[Elecraft] serial to USB

Sat Feb 11 18:43:38 EST 2012

Willis,

I would add the fact that the consumer quality USB to Serial adapters do 
not fully implement the RS-232 standard voltages for drivers swinging 
between +25 volts and -25 volts, and receivers that will accept a 
voltage of +3.5 volts or greater as a mark and those of -3.5 volts or 
less as a space.  In addition, the slew rate may not be great enough to 
allow good conversion to real RS-232 levels.

BTW - this situation is nothing new - when the IBM PC was introduced, 
the serial port did not drive the negative level below -5 volts - that 
fact alone reduced the distance the IBM PC could drive RS-232 serial 
lines.  The lack of adherence to standards (voltage levels, timings, 
etc.) has created a bunch of devices that "work", but while not to 
standards, do work in certain common instances - such is the fallout 
from consumer oriented USB to Serial adapters.  As I have mentioned, 
there are commercial versions that "do it right", but they are quite 
"pricy" compared to the consumer variety that will work most of the 
time.  There is a price to be paid for reliability and consistency.  
Make your choices and take whatever "licks" result from them.

73,
Don W3FPR

On 2/11/2012 6:25 PM, WILLIS COOKE wrote:
> Ron, RS-232 serial interface has been defined for at least 25 years and its functions are well known and stable so the radio software and hardware producers can design to these specifications.  The converters are designed to emulate the portion of these functions that the designers feel are needed, but do not conform to any IEEE standard so that other manufacturers can depend on their function.  RS-232 is coded and decoded by hardware, so it is stable.  USB converters are coded by some software and some hardware and are decoded by the RS-232 receiver.  The software portion is somewhat different for the different operating systems.  It takes a while after a new operating system is implemented for the converter writers to get it right.  FTDI and Prolific are two companies who write software and sell chips for USB converters.  Lots of people buy chips from these two companies and mold them into connector/cable assemblies and then retail them under
>   various brands.  It is not real easy to find out which chips have been used and often the end brand does not identify the chip used.  Both of them work OK with most printers, scanners and other serial connected computer stuff, but it can be a different story with ham radio stuff where sometimes more is demanded and RS-232 compliance is usually assumed.  FTDI seems to do a better job than Prolific, but you have to try the software/hardware combination before you know.  I had a lot of trouble when I bought a Win7 computer a couple of years ago and endured some real rude comments from the computer crowd when trying to figure out the combination.  I bought a RS-232 card for my computer and have not had trouble since.  I suspect that the problems with USB converters has been worked out in the two years so that things work better now.  My USB converter that I bought with my K3 in 2007 worked well with the Elecraft software, but not with my loggers.  I
>   understand that the older converters were Prolific and that Elecraft now supplies FTDI, or at least something that will work.  The cards work well with desk top computers, but are not so easy with lap tops that have only USB.  The computer world is trying to get away from RS-232 in favor of USB, but the ham radio community does not want to throw away perfectly good hardware every four or five years like the computer world is geared to do.  Also, ham radio operators expect to know how everything works, computer people not so much.
>   
> Willis 'Cookie' Cooke
> K5EWJ&  Trustee N5BPS, USS Cavalla, USS Stewart
>
>
> ________________________________
>   From: roncasa<roncasa at verizon.net>
> To: elecraft at mailman.qth.net
> Sent: Saturday, February 11, 2012 1:38 PM
> Subject: Re: [Elecraft] serial to USB
>
> It really begs the question for some us who do not understand or are not
> computer geeks:
>
> what IS the difference between FTDI and Prolific.
>
> We understand each one behaving (responding) differently with software
> to radio control, and that some don't work at all, I do not understand
> what makes one preferred over the other (such as elecraft serial/usb
> adaptor cable)
> Prolific also works with most stuff too.
> For example, are they "platform" related? (micr0$oft)
> Is this akin to "ordinary" DVD player as opposed to a "blue ray" player
> that can play "both"??
>
> 72
> Ron, wb1hga
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