On Jan 7, 2005, at 2:54 PM, Jim Weirich wrote:

> If the Mac has no native RS232 ports, and uses a USB to Serial bridge,  
> one
> must ask:
>
> (1) Does the bridge allow control of the of the RTS/DTR signals,
> (2) is that control exerted through the normal IOCTL calls, and
> (3) Will the bridge communicate changes in a timely enough fashion to
> support the protocol.
>
> If (1) and (2) are true, and (3) is the problem, we could try slowing  
> down
> the protocol (it is somewhat self clocking so timing is real critical).
> Slowing down the procotol would be a simple change in the C code  
> extension
> in the library.

I think the Keyspan adapter supports (1) and (2):

    
http://www.keyspan.com/support/macosx/usa/docs/txtrtf/ 
ReadMeOSXUSA18.txt

I'm not sure I tried that exact unit.

Mike