USB converters and old hardware

USB converters and old hardware

[Phil]

Thank you for reading this.

I have two old hardware items that I would like to put back into service.

The first is a Baycom style modem that of course does not work with USB to 
serial converters because of the non-standard way in which the modem 
interacts with the serial port. An acquaintance told me that genuine USB to 
serial converters are available but a Google search does not indicate this to 
be true. Can anyone suggest how I might be able to use this modem again?

The second question is more programming related and concerns a hardware 
item that used to operate via a parallel port. I thought a USB to parallel 
converter would easily solve this problem but it does not. The converter 
does allow me to use an old printer and it does cause /dev/parport0 to be 
generated. The problem is that ioctl(fd,PPCLAIM) now causes the following 
error message to be displayed:

"Parport claim: No such device or address" 

This indicates to me that the parallel converter does what it is intended to 
do, allow the use of old printers, but nothing else. Is there an alternative 
way to programme such a port? I've played with the outport C instruction 
briefly but I'm unsure of the base address of the port. Are genuine serial and 
parallel ports available for newer computers?

I'm reluctant to build new gear when the old stuff works perfectly.

-- 
Regards,
Phil

Re: USB converters and old hardware

[Mike McCarthy, W1NR]

There are many PCI and PCI-e cards with both types of ports that respond
like "real" serial and parallel ports. I generally buy the cheapest ones
I can find at mwave.com (they all seem to use the same chip) and have no
problems. No go for laptops. Best solution I have seen for laptops are
the legacy docking stations for the Dell Latitude line.

Mike, W1NR

Phil wrote:
> Thank you for reading this.
>
> I have two old hardware items that I would like to put back into service.
>
> The first is a Baycom style modem that of course does not work with USB to 
> serial converters because of the non-standard way in which the modem 
> interacts with the serial port. An acquaintance told me that genuine USB to 
> serial converters are available but a Google search does not indicate this to 
> be true. Can anyone suggest how I might be able to use this modem again?
>
> The second question is more programming related and concerns a hardware 
> item that used to operate via a parallel port. I thought a USB to parallel 
> converter would easily solve this problem but it does not. The converter 
> does allow me to use an old printer and it does cause /dev/parport0 to be 
> generated. The problem is that ioctl(fd,PPCLAIM) now causes the following 
> error message to be displayed:
>
> "Parport claim: No such device or address" 
>
> This indicates to me that the parallel converter does what it is intended to 
> do, allow the use of old printers, but nothing else. Is there an alternative 
> way to programme such a port? I've played with the outport C instruction 
> briefly but I'm unsure of the base address of the port. Are genuine serial and 
> parallel ports available for newer computers?
>
> I'm reluctant to build new gear when the old stuff works perfectly.
>
>   

Re: USB converters and old hardware

[Phil]

On Thu, 8 Apr 2010 08:20:56 pm Mike McCarthy, W1NR wrote:
> There are many PCI and PCI-e cards with both types of ports that respond
> like "real" serial and parallel ports. I generally buy the cheapest ones
> I can find at mwave.com (they all seem to use the same chip) and have 
no
> problems. No go for laptops. Best solution I have seen for laptops are
> the legacy docking stations for the Dell Latitude line.
> 

Thank you Mike,

I should have mentioned that I have a laptop. It's been a long time since I've 
owned a desktop computer and I didn't think of legacy cards. Are these 
cards compatible with the latest motherboards? It's an expensive option but 
worth considering.

-- 
Regards,
Phil

Re: USB converters and old hardware

[walter harms]

Phil schrieb:
> On Thu, 8 Apr 2010 08:20:56 pm Mike McCarthy, W1NR wrote:
>> There are many PCI and PCI-e cards with both types of ports that respond
>> like "real" serial and parallel ports. I generally buy the cheapest ones
>> I can find at mwave.com (they all seem to use the same chip) and have 
> no
>> problems. No go for laptops. Best solution I have seen for laptops are
>> the legacy docking stations for the Dell Latitude line.
>>
> 
> Thank you Mike,
> 
> I should have mentioned that I have a laptop. It's been a long time since I've 
> owned a desktop computer and I didn't think of legacy cards. Are these 
> cards compatible with the latest motherboards? It's an expensive option but 
> worth considering.
> 
Hi Phil,
there is an easy solution for laptops like this one here:
http://www.amazon.de/Delock-PCMCIA-ADAPTER-1x-SERIELL/dp/B000OQW562
http://www.amazon.de/Delock-PCMCIA-CardBus-1x-parallel/dp/B000N7BJO6

I have no idea about quality or linux drivers but PCMCIA with seriell or parallel
are available for many laptops. The question is more interessting if you want
both at the same time.

re,
 wh

Re: USB converters and old hardware

[IT2 Stuart Blake Tener, USNR]

ALCON,

I would suggest going with the KEYSPAN USB adapter, for some several  
reasons as follows:

1) They are entirely compatible with Linux, Windows, and MacOS  
(Keyspan USA-19)
2) This is a very high quality product
3) I believe Keyspan is now owned by TrippLite, a very respectable  
company as well.

Remember: "It's not you get what you pay for, but you do not get what  
you did not pay for!"


Stuart

Quoting "walter harms" <wharms@bfs.de>:

>
>
> Phil schrieb:
>> On Thu, 8 Apr 2010 08:20:56 pm Mike McCarthy, W1NR wrote:
>>> There are many PCI and PCI-e cards with both types of ports that respond
>>> like "real" serial and parallel ports. I generally buy the cheapest ones
>>> I can find at mwave.com (they all seem to use the same chip) and have
>> no
>>> problems. No go for laptops. Best solution I have seen for laptops are
>>> the legacy docking stations for the Dell Latitude line.
>>>
>>
>> Thank you Mike,
>>
>> I should have mentioned that I have a laptop. It's been a long time  
>> since I've
>> owned a desktop computer and I didn't think of legacy cards. Are these
>> cards compatible with the latest motherboards? It's an expensive option but
>> worth considering.
>>
> Hi Phil,
> there is an easy solution for laptops like this one here:
> http://www.amazon.de/Delock-PCMCIA-ADAPTER-1x-SERIELL/dp/B000OQW562
> http://www.amazon.de/Delock-PCMCIA-CardBus-1x-parallel/dp/B000N7BJO6
>
> I have no idea about quality or linux drivers but PCMCIA with  
> seriell or parallel
> are available for many laptops. The question is more interessting if you want
> both at the same time.
>
> re,
>  wh
> --
> To unsubscribe from this list: send the line "unsubscribe linux-hams" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
mobile: (310) 358-0202
Nextel: 124*233172*14 (direct connect)
e-mail: teners@bh90210.net

Re: USB converters and old hardware

[Douglas Cole]

I have to agree, I use the Keyspan adapters at work and at home.
They work for me as well, both the multiport devices as well as the
single port ones (USA19-HS)...
Port replicator for my work HP laptop gives me a 'real' serial port
(COM1 in Win32 land)...

Doug
N7BFS


On Tue, Apr 13, 2010 at 10:52 AM, IT2 Stuart Blake Tener, USNR
<teners@bh90210.net> wrote:
> ALCON,
>
> I would suggest going with the KEYSPAN USB adapter, for some several
> reasons as follows:
>
> 1) They are entirely compatible with Linux, Windows, and MacOS
> (Keyspan USA-19)
> 2) This is a very high quality product
> 3) I believe Keyspan is now owned by TrippLite, a very respectable
> company as well.
>
> Remember: "It's not you get what you pay for, but you do not get what
> you did not pay for!"
>
>
> Stuart
>
> Quoting "walter harms" <wharms@bfs.de>:
>
>>
>>
>> Phil schrieb:
>>> On Thu, 8 Apr 2010 08:20:56 pm Mike McCarthy, W1NR wrote:
>>>> There are many PCI and PCI-e cards with both types of ports that respond
>>>> like "real" serial and parallel ports. I generally buy the cheapest ones
>>>> I can find at mwave.com (they all seem to use the same chip) and have
>>> no
>>>> problems. No go for laptops. Best solution I have seen for laptops are
>>>> the legacy docking stations for the Dell Latitude line.
>>>>
>>>
>>> Thank you Mike,
>>>
>>> I should have mentioned that I have a laptop. It's been a long time
>>> since I've
>>> owned a desktop computer and I didn't think of legacy cards. Are these
>>> cards compatible with the latest motherboards? It's an expensive option but
>>> worth considering.
>>>
>> Hi Phil,
>> there is an easy solution for laptops like this one here:
>> http://www.amazon.de/Delock-PCMCIA-ADAPTER-1x-SERIELL/dp/B000OQW562
>> http://www.amazon.de/Delock-PCMCIA-CardBus-1x-parallel/dp/B000N7BJO6
>>
>> I have no idea about quality or linux drivers but PCMCIA with
>> seriell or parallel
>> are available for many laptops. The question is more interessting if you want
>> both at the same time.
>>
>> re,
>>  wh
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-hams" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
>
>
> --
> IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
> Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
> mobile: (310) 358-0202
> Nextel: 124*233172*14 (direct connect)
> e-mail: teners@bh90210.net
>
--
To unsubscribe from this list: send the line "unsubscribe linux-hams" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: USB converters and old hardware

[IT2 Stuart Blake Tener, USNR]

Doug,et alia:

The last Keyspan unit I had went to a customer (they needed it and  
paid a premium to buy my personal unit, something I had been  
preferential to avoid), and I never replaced it until I had an  
emergent need for one again, at which point I got one of the Prolific  
chipset based units. It works okay, and their drivers seem to be up to  
date, but I have a bit more trust in Keyspan to persistently provision  
MacOS drivers for newer variants of MacOS as time goes on.

One thing I am entirely interested in doing is getting a dual serial  
port USB cable, so I can use it for monitoring serial communications  
(data scope type functionality) between two devices (which I do have  
occasion to do sometimes). There is a piece of software that does data  
scope type functions (it is part of the "chirp" project for  
programming D-STAR radios) that does compile and function within the  
MacOS environment.

A unit from pimfg.com was recommended, but I never took the time to  
verify its compatibility level as far as Linux and MacOS goes (I  
always presume that these devices are Windows compliant for the most  
part), though pimfg.com generally has excellent prices on Chinese  
cable type stuff.

I was unaware of the multiport variants of the Keyspan, but I'd sure  
like to pick one up or review the specifications for it. I had also  
considered an FTDI based chipset device too, since their support  
across platforms seem to be very pervasive.


V/R,

Stuart, N3GWG



Quoting "Douglas Cole" <doug.n7bfs@gmail.com>:

> I have to agree, I use the Keyspan adapters at work and at home.
> They work for me as well, both the multiport devices as well as the
> single port ones (USA19-HS)...
> Port replicator for my work HP laptop gives me a 'real' serial port
> (COM1 in Win32 land)...
>
> Doug
> N7BFS
>
>
> On Tue, Apr 13, 2010 at 10:52 AM, IT2 Stuart Blake Tener, USNR
> <teners@bh90210.net> wrote:
>> ALCON,
>>
>> I would suggest going with the KEYSPAN USB adapter, for some several
>> reasons as follows:
>>
>> 1) They are entirely compatible with Linux, Windows, and MacOS
>> (Keyspan USA-19)
>> 2) This is a very high quality product
>> 3) I believe Keyspan is now owned by TrippLite, a very respectable
>> company as well.
>>
>> Remember: "It's not you get what you pay for, but you do not get what
>> you did not pay for!"
>>
>>
>> Stuart
>>
>> Quoting "walter harms" <wharms@bfs.de>:
>>
>>>
>>>
>>> Phil schrieb:
>>>> On Thu, 8 Apr 2010 08:20:56 pm Mike McCarthy, W1NR wrote:
>>>>> There are many PCI and PCI-e cards with both types of ports that respond
>>>>> like "real" serial and parallel ports. I generally buy the cheapest ones
>>>>> I can find at mwave.com (they all seem to use the same chip) and have
>>>> no
>>>>> problems. No go for laptops. Best solution I have seen for laptops are
>>>>> the legacy docking stations for the Dell Latitude line.
>>>>>
>>>>
>>>> Thank you Mike,
>>>>
>>>> I should have mentioned that I have a laptop. It's been a long time
>>>> since I've
>>>> owned a desktop computer and I didn't think of legacy cards. Are these
>>>> cards compatible with the latest motherboards? It's an expensive  
>>>> option but
>>>> worth considering.
>>>>
>>> Hi Phil,
>>> there is an easy solution for laptops like this one here:
>>> http://www.amazon.de/Delock-PCMCIA-ADAPTER-1x-SERIELL/dp/B000OQW562
>>> http://www.amazon.de/Delock-PCMCIA-CardBus-1x-parallel/dp/B000N7BJO6
>>>
>>> I have no idea about quality or linux drivers but PCMCIA with
>>> seriell or parallel
>>> are available for many laptops. The question is more interessting  
>>> if you want
>>> both at the same time.
>>>
>>> re,
>>>  wh
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-hams" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>>
>>
>> --
>> IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
>> Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
>> mobile: (310) 358-0202
>> Nextel: 124*233172*14 (direct connect)
>> e-mail: teners@bh90210.net
>>
>



-- 
IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
mobile: (310) 358-0202
Nextel: 124*233172*14 (direct connect)
e-mail: teners@bh90210.net

--
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More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: USB converters and old hardware

[Phil]

On Wed, 14 Apr 2010 03:37:03 pm Douglas Cole wrote:
> I have to agree, I use the Keyspan adapters at work and at home.
> They work for me as well, both the multiport devices as well as the
> single port ones (USA19-HS)...
> Port replicator for my work HP laptop gives me a 'real' serial port
> (COM1 in Win32 land)...
> 

Thanks Doug and Stuart for the extra information.

I have an unbranded duel port USB to serial converter that works perfectly 
with all sorts of serial devices except my Baycom clone modem. Can 
anyone confirm that the Keyspan converter will allow me to use my modem 
once again? The tripplite site does not say that their converter provides a 
genuine serial port and I suspect that it doesn't.

Even though Soundmodem works well I have found that my Baycom 
modem is far superior in that it will decode packets just above the noise 
level. Rather than fool around with USB to serial converters maybe I might 
be better off looking for a used TNC?

By the way, for those who suggested a PCMCIA option, my laptop does not 
have a PCMCIA slot.

-- 
Regards,
Phil

Re: USB converters and old hardware

[IT2 Stuart Blake Tener, USNR]

Phil, et alia:

> I have an unbranded duel port USB to serial converter that works perfectly
> with all sorts of serial devices except my Baycom clone modem. Can
> anyone confirm that the Keyspan converter will allow me to use my modem
> once again? The tripplite site does not say that their converter provides a
> genuine serial port and I suspect that it doesn't.

Firstly, I think you mean "dual" not "duel", since we are speaking of  
multiplicitous serial ports not a sword fight.

Secondly, a "genuine serial port" would be just that (a serial port  
implemented within hardware that is NOT a USB to serial port cable),  
and I would not think that anyone (a company or anyone on this list)  
would confirm that something is a "genuine serial port", when in fact  
it is not. To suggest someone would or should do so is ludicrous.

Teriarilly, the manner by which these devices function is to provision  
what could be considered as close to a "genuine serial port" as is  
possible. If one loads the driver, then attaches the appropriate  
USB/Serial cable to the system, then making a small test jig you can  
be assured of its functionality as proper.

To test weather a USB/serial port's functional capabilities, I have a  
DB-9 loopback connector (pins 2 and 3 are shorted together) that  
allows me to test such devices. Once connected, I go into a serial  
terminal software (such as Hyper Terminal for Windows) and attempt to  
type and see if the characters typed are echoed back.

If subsequent to such an exercise, functionality is apparent while  
using the baud rate and communications parameters that are appropriate  
for your application, then the device is functioning and works, period.

I have never seen any situation where a functional serial port/USB  
cable works with one device and not another, when all communications  
parameters are equal. However, that said, there are cases where if you  
set a modem to operate at say, above 56Kbps, and the USB/Serial cable  
only supports up to 9.6Kbps, then you might have a spot of trouble  
there, but this is not an incompatibility so much as a design  
limitation of the USB/Serial device vice the communications parameters  
of the device you wish to communicate with.

I believe most serial based Amateur Radio Packet Modems operate at a  
maximum speed of 9.6Kbps or 19.2Kbps (maybe even 56Kbps in some rare  
cases). Your device maybe configured differently, but I would suggest  
investigating this and the other communications parameters (such as  
parity, word length, stop bits, etc...).


> Even though Soundmodem works well I have found that my Baycom
> modem is far superior in that it will decode packets just above the noise
> level. Rather than fool around with USB to serial converters maybe I might
> be better off looking for a used TNC?
>

You may choose to suspect whatever you like, but a genuine serial port  
would be just that, not using a USB to Serial dongle, thus I doubt any  
company would even write such a thing. It seems you are rather  
frustrated, which I can understand entirely, but that does not relieve  
everyone from thinking with logic and addressing the problem with a  
measured and methodical manner by which to attempt its resolution.

Before we declare the USB/Serial device you have useless, let's  
conduct some of the testing proffered herein above in precedence to  
presuming it is the fault of the USB/Serial device. It might be  
working fine after all.


V/R,

Stuart, N3GWG


Quoting Phil <phillor@telstra.com>:

> On Wed, 14 Apr 2010 03:37:03 pm Douglas Cole wrote:
>> I have to agree, I use the Keyspan adapters at work and at home.
>> They work for me as well, both the multiport devices as well as the
>> single port ones (USA19-HS)...
>> Port replicator for my work HP laptop gives me a 'real' serial port
>> (COM1 in Win32 land)...
>>
>
> Thanks Doug and Stuart for the extra information.
>
> I have an unbranded duel port USB to serial converter that works perfectly
> with all sorts of serial devices except my Baycom clone modem. Can
> anyone confirm that the Keyspan converter will allow me to use my modem
> once again? The tripplite site does not say that their converter provides a
> genuine serial port and I suspect that it doesn't.
>
> Even though Soundmodem works well I have found that my Baycom
> modem is far superior in that it will decode packets just above the noise
> level. Rather than fool around with USB to serial converters maybe I might
> be better off looking for a used TNC?
>
> By the way, for those who suggested a PCMCIA option, my laptop does not
> have a PCMCIA slot.
>
> --
> Regards,
> Phil
> --
> To unsubscribe from this list: send the line "unsubscribe linux-hams" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
mobile: (310) 358-0202
Nextel: 124*233172*14 (direct connect)
e-mail: teners@bh90210.net
Quoting Phil <phillor@telstra.com>:

> On Wed, 14 Apr 2010 03:37:03 pm Douglas Cole wrote:
>> I have to agree, I use the Keyspan adapters at work and at home.
>> They work for me as well, both the multiport devices as well as the
>> single port ones (USA19-HS)...
>> Port replicator for my work HP laptop gives me a 'real' serial port
>> (COM1 in Win32 land)...
>>
>
> Thanks Doug and Stuart for the extra information.
>
> I have an unbranded duel port USB to serial converter that works perfectly
> with all sorts of serial devices except my Baycom clone modem. Can
> anyone confirm that the Keyspan converter will allow me to use my modem
> once again? The tripplite site does not say that their converter provides a
> genuine serial port and I suspect that it doesn't.
>
> Even though Soundmodem works well I have found that my Baycom
> modem is far superior in that it will decode packets just above the noise
> level. Rather than fool around with USB to serial converters maybe I might
> be better off looking for a used TNC?
>
> By the way, for those who suggested a PCMCIA option, my laptop does not
> have a PCMCIA slot.
>
> --
> Regards,
> Phil
> --
> To unsubscribe from this list: send the line "unsubscribe linux-hams" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
mobile: (310) 358-0202
Nextel: 124*233172*14 (direct connect)
e-mail: teners@bh90210.net

Re: USB converters and old hardware (in general)

[Dave Platt]

> I have never seen any situation where a functional serial port/USB cable
> works with one device and not another, when all communications
> parameters are equal. However, that said, there are cases where if you
> set a modem to operate at say, above 56Kbps, and the USB/Serial cable
> only supports up to 9.6Kbps, then you might have a spot of trouble
> there, but this is not an incompatibility so much as a design limitation
> of the USB/Serial device vice the communications parameters of the
> device you wish to communicate with.

There are some other issues which can be relevant, and which may
show up as incompatibilities between certain serial ports ("real"
or USB) and certain devices.

For one thing:  voltage.  "True" RS-232 signaling voltages are
bipolar, with a logic-1 being -3 to -12 volts with respect to
ground, and logic-0 being +3 to +12 volts.  The voltage range
between -3 and +3 is a no-sentient-beings'-land - it's
an undefined state.

Serial ports and adapters which want to be truly RS-232
compatible will generate output voltages which swing both
positive and negative.  There are specialized RS-232 driver
chips (the Maxim MAX232 and its cousins are the best known)
which can do this when powered from USB or a similar 5-volt
unipolar power bus - they have voltage doublers/inverters which
can ensure that they can swing their pins at least a few
volts below ground.

Many serial ports these days don't transmit "true RS-232" -
they swing their pins up to +5, and down to ground, but don't
pull the pins to a negative voltage.  They depend on the
receiving device being tolerant of this behavior... and in fact
a majority of serial port receiver circuits set their detection
threshold at somewhere around +1.5 volts, and treat a zero-volt
(ground-level) input as being equivalent to a negative voltage.

I strongly suspect that some inexpensive serial-port adapters
don't generate real RS-232 (negative output voltages).  These
may not work with some older peripherals which assume a true
RS-232 port, and require that the signals swing down well below
ground voltage.

"Parasitic" powering is another issue.  There are a number of
small external peripherals which don't have their own power
supplies, and expect to be able to "steal power" from the
RS-232 port itself... often from the RTS and DTR signals.
These devices may not work reliably if the RTS/DTR pins swing
only a few volts above ground, or if these pins have a high
output impedance and can't source more than a milliamp or
two of current before their voltage sags.

These sorts of voltage and current incompatibilities can
affect both "real" serial ports (e.g. UARTs hooked to the
ISA or PCI or PCMCIA busses) and USB serial-port dongles.
I've heard of devices that will work well with most older
desktop/server PCs, but which don't work with many laptops...
for precisely this reason.

I believe that the Baycom serial modem is probably one such
device.  According to the documentation I found at the
http://www.baycom.org/bayweb/tech/anst.htm page, this device
is parasitically powered from the DTR and RTS lines - it
expects to see a 12-volt level on these pins, and filters
and regulates this down to +5 in order to power its logic
circuitry.  In addition, it appears to assume that the
TX and RX pins are also swinging / to-be-swung +/-12 volts.

This device does *not* include a MAX-232 or similar RS-232
level shifter device, to buffer between its own internal CMOS
logic chips and an RS-232 bus... the documentation makes it
clear that they chose to save money by using a combination
of specific CMOS logic chips and discrete switching transistors.
This saved money, but it looks to me as if it had the side
effect of making the device very dependent on being hooked
to a "true" RS-232 port with high-voltage bipolar voltage
drive.

I rather strongly suspect that this device won't work
properly (without extensive hardware modifications) with any
5-volt-only "pseudo-RS-232" serial port, whether it be one in
a laptop or one in a USB dongle.  Furthermore, it probably
won't work with any serial port whose DTR/RTS pins have a
low drive capability (as I suspect is true for many serial
port USB dongles).

There may very well be serial-port dongles which have
"true" RS-232 outputs:  a MAX-232-type chip powered from
the USB 5-volt bus could swing its outputs to +/- 10 volts,
which would probably work OK, and such a device *could* have
enough drive power on the RTS/DTR pins to power the Baycom.

Unfortunately I can't recommend any specific brand... I haven't
tested for this.  Experimentation would be required.

I imagine it would be possible to build an intermediate
power/level-shifter box, which would sit between the USB
serial-port dongle and the serial modem.  A couple of 9-volt
alkaline batteries, and a few transistors to serve as
level converters, would convert the dongle's 5-volt
output signals to +/-9 signals, and provide enough power to
run the serial modem.

Re: USB converters and old hardware (Baycom in particular)

[Dave Platt]

Another possible gotcha here... the Baycom is being
used to transmit and receive AX.25 signals, which are
1200-bit/second *synchronous* data (HDLC), not asynchronous
data as a UART normally sends!  Although I don't have a
schematic of the device and am not certain how this is
being done, the description at the above page leads me to
believe that the host software is actually clocking the
data out, a bit at a time, by toggling the TXD pin at
the necessary data rate.

I'm not sure how this is being done... but it may not
be possible at all in a USB dongle!  If they're setting
the UART to some weird data rate, and then transmitting
asynchronous bytes (e.g. one byte transmitted for each
bit they want to send), then maybe it'll work if the
USB dongle is capable of supporting this nonstandard
data rate.

The other way that they might be doing this, is writing
a bit into the UART control registers which turns on and
off the "Send a long space signal now!" feature... in effect,
taking direct control of the TXD line.  If that's the case, I
don't thing that this can be done via a USB dongle (at least,
not for this application), for a critical reason:

-  USB transactions happen once per millisecond.  That's the
   resolution with which you can send commands to the USB
   dongle.

-  Sending 1200 bit/second data via this method would require
   changing the TXD pins setting every 1/1200'th of a second.

Hmmm... let's see...

The Linux kernel driver for the Baycom SER12 modem appears to
be doing some such sort of low-level port trickery... it
bypasses / overrides the standard serial port driver, does
direct register-level control of the UART (works only
with UARTs that are register-compatible with the 8250
and 16xxx family), and appears to be dependent on handling
one interrupt per bit transmitted.

This just isn't going to work over a USB dongle!

Re: USB converters and old hardware (Baycom in particular)

[Tomi Manninen]

Dave Platt wrote:

> Another possible gotcha here... the Baycom is being
> used to transmit and receive AX.25 signals, which are
> 1200-bit/second *synchronous* data (HDLC), not asynchronous
> data as a UART normally sends!  Although I don't have a
> schematic of the device and am not certain how this is
> being done, the description at the above page leads me to
> believe that the host software is actually clocking the
> data out, a bit at a time, by toggling the TXD pin at
> the necessary data rate.

In a "baycom modem" the data is sent and received through handshake
lines (DTR and CTS) and one (RTS) is used for PTT. TXD only serves as an
additional power source.

The software (baycom kernel driver) controls the lines directly using
UART register access. All timing is done by the CPU, not the serial port
hardware. Transmit is done using CPU timers and reception relies on
interrupts from handshake line state changes and calculating their time
differences.

In essence, a baycom modem uses the serial port as three general purpose
i/o lines to do bitbanging i/o with stringent timing requirements.

> This just isn't going to work over a USB dongle!

Definitely not.

/Tomi

Re: USB converters and old hardware (Baycom in particular)

[Adam Sampson]

Dave Platt <dplatt@radagast.org> writes:

> I'm not sure how this is being done... but it may not be possible at
> all in a USB dongle!

You might be pleasantly surprised. The FTDI USB-to-serial chips have a
bit-banging mode that's designed for doing this sort of thing, where you
can tell it to just clock a sequence of bits out to the pins (or read
one in) at a fixed rate. It'd need some software fiddling, of course,
and if you're going to that much effort I'd be tempted just to stick a
microcontroller in the way to give the modem a more convenient serial or
USB interface...

-- 
Adam Sampson <ats@offog.org>                         <http://offog.org/>

Re: USB converters and old hardware (Baycom in particular)

[Dave Platt]

Adam Sampson wrote:
> Dave Platt <dplatt@radagast.org> writes:
> 
>> I'm not sure how this is being done... but it may not be possible at
>> all in a USB dongle!
> 
> You might be pleasantly surprised. The FTDI USB-to-serial chips have a
> bit-banging mode that's designed for doing this sort of thing, where you
> can tell it to just clock a sequence of bits out to the pins (or read
> one in) at a fixed rate. It'd need some software fiddling, of course,
> and if you're going to that much effort I'd be tempted just to stick a
> microcontroller in the way to give the modem a more convenient serial or
> USB interface...

You're right, I hadn't thought about those particular USB chips in this
context.  They would require something other than the standard serial-port
host driver (i.e. a special driver, or at least some specialized ioctls
or other modes in the existing driver) since they aren't being used
as UARTs.

Yes, sticking a microcontroller between the modem chip and the USB
would certainly ease things.  That's the approach that the TNC-X
takes... it's a PIC micro hooked to a modem chip, which then
connects either to a serial port or to an on-board FTDI serial-to-USB
interface.  It speaks KISS over the host interface, and is thus
fairly easy to support on the host side.

Re: USB converters and old hardware

[Niall Parker]

Phil wrote:
> On Wed, 14 Apr 2010 03:37:03 pm Douglas Cole wrote:
>> I have to agree, I use the Keyspan adapters at work and at home.
>> They work for me as well, both the multiport devices as well as the
>> single port ones (USA19-HS)...
>> Port replicator for my work HP laptop gives me a 'real' serial port
>> (COM1 in Win32 land)...
>>
> 
> Thanks Doug and Stuart for the extra information.
> 
> I have an unbranded duel port USB to serial converter that works perfectly 
> with all sorts of serial devices except my Baycom clone modem. Can 
> anyone confirm that the Keyspan converter will allow me to use my modem 
> once again? The tripplite site does not say that their converter provides a 
> genuine serial port and I suspect that it doesn't.
> 
> Even though Soundmodem works well I have found that my Baycom 
> modem is far superior in that it will decode packets just above the noise 
> level. Rather than fool around with USB to serial converters maybe I might 
> be better off looking for a used TNC?

A Baycom style modem relies on a 'real' serial port because it _isn't_ 
using the serial port for typical asynchronous communications but rather 
  twiddling the control/data lines at a bit level via the registers of 
the once ubiquitous 8250 (and clones) UART. While it is conceivable that 
one could write a device driver for the USB chips that does the same 
thing (in particular the FTDI USB/serial chips have some options for bit 
level control), running the Baycom driver on top of an asynch emulation 
USB driver is going to be problematic with all the extra latencies 
involved. A fast enough PC might do it, but as you've found it often 
won't work at all.

A serial TNC on the other hand just talks plain ole asynch serial and 
will work fine.

				... Niall

Re: USB converters and old hardware

[IT2 Stuart Blake Tener, USNR]

Quoting "Niall Parker" <niall@ve7hex.ampr.org>:
> A Baycom style modem relies on a 'real' serial port because it  
> _isn't_ using the serial port for typical asynchronous  
> communications but rather  twiddling the control/data lines at a bit  
> level via the registers of the once ubiquitous 8250 (and clones)  
> UART. While it is conceivable that one could write a device driver  
> for the USB chips that does the same thing (in particular the FTDI  
> USB/serial chips have some options for bit level control), running  
> the Baycom driver on top of an asynch emulation USB driver is going  
> to be problematic with all the extra latencies involved. A fast  
> enough PC might do it, but as you've found it often won't work at all.

I did not realize that the Baycom modem used the serial port for this,  
and presumed from the originate poster wrote, that it was a  
communications type problem. That said, I would not be surprised if  
the Keyspan is capable of this type of usage anyway; they really do  
make a quality product.

However, if that is the case, then a USB type docking station might be  
a better choice. While they do work via USB, the serial port is "real"  
in most cases, and would provision the type of signaling most likely  
that he requires. eBay might have many choices that are priced  
reasonably.


V/R,

Stuart, N3GWG


> Phil wrote:
>> On Wed, 14 Apr 2010 03:37:03 pm Douglas Cole wrote:
>>> I have to agree, I use the Keyspan adapters at work and at home.
>>> They work for me as well, both the multiport devices as well as the
>>> single port ones (USA19-HS)...
>>> Port replicator for my work HP laptop gives me a 'real' serial port
>>> (COM1 in Win32 land)...
>>>
>>
>> Thanks Doug and Stuart for the extra information.
>>
>> I have an unbranded duel port USB to serial converter that works  
>> perfectly with all sorts of serial devices except my Baycom clone  
>> modem. Can anyone confirm that the Keyspan converter will allow me  
>> to use my modem once again? The tripplite site does not say that  
>> their converter provides a genuine serial port and I suspect that  
>> it doesn't.
>>
>> Even though Soundmodem works well I have found that my Baycom modem  
>> is far superior in that it will decode packets just above the noise  
>> level. Rather than fool around with USB to serial converters maybe  
>> I might be better off looking for a used TNC?
>
> A Baycom style modem relies on a 'real' serial port because it  
> _isn't_ using the serial port for typical asynchronous  
> communications but rather  twiddling the control/data lines at a bit  
> level via the registers of the once ubiquitous 8250 (and clones)  
> UART. While it is conceivable that one could write a device driver  
> for the USB chips that does the same thing (in particular the FTDI  
> USB/serial chips have some options for bit level control), running  
> the Baycom driver on top of an asynch emulation USB driver is going  
> to be problematic with all the extra latencies involved. A fast  
> enough PC might do it, but as you've found it often won't work at all.
>
> A serial TNC on the other hand just talks plain ole asynch serial  
> and will work fine.
>
> 				... Niall
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-- 
IT2 Stuart Blake Tener, USNR, N3GWG (Extra), MROP
Beverly Hills, CA / Las Vegas, NV / Philadelphia, PA / Washington, DC
mobile: (310) 358-0202
Nextel: 124*233172*14 (direct connect)
e-mail: teners@bh90210.net