Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.arch.embedded > #30366

Re: Linux embedded and direction control of RS485 transceiver

From pozz <pozzugno@gmail.com>
Newsgroups comp.arch.embedded
Subject Re: Linux embedded and direction control of RS485 transceiver
Date 2021-03-25 00:23 +0100
Organization A noiseless patient Spider
Message-ID <s3ghle$n8v$1@dont-email.me> (permalink)
References <s3ds9e$k43$1@dont-email.me> <156tl3wamoufx$.o6pj5sxe57mi$.dlg@40tude.net>

Show all headers | View raw

Il 24/03/2021 11:48, dalai lamah ha scritto:
> Un bel giorno pozz digitò:
> 
>> I have an half-duplex RS485 bus with 10-20 different nodes. Some of them
>> are 8-bit MCU based, one of them could be Linux embedded.
>>
>> It's half-duplex, so it's important for the transmitter node to disable
>> the driver as soon as the last transmitted bit is shifted out.
>>
>> Many small low-cost MCU has interrupt on transmission complete, so the
>> delay of disabling the driver is usually on the order of microseconds.
>>
>> Some new Cortex-M MCUs have an automatic control of external RS485
>> transceiver, so the delay is really zero.
>>
>> What happens in Linux embedded systems? Many of them are based on NXP
>> i.MX CPUs and it seems they aren't able to control the RS485 direction
>> in hardware, but some code is needed. This approach could increase the
>> delay of disabling the driver in the order of milliseconds.
>>
>> Is it possible that a powerful CPU isn't able to control RS485 driver in
>> hardware?
> 
> You should use the RS232 handshake signals (i.e. the RTS signal) in order
> to do that. i.MX UARTs should support them, but it doesn't look very
> straightforward indeed:
> 
> https://community.nxp.com/t5/i-MX-Processors/RTS-CTS-handshake-confusion/m-p/237057

Yes, you can use RTS, but some software MUST change a register bit to 
move that signal!!!

Back to comp.arch.embedded | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Linux embedded and direction control of RS485 transceiver pozz <pozzugno@gmail.com> - 2021-03-24 00:06 +0100
  Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-24 07:28 +0200
    Re: Linux embedded and direction control of RS485 transceiver Don Y <blockedofcourse@foo.invalid> - 2021-03-24 06:17 -0700
      Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-24 17:49 +0200
        Re: Linux embedded and direction control of RS485 transceiver Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-24 18:32 +0200
          Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-24 19:22 +0200
            Re: Linux embedded and direction control of RS485 transceiver David Brown <david.brown@hesbynett.no> - 2021-03-24 19:44 +0100
              Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-25 07:34 +0200
              Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-25 07:47 +0200
            Re: Linux embedded and direction control of RS485 transceiver Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-24 21:13 +0200
              Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-25 07:39 +0200
              Re: Linux embedded and direction control of RS485 transceiver David Brown <david.brown@hesbynett.no> - 2021-03-25 10:48 +0100
                Re: Linux embedded and direction control of RS485 transceiver Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-25 16:33 +0200
                Re: Linux embedded and direction control of RS485 transceiver Grant Edwards <invalid@invalid.invalid> - 2021-03-25 14:49 +0000
                Re: Linux embedded and direction control of RS485 transceiver upsidedown@downunder.com - 2021-03-25 18:43 +0200
                Re: Linux embedded and direction control of RS485 transceiver David Brown <david.brown@hesbynett.no> - 2021-03-26 09:47 +0100
        Re: Linux embedded and direction control of RS485 transceiver Don Y <blockedofcourse@foo.invalid> - 2021-03-24 14:30 -0700
  Re: Linux embedded and direction control of RS485 transceiver dalai lamah <antonio12358@hotmail.com> - 2021-03-24 11:48 +0100
    Re: Linux embedded and direction control of RS485 transceiver pozz <pozzugno@gmail.com> - 2021-03-25 00:23 +0100
  Re: Linux embedded and direction control of RS485 transceiver "A.P.Richelieu" <aprichelieu@gmail.com> - 2021-05-09 13:24 +0200
    Re: Linux embedded and direction control of RS485 transceiver Uwe Bonnes <bon@hertz.ikp.physik.tu-darmstadt.de> - 2021-05-09 12:01 +0000
    Re: Linux embedded and direction control of RS485 transceiver pozz <pozzugno@gmail.com> - 2021-05-10 09:46 +0200

csiph-web