splitting RS232

[Fritz Oppliger]

Yo-
I want my 8051 gizmo to talk USB as well as RS232.
I want to use a USB module that looks like a serial port on the USB side
as well as on the 8051 side.
It hooks into the TTL level signal coming from the 8051
The now-existing connection feeds a MAX232.

Question is, can the two talk / listen to the same lines? I don't need
fancy arbitration but simply a way of keeping the MAX232 from blanking all
traffic to/from the USB module and vice versa.
Thanks for hints.

 

[the Wiz]

"Fritz Oppliger" <fritzo_two_@direcway.com> wrote:

Yo-
I want my 8051 gizmo to talk USB as well as RS232.
I want to use a USB module that looks like a serial port on the USB side
as well as on the 8051 side.
It hooks into the TTL level signal coming from the 8051
The now-existing connection feeds a MAX232.

Question is, can the two talk / listen to the same lines? I don't need
fancy arbitration but simply a way of keeping the MAX232 from blanking all
traffic to/from the USB module and vice versa.
Thanks for hints.

There are a number of commercial RS232 splitters (usually listen-only) that are
done using diodes for isolation.

There are some sample Y-cable diagrams here:
http://www.control.com/1026145374/index_html

A commercial "modem data splitter" (serial sharing device) is $55.
http://www.bb-elec.com/product.asp?sku=232MDS&dept_id=129


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