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Using RTS\CTS with the USB CDC Virtual Com Port

 
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kcessac



Joined: 28 Aug 2008
Posts: 2

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Using RTS\CTS with the USB CDC Virtual Com Port
PostPosted: Wed Apr 21, 2010 2:21 pm     Reply with quote

I have an application where I need to use RTS (Request To Send) to control serial communications half duplex direction. When RTS is active - transmit, and when RTS is inactive - receive.

Is there a way to read the state of RTS, as well as other control lines, using the CCS USB libraries?

Thanks!
Ttelmah



Joined: 11 Mar 2010
Posts: 19266

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PostPosted: Thu Apr 22, 2010 3:18 pm     Reply with quote

Do you really need to?.
The easiest way, is to have you PIC UART code, setup to look at the required status lines, and if the device to which you are talking goes 'busy', signal that DCD has gone inactive back to the PC.
Going the other way (PC receiving), there is normally no need to control, unless the USB bus has got overloaded, and cannot accept the data. In which case, you just disable CTS, and there is no point in trying to send status information back to the PC, till the USB bus recovers...

Best Wishes
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Fri Apr 23, 2010 2:00 am     Reply with quote

According to the CDC spec, the set_control_line_state request is used to to transmit RTS. It's decoded in the
CCS CDC driver to the structure usb_cdc_carrier, check the sources.
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