Linux PC USB to MCU - flow control issues

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TwistOneUp
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Posted by TwistOneUp: Fri. Sep 9, 2016 - 05:24 PM
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hi,

 

i've a bit of confusion on two flow control issues.  data was arriving (but also overrunning) before i added flow control.  now i can't seem to receive a byte.

 

(1) using which signal - the rts signal or the cts signal - tells the sender to begin sending?  i thought i had this down cold but i guess not; and

 

(2) should that signal be high or low to say, "start sending"?  i've seen this both ways, and have heard that some chips (allegedly the MAX232) invert this signal.

 

(3) since the data movement is all from PC to MCU, what to do with the "other" signal?  i.e., if (1) is RTS, do i need to deal with CTS? set it high?  set it low?  throw it away?  and vice-a-versa.

 

tia

 

 

 

 

Tags:

AVR Microcontrollers, AVR XMEGA
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ki0bk
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Posted by ki0bk: Fri. Sep 9, 2016 - 08:23 PM
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Assuming the PC is the DTE, then it asserts RTS, and waits for the DCE to assert CTS....    

I'll leave what assert means to your circuit.  

 

 

Jim

 

 

 

 

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TwistOneUp
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Posted by TwistOneUp: Mon. Sep 12, 2016 - 04:18 PM (Reply to #2)
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thanks!

TOU

 

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steve17
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Posted by steve17: Mon. Sep 12, 2016 - 11:56 PM
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USB RTS/CTS?

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gchapman
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Posted by gchapman: Tue. Sep 13, 2016 - 04:25 AM (Reply to #4)
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Yes.

https://blogs.msdn.microsoft.com/usbcoreblog/2015/07/29/what-is-new-with-serial-in-windows-10/

to

https://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.serialcommunication.aspx

to

https://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.serialcommunication.serialhandshake.aspx?cs-save-lang=1&cs-lang=cpp#code-snippet-1

Multi-platform via pyserial (serial on Python, flow control, browse for USB) :

https://pyserial.readthedocs.io/en/latest/pyserial.html#features

 

Edit : pyserial

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Wed. Sep 14, 2016 - 07:12 AM
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steve17
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Posted by steve17: Tue. Sep 13, 2016 - 07:53 PM (Reply to #5)
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gchapman wrote:

Yes.

https://blogs.msdn.microsoft.com/usbcoreblog/2015/07/29/what-is-new-with-serial-in-windows-10/

to

https://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.serialcommunication.aspx

to

https://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.serialcommunication.serialhandshake.aspx?cs-save-lang=1&cs-lang=cpp#code-snippet-1

 

Okay, I assume this is USB CDC.  Can Win10 send a ZLP?   Can Linux send a ZLP?   If not, it's pretty half-assed, in my opinion.

 

 

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