Re: ADS1256 - too fast for Linux ?

[Kenneth Heitke <kheitke-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

On 01/14/2011 05:02 AM, Flávio Alberto Lopes Soares wrote:
> Hello all,
> I need to communicate with a Texas Instruments ADS1256 SPI 24 bits ADC (
> http://focus.ti.com/docs/prod/folders/print/ads1256.html) from a 2.6.32
> kernel Linux running on a ARM Samsung S3C2440 microcontroller using spidev
> module, to do this I need to pass a command on MOSI channel and after read
> the result on MISO, but I can't read the correct data from this ADC, the
> data is always corrupted, I believe (but I can't prove this) this occurs
> because the very short time between the command and response, according with
> the component datasheet this time is 50x the clock period, for my circuit
> this is approximately 8us and I believe that there's no time to Linux get
> the interrupt from SPI process this and read the SPI data, my suspicion can
> be correct ? The DMA cannot solve this problem and if true how to know if it
> is activated ? Only Real Time Linux can solve this ?
>
> Thanks for all help
>
> Flavio Alberto Lopes Soares
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Curious if the SPI mode (clock polarity and phase) are set correctly for 
the device that you are communicating with.

Ken

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