2 Jun
2009
2 Jun
'09
11:39 a.m.
On Tue, June 2, 2009 4:45 am, Johnny Billquist wrote:
He's not talking about powering the device, he's talking about driving
the signal lines. Their input impedance isn't infinite, you know!
-Dave
--
Dave McGuire
Port Charlotte, FL
USB only
guarantees to supply 100 milliamps. Up to 500 mA can be
negotiated with the controller, depending. Might your older device
depend on more amps than the USB adapter can supply?
Huh? The RS-232-port isn't supposed to deliver any power at all. Some
devices admittedly abused the RS-232 by using something like DTR to
actually supply the power needed to drive the thing, but that is abuse.
But I'd be surprised if a circa-70s modem was ever designed to use the
power from the RS-232 port to drive the modem itself. I'd expect it to
have an external power supply. 
2 Jun
2 Jun
9:52 p.m.
At 10:39 AM 6/2/2009, Dave McGuire wrote:
He's not talking about powering the device,
he's talking about driving
the signal lines. Their input impedance isn't infinite, you know!
I think there has been other threads here regardng the hit-or-miss
nature of these USB-to-serial adapters. I know when I needed one
to sync a Palm, I couldn't find one that did it right. I think
I hit my head against three $30 adapters to no avail, but this
was four-five years ago.
I'm not smart enough to talk about reactance, but I can tell you they're
not quite the same. It would stand to reason that a 30-year-old modem
might've been developed to talk to its contemporaries.
- John
10:53 p.m.
New subject: USB/serial adapters (was: cctalk Digest, Vol 70, Issue 3)
In article <6.2.3.4.2.20090602204549.03f8b810 at mail.threedee.com>,
John Foust <jfoust at threedee.com> writes:
I think there has been other threads here regardng the
hit-or-miss
nature of these USB-to-serial adapters. I know when I needed one
to sync a Palm, I couldn't find one that did it right. I think
I hit my head against three $30 adapters to no avail, but this
was four-five years ago.
I've used them to talk to terminals and had no problems.
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://www.xmission.com/~legalize/book/download/index.html>
Legalize Adulthood! <http://blogs.xmission.com/legalize/>
3 Jun
3 Jun
11:49 a.m.
New subject: USB/serial adapters (was: cctalk Digest, Vol 70, Issue 3)
On Jun 2, 2009, at 10:53 PM, Richard wrote:
Yep. I use them all day, every day, and have never had the
problems I've heard people complain about here. Right now on my main
desktop machine, I have a USB<->serial adapter connected to an ARM9
development board, another connected to a homebrew Z80 SBC, another
connected to a PDP-11/83, and yet another connected to a PDP-11/70.
They all work wonderfully. I use Keyspan adapters.
Admittedly, though, I've not tried my old A-J acoustic modem.
Some people whine about they Keyspan adapters being too
expensive...they may be having problems because they bought some
cheap $5 adapters. The last Keyspan unit I purchased cost me (I
think) about $30.00, and I bought it about six years ago.
Complaining about $30.00 over six years is being too damn cheap, even
for the cheapskates around here.
On my Sun Ray thin clients, I use Edgeport quad-port adapters.
They exhibit some latency (that may be due to the Sun Ray USB
encapsulation though), but they work pretty well otherwise. The
serial ports show up as devices on the Sun Ray host system.
-Dave
--
Dave McGuire
Port Charlotte, FL
I think there
has been other threads here regardng the hit-or-miss
nature of these USB-to-serial adapters. I know when I needed one
to sync a Palm, I couldn't find one that did it right. I think
I hit my head against three $30 adapters to no avail, but this
was four-five years ago.
I've used them to talk to terminals and had no problems. 
4 Jun
4 Jun
12:56 a.m.
New subject: USB/serial adapters (was: cctalk Digest, Vol 70, Issue 3)
I think there has been other threads here regardng the
hit-or-miss
nature of these USB-to-serial adapters. I know when I needed one
to sync a Palm, I couldn't find one that did it right. I think
I hit my head against three $30 adapters to no avail, but this
was four-five years ago.
I've used them to talk to terminals and had no problems. 
12:49 p.m.
New subject: USB/serial adapters (was: cctalk Digest, Vol 70, Issue 3)
On Wed, 3 Jun 2009 11:49:27 -0400
Dave McGuire <mcguire at neurotica.com> wrote:
Some people whine about they Keyspan adapters being
too
expensive...they may be having problems because they bought some
cheap $5 adapters.
I bought four different 5 EUR USB-RS232 adapters. They have all
the
same chip inside and just work on NetBSD:
uplcom2: Prolific Technology Inc. USB-Serial Controller, rev 1.10/3.00,
addr 2
Though I still have to connect them to my HP 54720D scope to chek if
they provide proper voltage levels.
The last Keyspan unit I purchased cost me (I think)
about $30.00
I spend 30 EUR in a cheap and generic PCI quad RS232 adapter card.
Again: Just worked with NetBSD.
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
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days inactive
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days old
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doug＠stillhq.com -
jfoust＠threedee.com -
jkunz＠unixag-kl.fh-kl.de -
legalize＠xmission.com -
mcguire＠neurotica.com