
board apparently includes a serial I/O among those "general purpose I/O 
pins", so all that's lacking is the drivers and receivers.

Or, didn't the Commodore 64 just output TTL on the serial port?  I seem to 
recall endless articles about adding RS232 drivers and receivers so the 
computer would work with real RS232.  Get one of those, and you've got 
your 40character wide terminal, only it would be +5v ttl, not 3.3V.

Either somebody has to learn to solder, or the simpler solutions of the 
ethernet port, or the intended hooking the board up to a USB keyboard 
(easily found in the garbage, though not as common as PS/2 keyboards yet) 
and to a DVI or HDMI monitor or TV set.

Or, add a string of 8 toggle switches to input data into the Pi, and a 
string of 8 LEDs to indicate output from the Pi, and write a monitor to 
make use of them.  It wsa good enough in the days of the Altair 8800 
(though the front panel hardware was extensive) or the days of the Cosmac 
Elf (the RCA 1802 CPU was set up for jamming data onto the bus, so it was 
easy to have a front panel, and no monitor in ROM needed).  But it's a 
massive step down when the PI is so fancy that it can run full blown 
Linux, and is almost as good as the 1GHz/512meg computer I was using till
this past October.

    Michael

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Thread

can rPi drive PC-bidirectional Par-port? Avoid9Pdf@gmail.com - 2013-04-05 07:52 +0000
  Re: can rPi drive PC-bidirectional Par-port? Johann Klammer <klammerj@NOSPAM.a1.net> - 2013-04-05 12:12 +0200
  Re: can rPi drive PC-bidirectional Par-port? Anssi Saari <as@sci.fi> - 2013-04-05 16:39 +0300
    Re: can rPi drive PC-bidirectional Par-port? Unknown <dog@gmail.com> - 2013-04-07 17:50 +0000
      Re: can rPi drive PC-bidirectional Par-port? Rob <nomail@example.com> - 2013-04-07 18:19 +0000
        Re: can rPi drive PC-bidirectional Par-port? Michael Black <et472@ncf.ca> - 2013-04-08 01:43 -0400
          Re: can rPi drive PC-bidirectional Par-port? The Natural Philosopher <tnp@invalid.invalid> - 2013-04-08 10:21 +0100
            Re: can rPi drive PC-bidirectional Par-port? Rob Morley <nospam@ntlworld.com> - 2013-04-08 15:19 +0100
              Re: can rPi drive PC-bidirectional Par-port? The Natural Philosopher <tnp@invalid.invalid> - 2013-04-08 17:26 +0100
              Re: can rPi drive PC-bidirectional Par-port? "Stanley Daniel de Liver" <admin@127.0.0.1> - 2013-04-14 15:00 +0100
                Re: can rPi drive PC-bidirectional Par-port? Huge <Huge@nowhere.much.invalid> - 2013-04-14 14:25 +0000
  Re: can rPi drive PC-bidirectional Par-port? David <no@spam.please> - 2013-04-08 02:01 +0000
    Re: can rPi drive PC-bidirectional Par-port? Michael Black <et472@ncf.ca> - 2013-04-08 01:40 -0400

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