Re: UART behavior for CTS/RTS - Kinetis bugs?

From	Hul Tytus <ht@panix.com>
Newsgroups	comp.arch.embedded
Subject	Re: UART behavior for CTS/RTS - Kinetis bugs?
Date	2016-10-28 22:28 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<nv0je4$gh9$1@reader2.panix.com> (permalink)
References	<93dc2e49-2495-4149-8f09-305b9038f599@googlegroups.com>

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Dave - as someone mentioned here, there are all sorts various ways of
using the rs232 uarts. I am currently debugging a file interchange routine 
which is causing all sorts of trouble but it is intended to follow the 
following form, which is a somewhat common setup.
   Two machines are interconnected via a 9 pin cable with the recieve and 
transmit lines switched midway, ala a "null modem". The rts and cts lines 
are switched in the same fashion.
   When either machine is willing to accept data, it raises rts which 
causes cts to be raised at the other machine. When the other machine wants 
to send data, it checks to see cts is high and, if so, transmits as long
as cts is high.

Hul

Dave Nadler <drn@nadler.com> wrote:
> Hi all - Perhaps some of you have encountered this?

> The post linked below shows the Kinetis UART continues to transmit after the receiver has de-asserted CTS:
> https://community.nxp.com/thread/432154
> Freescale engineers claim their part is OK and its the other guys fault...

> Here's my question: As this is an asynchronous link, the receiver can de-assert CTS at any time. What is the transmitter supposed to do? For example, suppose CTS is de-asserted in the middle of transmitting a character: Must the transmitter immediately stop, and restart transmitting the character from the start bit when CTS is again asserted (which in turn introduces a race condition around the end of character transmission)? Or finish the current character transmission and then pause (another race condition for "current character")? Is there any specification on how this should be handled? Or even any consensus?

> Thanks in advance,
> Best Regards, Dave

> PS: I've always used a protocol layer that corrects dropped characters so never had this impact an application, but using some parts like SiLabs bluegiga for SPP don't give that option (at the layer of controlling the Bluetooth device, or supporting a non-protocol client expecting a simple ASCII data stream). Even worse, these things drop status messages into the (application data) stream with no consistent header/delimiter - good luck catching all possible Bluetooth events.

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Thread

UART behavior for CTS/RTS - Kinetis bugs? Dave Nadler <drn@nadler.com> - 2016-10-27 13:21 -0700
  Re: UART behavior for CTS/RTS - Kinetis bugs? Don Y <blockedofcourse@foo.invalid> - 2016-10-27 13:41 -0700
    Re: UART behavior for CTS/RTS - Kinetis bugs? Dave Nadler <drn@nadler.com> - 2016-10-28 10:42 -0700
      Re: UART behavior for CTS/RTS - Kinetis bugs? Don Y <blockedofcourse@foo.invalid> - 2016-10-28 11:15 -0700
        Re: UART behavior for CTS/RTS - Kinetis bugs? Don Y <blockedofcourse@foo.invalid> - 2016-10-28 11:21 -0700
        Re: UART behavior for CTS/RTS - Kinetis bugs? antispam@math.uni.wroc.pl - 2016-10-29 00:17 +0000
          Re: UART behavior for CTS/RTS - Kinetis bugs? Don Y <blockedofcourse@foo.invalid> - 2016-10-28 19:28 -0700
            Re: UART behavior for CTS/RTS - Kinetis bugs? upsidedown@downunder.com - 2016-10-29 13:57 +0300
      Seriial ports on PCs. (was Re: UART behavior for CTS/RTS - Kinetis bugs?) Paul <paul@pcserviceselectronics.co.uk> - 2016-10-29 09:03 +0100
        Re: Seriial ports on PCs. (was Re: UART behavior for CTS/RTS - Kinetis bugs?) upsidedown@downunder.com - 2016-10-29 14:12 +0300
          Re: Seriial ports on PCs. (was Re: UART behavior for CTS/RTS - Kinetis bugs?) Paul <paul@pcserviceselectronics.co.uk> - 2016-10-30 09:34 +0000
  Re: UART behavior for CTS/RTS - Kinetis bugs? Tim Wescott <seemywebsite@myfooter.really> - 2016-10-27 16:39 -0500
    Re: UART behavior for CTS/RTS - Kinetis bugs? Dimiter_Popoff <dp@tgi-sci.com> - 2016-10-28 01:02 +0300
    Re: UART behavior for CTS/RTS - Kinetis bugs? lasselangwadtchristensen@gmail.com - 2016-10-27 15:31 -0700
    Re: UART behavior for CTS/RTS - Kinetis bugs? David Brown <david.brown@hesbynett.no> - 2016-10-28 10:17 +0200
      Re: UART behavior for CTS/RTS - Kinetis bugs? Grant Edwards <invalid@invalid.invalid> - 2016-10-28 14:23 +0000
        Re: UART behavior for CTS/RTS - Kinetis bugs? David Brown <david.brown@hesbynett.no> - 2016-10-28 16:34 +0200
        Re: UART behavior for CTS/RTS - Kinetis bugs? Don Y <blockedofcourse@foo.invalid> - 2016-10-28 12:02 -0700
      Re: UART behavior for CTS/RTS - Kinetis bugs? Don Y <blockedofcourse@foo.invalid> - 2016-10-28 11:50 -0700
      Re: UART behavior for CTS/RTS - Kinetis bugs? upsidedown@downunder.com - 2016-10-29 01:51 +0300
        Re: UART behavior for CTS/RTS - Kinetis bugs? upsidedown@downunder.com - 2016-10-29 13:59 +0300
  Re: UART behavior for CTS/RTS - Kinetis bugs? Wolfgang Mahringer <yeti201@gmx.at> - 2016-10-28 16:45 +0200
  Re: UART behavior for CTS/RTS - Kinetis bugs? Hul Tytus <ht@panix.com> - 2016-10-28 22:28 +0000

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