# RS232\_RXD/TXD on daughtercard interface

**URL:** <https://www.ruby-forum.com/t/rs232-rxd-txd-on-daughtercard-interface/181883>\
**Category:** GNU Radio\
**Created:** [January 19, 2010, 6:48pm UTC](https://www.ruby-forum.com/t/rs232-rxd-txd-on-daughtercard-interface/181883 "2010-01-19T18:48:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ndorphine](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/0ea827/32.png) [@ndorphine](https://www.ruby-forum.com/u/ndorphine)\
**Post date:** [January 19, 2010, 6:48pm UTC](https://www.ruby-forum.com/t/rs232-rxd-txd-on-daughtercard-interface/181883/1 "2010-01-19T18:48:01Z")

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Hi all,  
A while back I noticed there are two signals called RS232\_RXD and  
RS232\_TXD exposed on the PMC connector going to the daughtercard slots  
on the USRP. Tracing these back on the USRP schematic, they go to the  
Cypress EZUSB chip. I searched around a bit but didn’t find any  
reference to any daughtercard using these, nor did grep find any  
reference to these in the 3.2.2 release of GNUradio. Is there any way  
to send/receive UART data to these lines from within GNUradio? If  
not, what was the intent with these lines?

Thanks much…

–  
Regards,  
John O.  
CEO/System Architect  
Epiq Solutions

> **[Epiq Solutions – RF Sensing & Monitoring | Detect Unauthorized Devices](https://epiqsolutions.com/)**
>
> Epiq Solutions is an engineering company that designs
> and develops state of the art Software Defined Radio (SDR) transceiver products
> and applications.

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**Author:** ![ndorphine](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/0ea827/32.png) [@ndorphine](https://www.ruby-forum.com/u/ndorphine)\
**Post date:** [January 19, 2010, 6:59pm UTC](https://www.ruby-forum.com/t/rs232-rxd-txd-on-daughtercard-interface/181883/2 "2010-01-19T18:59:09Z")

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On 01/19/2010 09:41 AM, John O. wrote:

> Thanks much…

Those have never been used. The original intention was to use it as a  
UART. The USRP2 does not connect to those pins, so it’s not a good idea  
to use them.

Matt

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**Author:** ![ndorphine](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/0ea827/32.png) [@ndorphine](https://www.ruby-forum.com/u/ndorphine)\
**Post date:** [January 19, 2010, 7:05pm UTC](https://www.ruby-forum.com/t/rs232-rxd-txd-on-daughtercard-interface/181883/3 "2010-01-19T19:05:00Z")

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On Tue, Jan 19, 2010 at 11:55 AM, Matt E. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > not, what was the intent with these lines?
> > 
> > Thanks much…
> 
> Those have never been used. The original intention was to use it as a UART.  
> The USRP2 does not connect to those pins, so it’s not a good idea to use  
> them.

Gotcha…as always, thanks for the quick reply Matt!

–  
Regards,  
John O.  
CEO/System Architect  
Epiq Solutions  
[www.epiq-solutions.com](http://www.epiq-solutions.com)