rs485 on SBC84500 - Embedded

This is a discussion on rs485 on SBC84500 - Embedded ; Hi I'm trying to use the RS485/COM2 port on an embedded Axiom SBC84500 card running kernel 2.4.26. I have configured the JP9,JP10,JP10 according to the documentation but there is no output signal when writing to /dev/ttyS1. I read somewhere that ...

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Thread: rs485 on SBC84500

  1. rs485 on SBC84500

    Hi

    I'm trying to use the RS485/COM2 port on an embedded Axiom SBC84500 card
    running kernel 2.4.26. I have configured the JP9,JP10,JP10 according to the
    documentation but there is no output signal when writing to /dev/ttyS1.

    I read somewhere that I should use ioctls to write to the port instead of
    the standard write function.

    Anybody can help ?

    J.P. Frencia

  2. Re: rs485 on SBC84500

    On 2005-06-18, Frencia wrote:

    > I'm trying to use the RS485/COM2 port on an embedded Axiom
    > SBC84500 card running kernel 2.4.26. I have configured the
    > JP9,JP10,JP10 according to the documentation but there is no
    > output signal when writing to /dev/ttyS1.


    You might have to assert RTS in order to enable the RS-485
    drivers.

    > I read somewhere that I should use ioctls to write to the port
    > instead of the standard write function.


    I really doubt that. I've been doing serial stuff under Unix
    for 15 years, and I've never heard of using ioctl() to write
    data to a serial port.

    --
    Grant Edwards grante Yow! Yow! I'm having a
    at quadraphonic sensation
    visi.com of two winos alone in a
    steel mill!

  3. Re: rs485 on SBC84500

    Grant Edwards wrote:
    > On 2005-06-18, Frencia wrote:
    >
    >
    >>I'm trying to use the RS485/COM2 port on an embedded Axiom
    >>SBC84500 card running kernel 2.4.26. I have configured the
    >>JP9,JP10,JP10 according to the documentation but there is no
    >>output signal when writing to /dev/ttyS1.

    >
    >
    > You might have to assert RTS in order to enable the RS-485
    > drivers.
    >
    >
    >>I read somewhere that I should use ioctls to write to the port
    >>instead of the standard write function.

    >
    >
    > I really doubt that. I've been doing serial stuff under Unix
    > for 15 years, and I've never heard of using ioctl() to write
    > data to a serial port.
    >

    I have. If a sufficient driver was never created, you end up using ioctl
    to control the devices registers directly from user space. It simplifies
    the work of the device developer in exchange for giving the end user a
    headache.
    If the device doesn't have a clean "port" into the linux realm (special
    non 16C550 compliance for example) then it this might be the easy way to
    get a board off the ground.
    T.

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