[CQ-Contest] Computer Interfaces

[Bill Coleman]

On 7/7/01 12:21 AM, Doug Smith W9WI at w9wi at w9wi.com wrote:

>
>> From: Bill Coleman <aa4lr at arrl.net>
>> One thing I believe you ought to consider is eliminating the DB-9 RS-232 
>> interface in favor of a USB interface. There are several good reasons for 
>> this:
>
>I agree with those who think Ethernet is a better successor to serial than
>USB.  Ethernet is cheap (well under $20),

USB cards aren't terribly much more.

>compatible with existing CLI OSs,

You got me there.

>already present in many PCs, and faster than USB. 

USB, at 12 Mbps, is faster than 10BaseT, at 10 Mbps. Although finding 
10BaseT only cards may be hard at this point. 

>And, it can be easily
>shared by several computers on the same bus.  (imagine, being the 10m op at
>a M/M and being able to instantly query all the operating parameters of the
>20m radio)  USB hasn't been around long enough to prove its permanence -
>Ethernet has.

USB has seen widespread adoption since 1998, when it was the only 
expansion option for the iMac. Before that, acceptance was somewhat 
limited. Today, there are gobs of devices which connect by USB.

That said, I see nothing wrong with using Ethernet instead of USB. 
However, USB is pretty simple to directly connect up to a computer. 
(After all, that's how it was designed) 10-100BaseT requires at least a 
hub, or a cross-over Ethernet cable (which are very hard to find), as 
well as more complicated setup (IP addresses, etc).

USB has an architecture that allows drivers to be found and loaded on the 
fly, which pretty much makes setup a snap. (Unless, of course, Microsoft 
writes it....)

>> * The RS-232 interface is an asynchronous, character oriented interface. 
>> There is no error-checking on characters sent or received. Because of 
>
>Not exactly true - the standard allows for parity which is certainly a form
>of error checking.

An insufficient form of error checking -- it only catches single-bit 
errors. From 12 years of working at Hayes, I only remember a few 
instances where parity was even enabled on serial communications systems 
-- and those were rarely checked for errors.

>  For greater reliability, the application and the rig's
>protocol could certainly allow for a checksum/CRC/whatever.  

Yes, but the likelihood of implementing such a protocol is close to NIL 
for a serial interface, whereas it comes with every USB implementation by 
default.



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901


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