[OpenIndiana-discuss] stty source code

James Carlson carlsonj at workingcode.com
Thu Sep 6 18:46:29 UTC 2012

Roel_D wrote:
> "never" use USB-> Serial when you're testing something. There is a huge
> difference between products, and the bad products behave very unpredictable.
> Don't forget that the voltage of USB is 5V MAXIMUM but can be much lower
> depending on the hardware, legacy serialports need a good 5V for a logical
> 1. 
> So communication can be disrupted by voltagedrops because the logical 1's
> are not transmitted at the right voltage. 

Good devices have a charge pump to get the standard +/- 12VDC, such as
the MAX232 or SP213.  It wouldn't be too surprising to find "cheap"
designs that lack the charge pump.  :-<

However, you are certainly right that USB serial adapters are in general
all too often substantially less than ideal.  In my experience, it's due
to the layers of software between the actual bits on the wire and the
interface exposed to the application.  If you can get a real serial port
(often not included in modern hardware, but usually available on an
adapter board), you're far, far better off using that.

(Yeah, I'm trying to be charitable with that ...)

James Carlson         42.703N 71.076W         <carlsonj at workingcode.com>

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