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Keystone UART Xon/Xoff

JPH-FR
Intellectual 271 points

Hi,

I need to make a c6678 based board communicate with an existing hardware which works with a serial protocol including Xon/Xoff flow control.

I read the SPRUGP1 documentation (User Guide for Keystone UART), and I find nothing about Xon/Xoff flow control which is a basic functionnality of an UART.


Did I made a bad interpretation of the document or is Xon/Xoff really not supported by the Keystone UART?

Thanks for your response,

JP

  • 0
    TI__Mastermind 42545 points

    Hi JP,

    As I understand it, xon/xoff is a software flow control protocol. The UART subsystem does not support this through hardware. You would have to create a driver that would send the xon or xoff characters.

    Regards, Bill

  • 0 in reply to Bill Taboada
    Expert 1255 points

    I assume your device is sending XOFF to you to beg you to stop sending?  The other way (sending XON/XOFF to the device is easy enough).

    This is going to be a bit unfortunate for you, because you won't be able to use EDMA to receive (too long a latency before you deal with the flow control) and even the FIFO mode will be dicey - you would have to be sure you didn't get stuck with an XON in the FIFO but no interrupt.

    You can run the UART in polling or one-interrupt-per-character mode.  If you can spare a core for this malarkey then fine; otherwise if performance matters and you're designing the board, why not put down an 8 bit PIC and have it mediate the XON/XOFF to hard flow control?

  • 0 in reply to Gordon Deane
    Intellectual 271 points

    Thanks Bill and Gordon for your answers.


    I'm planning to use the UART in one-interrupt per character mode to deal rapidly enought with the flow control.

    Thanks again.

    JP