at_91 serial driver (for Atmel AT91RM9200) - Embedded

This is a discussion on at_91 serial driver (for Atmel AT91RM9200) - Embedded ; Hi, I'm wondering about using the Atmel AT91RM9200 under Linux for an embedded application. Among others, I need to run serial communication at 76800 bits/s over one of the USARTs. The RM9200's USARTs have no FIFO and at that speed, ...

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Thread: at_91 serial driver (for Atmel AT91RM9200)

  1. at_91 serial driver (for Atmel AT91RM9200)

    Hi,

    I'm wondering about using the Atmel AT91RM9200 under Linux for an
    embedded application. Among others, I need to run serial communication
    at 76800 bits/s over one of the USARTs.

    The RM9200's USARTs have no FIFO and at that speed, I guess I need DMA
    in order not to loose bytes because of Linux's interrupt latency (>130
    us in some cases I guess).

    I have read that in the serial_usart3 driver used for AVR32
    (http://avr32linux.org/twiki/bin/view...melUsartDriver), the
    incoming DMA "buffer is split in half so that an interrupt fires when
    half the buffer has been filled up and the driver can start consuming
    the data and eventually re-use the buffer. In addition, the USART module
    is set up to fire an interrupt when there is data in the buffer, but no
    additional data has been received within a certain timeout."

    This sounds perfect, then I have to worry neither about the risk of
    delaying too much incoming bytes because the DMA buffer is not full nor
    about loosing some bytes (since I guess that I can choose the size of
    the DMA buffer).

    What I'm wondering is whether the at_91 serial driver which is included
    in the vanilla kernel (I have read it is included in the main tree from
    2.6.16) also does that.

    Does anybody here have some experience with that kind of issues?

    Thanks in advance,

    Best regards,

    Alain Mosnier

  2. Re: at_91 serial driver (for Atmel AT91RM9200)

    BTW, does anyone know why http://www.arm.linux.co.uk/ seems to be down?

    Is there a better newsgroup/mailing list to post questions about such a
    topic (serial driver for ARM9, or more generally for UART without FIFO
    and/or with DMA)?

    Regards,

    Alain Mosnier

  3. Re: at_91 serial driver (for Atmel AT91RM9200)

    http://www.arm.linux.org.uk/

    The mailling at this web site probably the main place for information
    about arm linux. There have been some discussions about a AT91RM9200
    serial port driver that is DMA enabled.

    Alain Mosnier wrote:
    > BTW, does anyone know why http://www.arm.linux.co.uk/ seems to be down?
    >
    > Is there a better newsgroup/mailing list to post questions about such a
    > topic (serial driver for ARM9, or more generally for UART without FIFO
    > and/or with DMA)?
    >
    > Regards,
    >
    > Alain Mosnier



  4. Re: at_91 serial driver (for Atmel AT91RM9200)

    tehn.yit.chin@gmail.com wrote:
    > http://www.arm.linux.org.uk/
    >
    > The mailling at this web site probably the main place for information
    > about arm linux.


    searching this site, I don't find a way to subscribe to the mailing
    lists. How can this be done ?

    Thanks,
    -Michael

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