[GreenKeys] GreenKeys Digest, Vol 104, Issue 25

[John Nagle]

On 9/16/2012 11:42 AM, greenkeys-request at mailman.qth.net wrote:
> From: "Stan Paddock" <stpaddock at sbcglobal.net> Subject: [GreenKeys]
> RS-232 to current loop To: <greenkeys at mailman.qth.net> Message-ID:
> <D20D89D93ACD4D39A7F414D6FA1C519D at upstairdell> Content-Type:
> text/plain; charset="windows-1252"
> 
> I have noticed a lot of traffic on RS-232 to current loop.
> 
> I have been using a B&B Electronics Model 232CL9R for several years. 
> http://www.bb-elec.com/product11.asp?sku=232CL9R
> 
> While I have not tried it yet, I cannot see why this could not be
> plugged into a USB to RS232 interface cable. 
> http://www.monoprice.com/products/product.asp?seq=1&format=2&p_id=2067&CAWELAID=1329458079&cagpspn=pla&gclid=CO__xP7eurICFeaDQgodk2UAzQ
>
>  Then you could control your ASR 33 with a USB 2.0 connection.
> 
> 
> Stan Paddock San Jose, CA

   The problem is finding a USB to serial converter that will run
as slowly as 45 baud.  That device is actually a StarTech product:

http://www.startech.com/Cards-Adapters/Serial-Cards-Adapters/USB-to-RS232-DB9-Serial-Adapter-Cable-Male-to-Male-Serial-Adapter-USB-to-Serial~ICUSB232

and uses the Prolific PL-2303 USB to serial part.  (Which,
incidentally, is being phased out and will not support Windows 8.)

http://www.prolific.com.tw/US/newsdetail.aspx?news_id=22

Devices that use the Prolific Technologies parts will only go down
to 75 baud.  See page 13 of this data sheet:

http://prolificusa.com/docs/2303/all/ds_PL2303SA_v1.00.pdf

   SIlabs parts will go down to 45 baud, but you have to
use the SILabs programming utility to get them to do that.
That's why I use the SILabs CP2102 evaluation board.  It's possible
to lock in the settings for the SILabs part so that they
can never be changed again, and end user products may do that.
The chip on the eval board isn't locked.

http://www.silabs.com/products/interface/Pages/CP2102EK.aspx

Configuration instructions here:

  http://www.aetherltd.com/connectingusb.html

There may be end user devices which use SILabs chips, but I
haven't found any standalone USB to serial converters that do.
That part seems to be used more as a built-in part for
bigger devices that need USB connectivity.

				John Nagle