Программа Сервисный Центр
CD32 Keyboard to Serial Interface 2
Date: Thu, 20 Oct 1994 11:07:00 +0100
From: Klaus_Hegemann@punk.fido.de (Klaus Hegemann)
Subject: Re: Using Auxiliary Port as Serial Port
Message-ID: <b1990b05%fidonet@p29.f113.n2452.z2.fidonet.org>
References: <8df67bba@coyote.dres.dnd.ca>
Newsgroups: comp.sys.amiga.cd32
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Hi Stan !
 s> I understand that you can use the auxiliary port (keyboard) as an
 s> RS-232 port and that this is what sernet does.  But when I look at
 s> the pinout, there is only clock and data signals, not ser-in and
 s> ser_out.  What am I missing here?
Well, I think you refer to the A4000"s kb.jack pinout. It"s "almost"
the same as you can find at the cd32. But the difference is, tataa..:
on the cd32 there are additional serial-interface-signals connected
to the AUX-jack. You can find them at the former unused pins.
The mess is, that the (serial-) signals carry [negated] TTL-level.
As a result, you have to make sure that there is a level-conversion
before you connect them to other computers. Without you surely kill
your cd32.
The cd32-FAQ shows a rather complex (but quite correct) way to do this.
(Aehm, the level-conv., of course ;-)
If you plan to connect the CD32 with other Amigas then I found out a
rather easyer/cheaper way to solve that:
Amiga                    | |                         Amiga CD32
             TxD o-------| >|---.
level: RS232             |/ |   |                     level: /TTL
-12V..+12V            D1        |                     0V..+5V
                               .-.
                               | |
                               | |        IC1
                             R1| |   """"""""
                               `-"   "  _   "
                                |    " |   "
                                *------|  O-------->o /RxD Pin6
                                |    " |_/  "
                               .-.   "      "
                               | |   "      "
                               | |   "      "
                             R2| |   "      "
                               `-"   "      "
                                |    "      "
                                |    "      "
                                |    "      "
                               ===   "      "
                               ///   "   _  "
                                     "  / | "
              RxD o<-------------------O  |---------o /TxD Pin2
                                     "  _| "
                                     "      "
                                     """"""""

              GND o-----------------------*---------o GND
                                          |
                                     """""|""
                                     " o  o "
                                     " |7 14"
                                     ""|""""" IC1
                                       |
              +5V o--------------------"
the pros. and cons.  ([1]this solution ./. [2]max232-sol. (->FAQ) )

pros.[1]:  easy to solder
           cheap
           fits within a SUB-D 25 plug
           does not consume CD32 +5V power ;-)

cons: "dirty" solution; i.e. circuitry makes use of the 1488/89 tolerances
      you may only connect Amiga-computers to your cd32 when using THIS
      [1] circuitry - since they all use the 1488/89 chip set.
      PCs "may" work, too. But interface board must contain 1488/89 chip
      set.
      I do believe that this will work on all Amigas -I tested it at least
      on 3 different Amiga-models, however, there is still no guarantee
      that this will work on yours.

However, I use both interface-types since about 6 months.  There has
been no problem yet.

 s> Also, has anyone made their own connector to the expansion port to
 s> pull off the RGB signals?  I"d appreciate hearing of your experience.

Yea, does work fine.  In use for about 6 months; and still no probs, too.
For details refer to the cd32-faq.

I am not quite sure about the cd32-pin numbers, just take a look in the
faq.

bis den bald
Klaus

[---------------------------------------------------------------------------]
Date: Fri, 21 Oct 1994 14:55:00 +0100
From: Klaus_Hegemann@punk.fido.de (Klaus Hegemann)
Subject: Re: [2]Using Auxiliary Port as Serial Port
Message-ID: <b1a112f9%fidonet@p29.f113.n2452.z2.fidonet.org>
References: <b1990b05%fidonet@p29.f113.n2452.z2.fidonet.org>
Newsgroups: comp.sys.amiga.cd32
X-Comment-To: sburton@dres.dnd.ca (All)
Organization: Fido.DE domain gateway (IN e.V.)
Lines: 117
X-Gateway: FIDOGATE 3.8.0
X-FTN-Tearline: CrossPoint v3.02
X-FTN-Origin: Josef Matula for President (2:2452/113.29)
X-FTN-Domain: Z242@fidode
X-FTN-Seen-By: 1000/1 150 600 601 2000/1 2452/113 3000/1 4900/99 6000/0
X-FTN-Path: 1000/600 1
Hi!

"updated info:"
       Amiga 500,2000,1200,...

       level: RS232
       -12V..+12V

                          | |                         Amiga CD32
              TxD o-------| >|---.
              Pin2        |/ |   |                     level: /TTL
                       D1        |                     0V..+5V
                       1N4001   .-.
                                | |
                                | |        IC1 7400
                             R1 | |   ........
                            (*) `-"  1:  _   :
                                 |   ___|   :3
                                 *--*___|  O-------->o /RxD Pin6
                                 |    : |_/  :
                                .-.  2:      :
                                | |   :      :
                                | |   :      :
                             R2 | |   :      :
                            (*) `-"   :      :
                                 |    :      :
                                 |    :      :
                                 |    :      :
                                ===   :      :
                            GND ///   :   _  :4
                                     6:  / |____
               RxD o<-------------------O  |____*----o /TxD Pin2
               Pin3                   :  _|
                                      :      :5
                                      :.......

               GND o---------------*-----------------o GND Pin3
               Pin7                |
                                   |  ........
                                   | 7:      :IC1
                                   *--:GND   :
                                   | 9:      :
                                   *--:     :
                                   |10: |not :
                                   *--: |used:
                                   |12: |    :
                                   *--: |    :
                                   |13: |    :14
                                   `--: / +5V:-.
                                      :......: |
                                               |
                                               |
               +5V o---------------------------"
               Pin4

            shield o=======================! [n.c.] o shield
               Pin1

The RS232-TxD-signal carries +12V or -12V level. As the first step
in conversion the diode D1 blocks if the signal drops to -12V.
In this case the voltage divider (R1,R2) is only connected with
GND potential. So the gate input carries GND level, too.
When the RS232-TxD-signal changes to +12V the diode will pass it
through and the voltage divider now provides a +5V-level signal to
the gate input.
The backward conversion consists of simple negation of the cd32"s
/TxD signal. In fact there is no level conversion.
While the conversion for the received signal does
work proper with any RS232 opponent, the sended
signal furthermore carries TTL-level.
The opponent hardware tries to regain the TTL-level signal from
its "RS232" input. The conversion unit handles the provided
pseudo RS232-type signals correct (as we want ist to be:-).
(*) voltage divider R1-R2:

   U                      U      = 12V    U   = 5V
    R1+R2     R1+R2        R1+R2           R2
   ------  =  -----
   U            R2
    R2

                               U
                                R1+R2
   I      = 5 mA  ==> R1+R2 = ------   = 2400 Ohm
    R1+R2                      I
                                R1+R2

                     (R1+R2) * U
                                R2
   U   = 5V ==> R2 = -------------  = 1000 Ohm; R1= 1400 Ohm
    R2                  U
                         R1+R2

R1=1500 Ohm
R2=1000 Ohm ==> I=4.8 mA ==> U(R2)=4.8 V   ..  will be OK

IC1 = 74LS00  (4 NAND gates)
D1 = e.g. 1N4001
have fun !
be careful; I am in no way responsible for any damage that may result.
CU
bis den bald
Klaus                    klausi@punk.fido.de

 
 
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