GEMini Atari/GEMini_Atari_CD-ROM_Walnut_Creek_December_1993.iso/files/bbs/fn132bin/fdman/chapter.06

Text File | 1991-09-03 | 15KB | 397 lines

Chapter 6:  Modem Stuff                                                   86




6  Modem Stuff


   Modems  are finicky  beasts,  and  cajoling  them into  talking  to  your
Fnordadel properly can be  a tricky piece of business.  This  chapter, then,
deals with the  various modem configuration options in Fnordadel,  and gives
some tips on how to make a recalcitrant modem behave.



6.1  Basic Modem Requirements

   To run a Fnordadel, you  must have a modem possessing a modicum  of basic
features.  These are:

  o Must be able to auto-answer the phone.

  o Must be  able to respond  to DTR (Data  Terminal Ready) line control  by
    the computer.   DTR is  supposed to be pin  20 on the RS-232  connector.
    Ideally, the  modem should be  able to hang up  the phone, disable  auto
    answer, and  go to `command' mode when  the computer flips DTR  off (and
    reverse the above when DTR goes high).

  o Must  have the  CD  (Carrier Detect)  line tracking  the  status of  the
    carrier.  CD (or DCD) is supposed to be pin 8 on the RS-232 connector.

  o If  you  want  to  do  any  calling  out  (i.e.,  during  networking  or
    whatever), the modem must be able to autodial  the phone using a command
    string.

   Most modems are perfectly capable of all of the above.   If your modem is
advertised as being ``Hayes-compatible'',  then it *should* work fine.   The
DTR and CD  settings will likely have to  be adjusted, since most  modems do
not by default listen to  DTR and most leave the CD line high all  the time.
These behaviours  can be  changed either  by using  a DIP-switch  or in  the
software; it's almost always possible.

   STadel 3.3b, from  which Fnordadel is  descended, was advertised to  work
with the  following list of  modems, and there's no  reason to believe  that
we've introduced any incompatibilities:

  o Avatex 1200, 1200E, 1200HC, 2400HC

  o Everex 2400

  o FastComm 19200

  o Hayes 1200, 2400

  o Incomm 2400

  o MultiTech 1200, 2400

  o Prometheus 2400B2

  o Supra 2400



Chapter 6:  Modem Stuff                                                   87




  o Telebit Trailblazer 19,200

  o USR Courier 2400, HST 9600

The Fnordadel  developers both  use the Supra  2400; we've  been running  24
hours a  day for  a few  years now  and have had  no problems  with the  wee
beasties.  Your mileage may vary, of course.



6.2  Setting Up the Modem

   If your modem meets the above criteria, then we're off.   (If it doesn't,
then  go buy  a real  modem---1200  and 2400  baud Hayes  compatible  modems
are dirt  cheap these days.)   In  this section we'll  describe some of  the
`ctdlcnfg.sys' options for the modem.


6.2.1  Baud rate

   You  must tell  Fnordadel  the  highest  baud rate  at  which  the  modem
will function;  this  is accomplished by  setting the  variable #sysbaud  in
`ctdlcnfg.sys'.  #sysbaud can have any one of the following values:

0          300 bps only

1          300 and 1200 bps

2          300, 1200 and 2400 bps

3          300, 1200, 2400 and 9600 bps

4          300 up to 19200 bps

   Note that 4800 bps  is not supported.   The ST serial port will  do 4800,
but we've never heard of  a modem that will, other than ones that  will also
go faster.  If  for some reason you find yourself in dire need of  4800, see
Appendix A [Fnordadel Support], page 170.


6.2.2  Initialisation

   Hayes  compatible modems,  at  least, understand  a  set of  commands  to
control their behaviour.   Fnordadel requires that the modem be set up  in a
certain way; thus,  you must define a  command string which will be  sent to
the modem every time Fnordadel wants to reset the modem.   Simply put a line
like the following:

      #modemsetup "AT &C1 &D2 V0 E0 M0 Q0 X4 S0=1\r%10"

in  your   `ctdlcnfg.sys'.      The   example  above  will   work  on   many
Hayes-compatible modems.  The various parts mean:

  o The initial `AT' tells the modem that a command string is coming.



Chapter 6:  Modem Stuff                                                   88




  o `&C1  &D2' sets  up the  required behaviour  for  the CD  and DTR  lines
    (see Section  6.1 [Basic Modem Requirements], page  86).  If  your modem
    controls  CD  and DTR  with  hardware  switches, it  probably  will  not
    support these commands, so you may have to remove them.

  o `V0 E0 M0 Q0' selects numeric result  codes (see Section 6.2.3.2 [Result
    codes],  page 89),  turns off command  echoing, turns  off the  built-in
    speaker, and turns on result codes.

  o `X4'  tells the  modem to return  the full  range of  result codes  (see
    Section 6.2.3.2 [Result codes], page 89).

  o `S0=1' tells the modem to answer the phone on the first ring.

  o `\r' represents a carriage return, which must  be there to terminate the
    command string.

  o And  finally, `%10'  is a  special  notation which  causes Fnordadel  to
    pause for 10 tenths  of a second (i.e., one second).  This  is necessary
    for some  modems, which take  a comparatively long  time to process  the
    command  string.   (See  the front  of  `ctdlcnfg.doc' for  more on  the
    format of these sorts of string variables.)

   Please be warned  that your modem  may not recognise  some or all of  the
above codes;  they may  be different, or  absent, or whatever.   We've  seen
some pretty mental modem behaviour, so be sure to read your modem manual.

   A trick which has proved  useful with many modems is as follows:   If the
modem allows  you to  save its settings  in non-volatile RAM  (i.e., if  the
settings can  be preserved  when the  modem is  powered off),  then you  can
use a  terminal program of some  kind to manually set  up the modem the  way
Fnordadel wants  it, by  sending your  version of the  above command  string
to the  modem.   Then use the  command to save  settings (usually `AT&W'  or
something).  At this point you can simply use  `ATZ\r%10' as the #modemsetup
string;  `ATZ' has the  effect of resetting  the modem  to the saved  state.
The advantage of this is that the string is shorter,  so it can speed things
up a  bit, especially during  networking or auto-dialing  when the modem  is
being reset many times.


6.2.3  Baud-rate detection

   Fnordadel must be  able to detect  the baud rate  of incoming calls,  and
it has a  couple of ways to  accomplish this.   The first is by  searchbaud,
and the second  is using result codes.   Result codes are by far  the better
method, and since most modems can support the feature, we recommend it.



Chapter 6:  Modem Stuff                                                   89




6.2.3.1  Searchbaud

   If you  define  the `ctdlcnfg.sys'  variable #searchbaud  to be  `1',  it
will  cause Fnordadel  to loop  through the  range of  supported baud  rates
(as defined by  #sysbaud; see Section 6.2.1  [Baud rate], page 87),  waiting
one-half  second at  each  rate  for a  carriage  return (`<CR>')  from  the
caller.   The upshot of this is that  callers must hit `<CR>' once  or twice
when they connect with the BBS.

   If #searchbaud  is `0',  then your BBS  will work  at *only* the  highest
baud  rate represented  by  #sysbaud.    This is  last-resort  stuff,  kids.
You  should normally  run with  #searchbaud  set to  `1' unless  your  modem
absolutely  fails to  properly detect  other speed  connections.   (If  your
modem is this stupid, it might be time to consider getting another one.)

   The  variable  #connectprompt  modifies  the  behaviour   of  #searchbaud
slightly;  if defined to  be `1', it  causes Fnordadel  to loop through  the
baud rates,  spitting out a  prompt which says  ``Type return'' and  waiting
for a `<CR>'  for a while;  it does all this  until the user hits `<CR>'  at
some baud rate, or until it gives up.

   Anyway, this is  all pretty ugly, really; a  far better method is  to use
result codes.


6.2.3.2  Result codes

   Most modems,  Hayes-compatible ones  included, will  send a  code to  the
computer when  they pick  up a  carrier;  furthermore, they  can usually  be
configured  to  return a  different  code  depending  on the  speed  of  the
connection.  We utilise this to our advantage.

   There is  a `ctdlcnfg.sys'  variable for  each baud  rate that  Fnordadel
supports (#reply300 through  #reply19200) which you should set to  match the
string that  your modem returns  when it connects  at that baud  rate.   For
example:

      #reply300 "1"
      #reply1200 "5"
      #reply2400 "10"

are the usual settings for a Hayes-compatible 2400-baud modem.   (As always,
your mileage may vary.)

   Please note that  the defined reply strings  must be sent (by the  modem)
terminated with  a carriage return;  however, don't put  `\r' in the  #reply
strings.  (i.e.,  if the 300 baud reply  sent from the modem is `1\r',  use
`#reply300 "1"'.)

   If  you've  got  the  #reply  strings  defined  in  `ctdlcnfg.sys',  then
Fnordadel will use the  result code method instead of the  searchbaud stuff.
You must have a  #reply string for each permissible baud rate (i.e.,  if you
defined `sysbaud  1', then  you need  a #reply300 and  a #reply1200  defined
before Fnordadel will use the result code method.)



Chapter 6:  Modem Stuff                                                   90




   Note also  that  you must  have the  modem  set up  to  return the  codes
properly.  See Section 6.2.2 [Initialisation], page 87.


6.2.3.3  2400-baud operation

   Many 2400-baud modems  have a slight quirk.   They will not connect  with
a 2400 baud  caller unless they have  been initialised with the serial  port
set at 2400  baud; they will, however,  connect with any lower baud  rate no
matter what speed  they're initialised at.  We  don't know why this is;  but
if your modem is  like this, there's a `ctdlcnfg.sys' parameter  (well, two,
actually) which will help.

   Simply define the variable #init-speed  to be the baud rate at  which the
modem should  be initialised; the  permissible values are  the same as for
#sysbaud (see  Section 6.2.1  [Baud rate],  page 87).   In  the case of  the
quirky 2400 baud modems, put `init-speed 2' and the problem will go away.

   Another way of  fixing it is to  define #hs-bug to be  `1'.  This  causes
Fnordadel to initialise the modem at the highest  supported baud rate, which
is specified by #sysbaud.  Either method works.


6.2.3.4  Connect delay

   Some modems,  we understand, will  croak if a character  is sent to  them
too quickly after they  connect with an incoming caller.  This  could happen
if you've  got both searchbaud and  connectprompt set.   If it does  happen,
then set connectdelay to  be the number of seconds to wait after  carrier is
first detected, before sending anything.


6.2.4  Dialing out

   If you  want  to do  any networking,  or if  you  just want  to use  your
Fnordadel as a terminal  program, then you have to tell it some  stuff about
how to make your modem dial the phone.


6.2.4.1  The dialing commands

   The   relevant  `ctdlcnfg.sys'   variables   are  #calloutprefix   and
#calloutsuffix.   As  you'd expect, they  should be  defined as the  strings
used to start and end a dialing command.  The string  sent to the modem will
consist of:

      <calloutprefix><number><calloutsuffix>

For Hayes-compatible modems, the following settings work:

      #calloutprefix "ATD"
      #calloutsuffix "\r"

   An optional `T'  or `P' may be put  after `ATD' to specify Touch-Tone  or
Pulse (rotary) dialing.   If your modem is not standard Hayes, then  look it
up in the manual.



Chapter 6:  Modem Stuff                                                   91




6.2.4.2  Long-distance dialing

   If the variable #usa is  defined to be `1', then Fnordadel assumes  it is
in North America  and will form the  dial string for a long-distance  number
as follows:

      <calloutprefix>1<area code><number><calloutsuffix>

   If #usa is `0', Fnordadel will simply spit the number out as-is.


6.2.4.3  Timing

   Two more `ctdlcnfg.sys' variables are used to tell Fnordadel  how long to
wait for a connection  when dialing out.  The two variables  are #local-time
and #ld-time; they default to 25 seconds and 50  seconds respectively.  (The
time used for long-distance (``ld'') dialing is longer  because of delays in
the phone system.)



6.2.4.4  A speed-up

   If  you define  the  variable  #hayes  to be  `1',  then  Fnordadel  will
blithely assume  that the  modem returns `3'  for `NO  CARRIER' and `7'  for
`BUSY' when it's dialing out.   This is a useful kludge to speed  up dialing
out;  otherwise, you've  got to  wait for the  defined amount  of time  (see
Section 6.2.4.3  [Timing], page  91) to pass  before Fnordadel will  realise
that the call is not going to be successful.

   Please note that defining #hayes  has no other effect; it will  not cause
Fnordadel to assume anything else about the nature of your modem.


6.3  High-Speed Modems

   Getting high-speed  modems (9600  bps and  up) to work  with your  system
isn't quite as straight  forward as with lower-speed units.  For  one thing,
if you're using TOS 1.4 or higher, there is a  glitch that prevents hardware
(RTS/CTS)  flow control  from working.    To fix  the problem,  you need  to
install tos14fx2.prg in your AUTO folder.  See Section  13.1 [Things to Make
Fnordadel Work or Work Better], page 151.

   For another thing, high-speed  modems are typically able to talk  to your
Atari at a  fixed speed (usually 19,200  bps), and handle the online  user's
varying connect  speed themselves.   To make this  work properly, you  don't
want your  Fnordadel to  try altering the  serial port  speed; instead,  you
want it  locked at a  fixed setting.   This is done  by setting #sysbaud  to
the speed  at which  you wish  the system  locked, #searchbaud  to `0',  and
all the  result code strings to  the null string, "".   See Section  6.2.3.1
[Searchbaud], page 89, and Section 6.2.3.2 [Result codes], page 89.

   Two side-effects of  port locking are  that file transfer time  estimates
will  be out  of  whack, and  the  `calllog.sys' file  will show  all  users
connected at the locked speed.  These problems will be fixed some day.



Chapter 6:  Modem Stuff                                                   92




6.4  Common Modem Problems

  o "The modem won't work properly at 2400 baud!  Help!"

    See Section 6.2.3.3 [2400-baud operation], page 90.

  o "What happens if I turn the modem off while someone is online?"

    Nothing  bad.     Because you've  got  the  #modemsetup  string  defined
    (you  *have*  got  it  defined,  right?    If  not,  see  Section  6.2.2
    [Initialisation],  page 87),  the  BBS will  simply detect  the loss  of
    carrier  and immediately reinitialise  the modem  properly for the  next
    caller, logging the previous caller off.

  o "My Blistering-Speed-of-Deth  153,600 baud modem  won't work right  with
    Fnordadel!  Help!"

    Please send  us two of the  modems in question,  and we promise to  have
    Fnordadel working flawlessly with them right away!