Re: Demise of the COM port?
From: Jim Granville (no.spam_at_designtools.co.nz)
Date: 03/20/04
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Date: Sat, 20 Mar 2004 12:49:14 +1300
Viktor Kesler wrote:
> rickman <spamgoeshere4@yahoo.com> wrote in message news:<405A4DA3.3260FD95@yahoo.com>...
>
>
>>For example, the give away Cypress PSOC invention board uses USB. One
>>chip, likely cheaper than an RS-232 converter, provides the USB
>>interface. The connectors come in two flavors, small and tiny. It was
>>designed from the get-go (not gecko) to be low cost and yet run at 12
>>Mbps at 5 meters. I like it and I will be getting very used to it.
>>
>
>
> Yes, but we need 9600Bd at up to 1km with a few kV isolation.
> We use a 20mA-loop dongle stuck into the PC COM port. Works like a
> charm and the only thing that can burn it is a lightning strike - and
> even then the PC never gets damaged, only the dongle.
>
> So, building USB into our product doesn't make sense because it's not
> near the PC. We've already got an ethernet tcp/ip module, but that's
> not much use if there isn't already a LAN running around the place.
>
> Using USB/RS232 converters seems to be the only option, but the few
> types we tested cause delays so we had to tweak our PC software to get
> them to work.
>
> The question is, will all USB/RS232 converters behave in the same way?
> I'm thinking of delays and out-of-the-ordinary stuff, like changing
> the parity on-the-fly between two sent characters etc.
Just _specify_ a PC WITH a COM port ?.
Something that needs 1km reach opto isolated Comms does not sound too
'home PC' anyway...
There are plenty of Motherboards made still with COM ports. This PC
has two 9 pin COM ports on the mother using stacked connector technology
to pack in PS2x2, USBx4,Ethernet, VGA, and COMx2 ports into a shrunk case.
The mass school/consumer market may not dictate com ports, but there
are solutions available, and will be for some time.
Simple USB/RS232 converters will always have latency problems, but one
solution is to use more smarts 'in the dongle', so the serial latency is
outside the PC.
Cygnal have a USB+FlashuC that is well suited to this type of
latency reduction.
What WOULD be nice is one with the fastest USB 2.0 speeds :)
-jg
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