Re: serial flow control appears broken

Lee Howard
2007-07-27T18:02:00Z

Alan Cox wrote:

>As the flow control is driven by software on most 16x50 chips (there are
>a couple of exceptions) if we fail to empty the fifo fast enough then any
>flow control will be asserted too late to save the day.
>
>If you stop the application and do the following
>
> cat /dev/ttywhatever
> ^Z
> [stopped]
>
>(so you are asking the OS to buffer data but not ever reading it)
>
>and then fire data at it does the flow control eventually occur ?
>

Yes it does appear to. I told the application to simply sleep(300) at
the appropriate moment, and I watched the application and when it began
the sleep I ran:

cat /dev/ttyS1
(lots of "garbage" began spewing forth)
^Z
(about 2 or 3 seconds and the RTS light goes dark)

Thanks,

Lee.