Cheap external modem

Cheap external modem

Post by DB76543 » Thu, 27 May 1999 04:00:00



Where can I get a cheap linux compatible modem (external preferred)?  I would
like to get one under $70 if possible.  I found a list of inexpensive linux
compatible stuff at http://www.math.sunysb.edu/~comech/tools/CheapBox.html and
wondered if anyone has had any problems with the modems listed on that site?

David Bell

Please don't email me just reply on the board.

 
 
 

Cheap external modem

Post by Joshy Georg » Fri, 28 May 1999 04:00:00


Try Filand 56K Fax external modem.
I'm using it. Also note that it won't work on ttyS0, but on ttyS1 it's
alright.
This modem costs around HK$400 here in HongKong. That's almost US$52.

Joshy.

Quote:> Where can I get a cheap linux compatible modem (external preferred)?  I
would
> like to get one under $70 if possible.  I found a list of inexpensive
linux
> compatible stuff at http://www.math.sunysb.edu/~comech/tools/CheapBox.html
and
> wondered if anyone has had any problems with the modems listed on that
site?

> David Bell

> Please don't email me just reply on the board.


 
 
 

Cheap external modem

Post by Johan Kullsta » Fri, 28 May 1999 04:00:00



> Try Filand 56K Fax external modem.
> I'm using it. Also note that it won't work on ttyS0, but on ttyS1 it's
> alright.

that's odd.  being an external modem, how would it know it what ttySn
it was* off of?  is there some asymmetry in the linux serial
drivers or hardware difference between your serial ports?

--
johan kullstam

 
 
 

Cheap external modem

Post by Henrik Carlqvis » Fri, 28 May 1999 04:00:00




> > Try Filand 56K Fax external modem.
> > I'm using it. Also note that it won't work on ttyS0, but on ttyS1
> > it's alright.

> that's odd.  being an external modem, how would it know it what ttySn
> it was* off of?  is there some asymmetry in the linux serial
> drivers or hardware difference between your serial ports?

I would guess that he has some other device that shares IRQ 4, like
something connected to ttyS2.

regards Henrik

--
spammer strikeback:


 
 
 

Cheap external modem

Post by Joshy Georg » Tue, 01 Jun 1999 04:00:00


I have only this modem using serial ports. My mouse is a PS/2 mouse.
The modem documentation specifically mentions that COM2 is the recommended
port to connect to under Windows, for reasons beyond my guess!
The motherboard I'm using is an Intel one with built in sound card. Could
that be the reason?
Anyway, I have not tried to configure the sound card, and Linux did not
detect it while installation.
Joshy.



> > > Try Filand 56K Fax external modem.
> > > I'm using it. Also note that it won't work on ttyS0, but on ttyS1
> > > it's alright.

> > that's odd.  being an external modem, how would it know it what ttySn
> > it was* off of?  is there some asymmetry in the linux serial
> > drivers or hardware difference between your serial ports?

> I would guess that he has some other device that shares IRQ 4, like
> something connected to ttyS2.

> regards Henrik

> --
> spammer strikeback:



 
 
 

Cheap external modem

Post by David » Tue, 01 Jun 1999 04:00:00



> I have only this modem using serial ports. My mouse is a PS/2 mouse.
> The modem documentation specifically mentions that COM2 is the
> recommended port to connect to under Windows, for reasons beyond my
> guess!

Ya got me.  Doesn't make sense to me either.  A PS/2 mouse normally uses
IRQ 12, so it shouldn't conflict with either serial port.

I've been using external modems at various speeds on COM1 for over 5
years now with DOS, OS/2, Win 3.1, Win95, WinNT and Linux, and haven't
had a problem with any of them

If you've got an old serial interface with 8250 UART chips, you may have
serious problems running the port faster than 9600bps, but you'd need a
really old system to have that problem today.  Every Pentium-or-better
motherboard with built-in serial ports I've ever seen has 16550AFN (or
compatible) serial ports, which are reliable at 115200bps (where most
56K modems like to run at.)

Quote:> The motherboard I'm using is an Intel one with built in sound
> card. Could that be the reason?

You'll have to find out what interrupts and ports the sound card is
using.  If it's a clone of the Creative Labs SoundBlaster, the factory
defaults will be:

        Digital Sound I/O port: 0x0220 - 0x022F
        MIDI UART I/O port:     0x0330 - 0x0331
        FM Synthessi I/O port:  0x0388 - 0x038B
        Low-DMA channel:  1
        High-DMA channel: 5
        IRQ: 7

You will want to make sure to change the IRQ to something else, since 7
is used by your printer interface.  This IRQ sharing works OK under DOS
and Windows only because those platforms don't normally use the IRQ when
printing to the parallel port.

The standard resources used by serial ports (so you can check for
conflicts) are:

        COM1: port 0x03F8-0x03FF, IRQ 4
        COM2: port 0x02F8-0x02FF, IRQ 3

There are no official standard assignments for COM3 and COM4, but these
are often used:

        COM3: port 0x03E8-0x03EF, IRQ 4
        COM4: port 0x02E8-0x02EF, IRQ 3

Note, that these definitions cause conflicts between COM1/COM3 and
between COM2/COM4.  This can cause problems.  Making sure that you use
other IRQs for the extra ports will prevent those problems.

-- David

 
 
 

Cheap external modem

Post by Henrik Carlqvis » Tue, 01 Jun 1999 04:00:00



> The modem documentation specifically mentions that COM2 is the
> recommended port to connect to under Windows, for reasons beyond my
> guess!

The only reason is that some mouse drivers only work with COM1 in
windows. Then there is only COM2 left to use as COM3 and COM4 are almost
unusable sharing interrupts with other com ports. Have you tried to
connect the modem to COM1? What kind of error did it give? Did you
change /dev/modem to point to /dev/ttyS0 or /dev/cua0?

regards Henrik
--
spammer strikeback:


 
 
 

Cheap external modem

Post by Johan Kullsta » Wed, 02 Jun 1999 04:00:00




> > The modem documentation specifically mentions that COM2 is the
> > recommended port to connect to under Windows, for reasons beyond my
> > guess!

> The only reason is that some mouse drivers only work with COM1 in
> windows. Then there is only COM2 left to use as COM3 and COM4 are almost
> unusable sharing interrupts with other com ports. Have you tried to
> connect the modem to COM1? What kind of error did it give? Did you
> change /dev/modem to point to /dev/ttyS0 or /dev/cua0?

sound logical.  however, if it works now, don't mess with it!

--
                                           J o h a n  K u l l s t a m

                                              Don't Fear the Penguin!

 
 
 

Cheap external modem

Post by Joshy Georg » Fri, 04 Jun 1999 04:00:00




> > The modem documentation specifically mentions that COM2 is the
> > recommended port to connect to under Windows, for reasons beyond my
> > guess!

> The only reason is that some mouse drivers only work with COM1 in
> windows. Then there is only COM2 left to use as COM3 and COM4 are almost
> unusable sharing interrupts with other com ports.

That's quite a good explanation. Thanks.

Quote:> Have you tried to
> connect the modem to COM1? What kind of error did it give? Did you
> change /dev/modem to point to /dev/ttyS0 or /dev/cua0?

Amazingly, there were no error/warning messages!
I've used the 'Modemtool' under X's Control panel to make that link between
/dev/modem and /dev/ttyS0. Then used 'setserial /dev/ttyS0 autoconfig -v' to
check the ttyS0 settings. It reported "dev/ttyS0, UART:16550A, Port: 0x03f8,
IRQ: 4". Everything appeared normal.

 In 'minicom' I've tried many different combinations of init strings for
modem, but it simply refused to initialise. I never saw and "OK". But it was
sensing incoming calls, and prompted 'RING' at the 'minicom' terminal,
whenever there was one.
Any way, after two days, I gave up and tried ttyS1, and without much
problems I can connect to my ISP now.
Looking at /proc/interrupts did not give me any clue about any conflicting
irq settings!

With some help, I think I'll be able to figure out what went wrong with
ttyS0.
Your expert comments are much appreciated.

Joshy.

> regards Henrik
> --
> spammer strikeback: