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How to peform SPI DMA on two channels of ADS7863 (or other ADC with two SPI interfaces).

Sanjay52975
Intellectual 465 points
Other Parts Discussed in Thread: ADS7863

Objective:

To obtain simultaneous data from two ADCs within ADS7863 ADC to two SPI buses on OMAP.

 

Architecture:

SDOa and SDOb – Two SPI outputs from ADS7863.

SPI1, SPI2 two SPI devices on OMAPL137.

The two SPI buses are connected as:

 

ADS7863              OMAPL137

SPOa                     SPI1 MISO.

SPOb                     SPI2 MISO

SDI                         SPI1 SIMO

CLK                         SPI 1 CLK

 

NC                          SP1 SIMO

NC                          SPI1 CLK

 

We need two DMA engines (or one) to get simultaneous sampled data from SDOa and SDOb lines connected to SPI1 and SPI2.

 

If this is not the right procedure to obtain simultaneous data from ADS7863 please give us suggestions on how to do this.

(Cross posted on C6747/OMAP forum, since it connectivity issues between ADS7863 and OMAPL137/C6747 DSP.

  • 0
    TI__Guru**** 168605 points

    Sanjay,

    You can configure the ADS7863 to give you data from both ADC channels through SPOa only - that may be one option.  The other would be to set SP2 as an SPI slave and use SPI1 clock as the CLK input to the ADC while wrapping it back to SPI2 clock as well.  That would allow you to use both serial ports at once with a single clock source.