RE: [ECOS] serial port ARM e7t problem

RE: [ECOS] serial port ARM e7t problem

[Ravi Kumar B S]

The Samsung microcontroller has a DMA controller with it. the UART can be
configured to work along with the UART chip. This is called DMA mode of the
UART chip. With this you can configure to get the interrupt after certian
number of bytes are received instead of single byte interrupt.

hope this helps.

/Ravi

-----Original Message-----
From: Vinayak P Risbud [mailto:vinayak@multitech.co.in]
Sent: Tuesday, July 16, 2002 7:08 PM
To: Ecos-Discuss
Subject: [ECOS] serial port ARM e7t problem


    Hi,
        I have set, ARM e7t port to Baud 38400,
        I think, the board interrupts the ARM core
        for every character read. (instead of for a
        bunch of characters)
        And because of this,  I am loosing some
        characters, Can anyone give me, any solution
        for this problem ?


        ~
            Vinayak

    ~
        Vinayak


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Re: [ECOS] serial port ARM e7t problem

[Roland Caßebohm]

On Wednesday, 17. July 2002 06:26, Ravi Kumar B S wrote:
> The Samsung microcontroller has a DMA controller with it. the UART can be
> configured to work along with the UART chip. This is called DMA mode of the
> UART chip. With this you can configure to get the interrupt after certian
> number of bytes are received instead of single byte interrupt.

Has anybody tried to do this?
I thinked about it, but I haven't found a way to get an interrupt after a 
timeout like a FIFO does. A UART with FIFO generates an interrupt after 
reaching the triggerlevel or if it received less characters after an timeout. 
Without something like this I will never notify if there are characters but 
the DMA buffer isn't full.
Although there is nothing like a triggerlevel. If the UART gets the last 
character fitting in the DMA-Buffer the interrupt happens and I have to copy 
the buffer and restart the DMA before the next character is coming.
So I have the same chance to loose a character.

Roland

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[ECOS] serial port ARM e7t problem

[Vinayak P Risbud]

    Hi,
        I have set, ARM e7t port to Baud 38400,
        I think, the board interrupts the ARM core
        for every character read. (instead of for a
        bunch of characters)
        And because of this,  I am loosing some
        characters, Can anyone give me, any solution
        for this problem ?


        ~
            Vinayak

    ~
        Vinayak


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RE: [ECOS] serial port ARM e7t problem

[Robert Cragie]

I had a similar problem on the Integrator platform (running out of flash at
a fairly slow speed on an ARM7TDMI) and managed to improve performance by
adding a simple FIFO buffer in the ISR and ensuring Rx interrupts remained
enabled. The DSR then reads out of the FIFO buffer; if further characters
arrive in the time it takes for the DSR to be scheduled, they will go into
the FIFO buffer. The current rudimentary e7t serial driver will keep Rx
interrupts disabled until the DSR completes, which makes it more likely that
overflow in the Rx holding register would occur.

As someone has already pointed out, you could also try using the DMA
somehow, but I can't offer any more advice on this.

Robert Cragie, Design Engineer
________________________________________________________
Jennic Ltd, Furnival Street, Sheffield, S1 4QT,  UK
www.jennic.com Tel: +44 (0) 114 281 2655


> -----Original Message-----
> From: ecos-discuss-owner@sources.redhat.com
> [mailto:ecos-discuss-owner@sources.redhat.com]On Behalf Of Vinayak P
> Risbud
> Sent: 16 July 2002 14:38
> To: Ecos-Discuss
> Subject: [ECOS] serial port ARM e7t problem
>
>
>     Hi,
>         I have set, ARM e7t port to Baud 38400,
>         I think, the board interrupts the ARM core
>         for every character read. (instead of for a
>         bunch of characters)
>         And because of this,  I am loosing some
>         characters, Can anyone give me, any solution
>         for this problem ?
>
>
>         ~
>             Vinayak
>
>     ~
>         Vinayak
>
>
> --
> Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
> and search the list archive: http://sources.redhat.com/ml/ecos-discuss
>
>


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Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
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